Liquid-Cooled OptiSpeed Compressor

Speed Drive
Models VSD 270, 292, 351, 385, 419, 424, 503, 608, 658, 704,
790, 868, 882, 917, 948, and 1055. Models LVD 270, 292, 351,
385, 419, 424, 503, 608, 658, 704, and 900.

035-27337-100

Operation Manual Form Number: 160.00-O4 (820)

Issue Date: 2020-08-19 Supersedes: 160.00-O4 (220)
2 Liquid-Cooled OptiSpeed Compressor Speed Drive
 Contents
General safety guidelines.............................................................................................................................. 5
Contes

Safety symbols..................................................................................................................................... 5
Changeability of this document......................................................................................................... 6
Revision notes...................................................................................................................................... 6
Associated literature........................................................................................................................... 6
Conditioned based maintenance...................................................................................................... 7
VSD models.......................................................................................................................................... 8
LVD models........................................................................................................................................ 13
General information.................................................................................................................................... 15
OptiSpeed/Harmonic filter component overview......................................................................... 15
Differences between the G and W designs.................................................................................... 17
Differences for the VSD and LVD model drives............................................................................. 17
OptiSpeed compressor drive control system overview................................................................ 17
VSD adaptive capacity control......................................................................................................... 19
OptiSpeed compressor drive details......................................................................................................... 22
System architecture.......................................................................................................................... 22
Printed circuit boards........................................................................................................................ 32
Safety shutdowns......................................................................................................................................... 34
General information.......................................................................................................................... 34
Safety shutdown messages.............................................................................................................. 35
Cycling shutdowns....................................................................................................................................... 37
General information.......................................................................................................................... 37
Cycling shutdown messages............................................................................................................ 37
Warning messages....................................................................................................................................... 42
General information.......................................................................................................................... 42
Warning messages............................................................................................................................ 42
VSD frequently asked questions................................................................................................................ 43
Unit conversion............................................................................................................................................ 45

Liquid-Cooled OptiSpeed Compressor Speed Drive 3

4 Liquid-Cooled OptiSpeed Compressor Speed Drive
General safety guidelines
Important: Read before proceeding.
This equipment is a relatively complicated apparatus. During rigging, installation, operation,
maintenance, or service, individuals may be exposed to certain components or conditions including,
but not limited to: heavy objects, refrigerants, materials under pressure, rotating components, and
both high and low voltage. Each of these items has the potential, if misused or handled improperly,
to cause bodily injury or death. It is the obligation and responsibility of rigging, installation, and
operating/service personnel to identify and recognize these inherent hazards, protect themselves,
and proceed safely in completing their tasks. Failure to comply with any of these requirements could
result in serious damage to the equipment and the property in which it is situated, as well as severe
personal injury or death to themselves and people at the site.
This document is intended for use by owner-authorized rigging, installation, and operating/service
personnel. It is expected that these individuals possess independent training that will enable them
to perform their assigned tasks properly and safely. It is essential that, prior to performing any
task on this equipment, this individual shall have read and understood the on-product labels, this
document and any referenced materials. This individual shall also be familiar with and comply
with all applicable industry and governmental standards and regulations pertaining to the task in
question.

Safety symbols
The following symbols are used in this document to alert the reader to specific situations:

DANGER

Indicates a possible hazardous situation which will result in death or serious injury if proper care is not
taken.

WARNING

Indicates a potentially hazardous situation which will result in possible injuries or damage to equipment
if proper care is not taken.

CAUTION

Identifies a hazard which could lead to damage to the machine, damage to other equipment and/or
environmental pollution if proper care is not taken or instructions and are not followed.

Note: Highlights additional information useful to the technician in completing the work being
performed properly.

Liquid-Cooled OptiSpeed Compressor Speed Drive 5

 WARNING

External wiring, unless specified as an optional connection in the manufacturer’s product line, is not
to be connected inside the control cabinet. Devices such as relays, switches, transducers and controls
and any external wiring must not be installed inside the micro panel. All wiring must be in accordance
with Johnson Controls’ published specifications and must be performed only by a qualified electrician.
Johnson Controls will NOT be responsible for damage/problems resulting from improper connections
to the controls or application of improper control signals. Failure to follow this warning will void the
manufacturer’s warranty and cause serious damage to property or personal injury.

Changeability of this document

In complying with Johnson Controls’ policy for continuous product improvement, the information
contained in this document is subject to change without notice. Johnson Controls makes no
commitment to update or provide current information automatically to the manual or product
owner. Updated manuals, if applicable, can be obtained by contacting the nearest Johnson
Controls Service office or accessing the Johnson Controls Knowledge Exchange website at https://
docs.johnsoncontrols.com/chillers/.
It is the responsibility of rigging, lifting, and operating/service personnel to verify the applicability
of these documents to the equipment. If there is any question regarding the applicability of these
documents, rigging, lifting, and operating/service personnel should verify whether the equipment
has been modified and if current literature is available from the owner of the equipment prior to
performing any work on the chiller.

Revision notes
Revisions made to this document are indicated in the following table. These revisions are to
technical information, and any other changes in spelling, grammar, or formatting are not included.

Affected pages Description

7 Conditioned Based Maintenance program information added

Associated literature
Form
Manual description
number
Wiring Diagrams - Field Connections YK Style F and G - LV VSD 160.54-PW6
Wiring Diagrams - OptiView Control Center YK Style G and SSS, LV VSD, MV VSD 160.75-PW6
Wiring Diagrams - OptiView Control Center YK Style G and SSS, LV VSD, MV VSD
160.75-PW8
with the LTC I/O Board
Wiring Diagrams - Field Control Modifications YK Style G 160.75-PW4
Wiring Diagrams - Field Connections YK Style H - LV VSD 160.76-PW7
Wiring Diagrams - OptiView Control Center YK Style H and SSS, LV VSD, MV VSD 160.76-PW6
Wiring Diagrams - Field Control Modifications YK Style H 160.76-PW4
Chiller Operation and Maintenance YK Style G 160.75-O1

6 Liquid-Cooled OptiSpeed Compressor Speed Drive

 Form
Manual description
number
Operation OptiView Panel YK Style G 160.54-O1
Chiller Operation and Maintenance YK Style H 160.76-O1
Operation OptiView Panel YK Style H 160.76-O2

Conditioned based maintenance

Traditional chiller maintenance is based upon assumed and generalized conditions. In lieu of
the traditional maintenance program, a Johnson Controls YORK Conditioned Based Maintenance
(CBM) program can be substituted. This CBM service plan is built around the specific needs for
the chiller, operating conditions, and annualized impact realized by the chiller. Your local Johnson
Controls Branch can propose a customized Planned Service Agreement that leverages real time
and historical data, delivering performance reporting, corrective actions required and data enabled
guidance for optimal operation and lifecycle assurance. The program will include fault detection
diagnostics, operation code statistics, performance based algorithms and advance rules based
rationale delivered by the Johnson Controls Connected Equipment Portal.

Liquid-Cooled OptiSpeed Compressor Speed Drive 7

VSD models
Nomenclature, VSD models

Figure 1: Nomenclature, VSD models

W V S D 3 5 1 _ R K F T- 4 6
Voltage Rating: 40 = 400 VAC, 60 Hz
46 = 460 VAC, 60 Hz
50 = 400 VAC, 50 Hz
58 = 575 VAC, 60 Hz
68 = 415 VAC, 50 Hz
Optional 519: Filter-Installed (FT) or Not (_)
Chiller Type: YK (K), YT (T)

Retrofit Package (R), Factory Package (_)

Horsepower Rating: 270, 292, 351, 385, 419, 424, 503, 608
Type of Drive

(W) Asia, (_) Global Design

OptiSpeed™ model part numbers, VSD

The X in the part number below indicates which type of communications is used between the
Micropanel and the OSCD: 1 = YORK Protocol, 7 = MODBUS Protocol, 8 = MODBUS with CPC, W =
Asia (W in the 4th position taking place of the first hyphen in the part number).
Table 1: VSD part numbers and descriptions
Part number
Model Description
60 Hz 50 Hz
VSD270T-40 371-02767-X21 Factory Pack, YT Base Model
VSD270K-40 371-02767-X22 Factory Pack, YK Base Model
VSD270TFT-40 371-02767-X25 Factory Pack, YT Filter Model

270 HP VSD270KFT-40 371-02767-X26 Factory Pack, YK Filter Model

400 VAC VSD270RT-40 371-02767-X31 Retrofit, YT Base Model
VSD270RK-40 371-02767-X32 Retrofit, YK Base Model
VSD270RTFT-40 371-02767-X35 Retrofit, YT Filter Model
VSD270RKFT-40 371-02767-X36 Retrofit, YK Filter Model
VSD292T-50 371-03700-X01 Factory Pack, YT Base Model
VSD292K-50 371-03700-X02 Factory Pack, YK Base Model
VSD292TFT-50 371-03700-X05 Factory Pack, YT Filter Model
VSD292KFT-50 371-03700-X06 Factory Pack, YK Filter Model

292 HP VSD292RT-50 371-03700-X11 Retrofit, YT Base Model

400 VAC VSD292RK-50 371-03700-X12 Retrofit, YK Base Model
VSD292RTFT-50 371-03700-X15 Retrofit, YT Filter Model
VSD292RKFT-50 371-03700-X16 Retrofit, YK Filter Model
W-VSD292K-50 371W06040-X02 Factory Pack, YK Base Model
W-VSD292KFT-50 371W06040-X06 Factory Pack, YK Filter Model

8 Liquid-Cooled OptiSpeed Compressor Speed Drive

Table 1: VSD part numbers and descriptions
Part number
Model Description
60 Hz 50 Hz
VSD292T-68 371-03700-X21 Factory Pack, YT Base Model
VSD292K-68 371-03700-X22 Factory Pack, YK Base Model
VSD292TFT-68 371-03700-X25 Factory Pack, YT Filter Model
VSD292KFT-68 371-03700-X26 Factory Pack, YK Filter Model

292 HP VSD292RT-68 371-03700-X31 Retrofit, YT Base Model

415 VAC VSD292RK-68 371-03700-X32 Retrofit, YK Base Model
VSD292RTFT-68 371-03700-X35 Retrofit, YT Filter Model
VSD292RKFT-68 371-03700-X36 Retrofit, YK Filter Model
W-VSD292K-68 371W06040-X22 Factory Pack, YK Base Model
W-VSD292KFT-68 371W06040-X26 Factory Pack, YK Filter Model
VSD351T-46 371-02767-X01 Factory Pack, YT Base Model
VSD351K-46 371-02767-X02 Factory Pack, YK Base Model
VSD351TFT-46 371-02767-X05 Factory Pack, YT Filter Model

351 HP VSD351KFT-46 371-02767-X06 Factory Pack, YK Filter Model

460 VAC VSD351RT-46 371-02767-X11 Retrofit, YT Base Model
VSD351RK-46 371-02767-X12 Retrofit, YK Base Model
VSD351RTFT-46 371-02767-X15 Retrofit, YT Filter Model
VSD351RKFT-46 371-02767-X16 Retrofit, YK Filter Model
VSD385T-40 371-03789-X21 Factory Pack, YT Base Model
VSD385K-40 371-03789-X22 Factory Pack, YK Base Model
VSD385TFT-40 371-03789-X23 Factory Pack, YT Filter Model

385 HP VSD385KFT-40 371-03789-X24 Factory Pack, YK Filter Model

400 VAC VSD385RT-40 371-03789-X31 Retrofit, YT Base Model
VSD385RK-40 371-03789-X32 Retrofit, YK Base Model
VSD385RTFT-40 371-03789-X33 Retrofit, YT Filter Model
VSD385RKFT-40 371-03789-X34 Retrofit, YK Filter Model

Liquid-Cooled OptiSpeed Compressor Speed Drive 9

Table 1: VSD part numbers and descriptions
Part number
Model Description
60 Hz 50 Hz
VSD419T-50 371-03789-X05 Factory Pack, YT Base Model
VSD419K-50 371-03789-X06 Factory Pack, YK Base Model
VSD419TFT-50 371-03789-X07 Factory Pack, YT Filter Model
VSD419KFT-50 371-03789-X08 Factory Pack, YK Filter Model
VSD419RT-50 371-03789-X15 Retrofit, YT Base Model
VSD419RK-50 371-03789-X16 Retrofit, YK Base Model
VSD419RTFT-50 371-03789-X17 Retrofit, YT Filter Model
VSD419RKFT-50 371-03789-X18 Retrofit, YK Filter Model

419 HP W-VSD419K-50 371W06431-X06 Factory Pack, YK Base Model

400 VAC W-VSD419KFT-50 371W06431-X08 Factory Pack, YK Filter Model
W-VSD419T-50 371-05395-X05 Factory Pack, YT Base Model
W-VSD419K-50 371-05395-X06 Factory Pack, YK Base Model
W-VSD419TFT-50 371-05395-X07 Factory Pack, YT Filter Model
W-VSD419KFT-50 371-05395-X08 Factory Pack, YK Filter Model
W-VSD419RT-50 371-05395-X15 Retrofit, YT Base Model
W-VSD419RK-50 371-05395-X16 Retrofit, YK Base Model
W-VSD419RTFT-50 371-05395-X17 Retrofit, YT Filter Model
W-VSD419RKFT-50 371-05395-X18 Retrofit, YK Filter Model
VSD419T-68 371-03789-X25 Factory Pack, YT Base Model
VSD419K-68 371-03789-X26 Factory Pack, YK Base Model
VSD419TFT-68 371-03789-X27 Factory Pack, YT Filter Model
VSD419KFT-68 371-03789-X28 Factory Pack, YK Filter Model

419 HP VSD419RT-68 371-03789-X35 Retrofit, YT Base Model

415 VAC VSD419RK-68 371-03789-X36 Retrofit, YK Base Model
VSD419RTFT-68 371-03789-X37 Retrofit, YT Filter Model
VSD419RKFT-68 371-03789-X38 Retrofit, YK Filter Model
W-VSD419K-68 371W06431-X26 Factory Pack, YK Base Model
W-VSD419KFT-68 371W06431-X28 Factory Pack, YK Filter Model
VSD424T-58 371-04881-X01 Factory Pack, YT Base Model
VSD424K-58 371-04881-X02 Factory Pack, YK Base Model
VSD424TFT-58 371-04881-X03 Factory Pack, YT Filter Model

424 HP VSD424TFK-58 371-04881-X04 Factory Pack, YK Filter Model

575 VAC VSD424RT-58 371-04881-X11 Retrofit, YT Base Model
VSD424RK-58 371-04881-X12 Retrofit, YK Base Model
VSD424RTFT-58 371-04881-X13 Retrofit, YT Filter Model
VSD424RTFK-58 371-04881-X14 Retrofit, YK Filter Model

10 Liquid-Cooled OptiSpeed Compressor Speed Drive

Table 1: VSD part numbers and descriptions
Part number
Model Description
60 Hz 50 Hz
VSD503T-46 371-03789-X01 Factory Pack, YT Base Model
VSD503K-46 371-03789-X02 Factory Pack, YK Base Model
VSD503TFT-46 371-03789-X03 Factory Pack, YT Filter Model

503 HP VSD503TFK-46 371-03789-X04 Factory Pack, YK Filter Model

460 VAC VSD503RT-46 371-03789-X11 Retrofit, YT Base Model
VSD503RK-46 371-03789-X12 Retrofit, YK Base Model
VSD503RTFT-46 371-03789-X13 Retrofit, YT Filter Model
VSD503RTFK-46 371-03789-X14 Retrofit, YK Filter Model
VSD608K-40 371-06982-X22 Factory Pack, YK Base Model

608 HP VSD608KFT-40 371-06982-X24 Factory Pack, YK Filter Model

380 VAC VSD608RK-40 371-06982-X32 Retrofit, YK Base Model
VSD608RKFT-40 371-06982-X34 Retrofit, YK Filter Model
VSD608K-42 371-06982-X46 Factory Pack, YK Base Model

608 HP VSD608KFT-42 371-06982-X48 Factory Pack, YK Filter Model

400 VAC VSD608RK-42 371-06982-X56 Retrofit, YK Base Model
VSD608RKFT-42 371-06982-X58 Retrofit, YK Filter Model
VSD608T-58 371-04563-X01 Factory Pack, YT Base Model
VSD608K-58 371-04563-X02 Factory Pack, YK Base Model
VSD608TFT-58 371-04563-X03 Factory Pack, YT Filter Model

608 HP VSD608KFT-58 371-04563-X04 Factory Pack, YK Filter Model

575 VAC VSD608RT-58 371-04563-X11 Retrofit, YT Base Model
VSD608RK-58 371-04563-X12 Retrofit, YK Base Model
VSD608RTFT-58 371-04563-X13 Retrofit, YT Filter Model
VSD608RKFT-58 371-04563-X14 Retrofit, YK Filter Model
VSD658K-50 371-06982-X06 Factory Pack, YK Base Model
VSD658KFT-50 371-06982-X08 Factory Pack, YK Filter Model

658 HP VSD658RK-50 371-06982-X16 Retrofit, YK Base Model

380 VAC VSD658RKFT-50 371-06982-X18 Retrofit, YK Filter Model
W-VSD658K-50 371W06212-X02 Factory Pack, YK Base Model
W-VSD658KFT-50 371W06212-X04 Factory Pack, YK Filter Model
VSD658K-43 371-06982-X62 Factory Pack, YK Base Model

658 HP VSD658KFT-43 371-06982-X64 Factory Pack, YK Filter Model

400 VAC VSD658RK-43 371-06982-X72 Retrofit, YK Base Model
VSD658RKFT-43 371-06982-X74 Retrofit, YK Filter Model
VSD704K-68 371-06982-X26 Factory Pack, YK Base Model
VSD704KFT-68 371-06982-X28 Factory Pack, YK Filter Model

704 HP VSD704RK-68 371-06982-X36 Retrofit, YK Base Model

415 VAC VSD704RKFT-68 371-06982-X38 Retrofit, YK Filter Model
W-VSD704K-68 371W06212-X22 Factory Pack, YK Base Model
W-VSD704KFT-68 371W06212-X24 Factory Pack, YK Filter Model

Liquid-Cooled OptiSpeed Compressor Speed Drive 11

Table 1: VSD part numbers and descriptions
Part number
Model Description
60 Hz 50 Hz
VSD790K-46 371-06982-X02 Factory Pack, YK Base Model

790 HP VSD790KFT-46 371-06982-X04 Factory Pack, YK Filter Model

460 VAC VSD790RK-46 371-06982-X12 Retrofit, YK Base Model
VSD790RKFT-46 371-06982-X14 Retrofit, YK Filter Model
VSD868K-50 371-06863-X06 Factory Pack, YK Base Model

868 HP VSD868KFT-50 371-06863-X08 Factory Pack, YK Filter Model

380 VAC VSD868RK-50 371-06863-X16 Retrofit, YK Base Model
VSD868RKFT-50 371-06863-X18 Retrofit, YK Filter Model
VSD882K-40 371-06863-X22 Factory Pack, YK Base Model

882 HP VSD882KFT-40 371-06863-X24 Factory Pack, YK Filter Model

380 VAC VSD882RK-40 371-06863-X32 Retrofit, YK Base Model
VSD882RKFT-40 371-06863-X34 Retrofit, YK Filter Model
VSD914K-43 371-06863-X62 Factory Pack, YK Base Model

914 HP VSD914KFT-43 371-06863-X64 Factory Pack, YK Filter Model

400 VAC VSD914RK-43 371-06863-X72 Retrofit, YK Base Model
VSD914RKFT-43 371-06863-X74 Retrofit, YK Filter Model
VSD917K-42 371-06863-X46 Factory Pack, YK Base Model

917 HP VSD917KFT-42 371-06863-X48 Factory Pack, YK Filter Model

400 VAC VSD917RK-42 371-06863-X56 Retrofit, YK Base Model
VSD917RKFT-42 371-06863-X58 Retrofit, YK Filter Model
VSD948K-68 371-06863-X26 Factory Pack, YK Base Model

948 HP VSD948KFT-68 371-06863-X28 Factory Pack, YK Filter Model

415 VAC VSD948RK-68 371-06863-X36 Retrofit, YK Base Model
VSD948RKFT-68 371-06863-X38 Retrofit, YK Filter Model
VSD1055K-46 371-06863-X02 Factory Pack, YK Base Model
1055 HP VSD1055KFT-46 371-06863-X04 Factory Pack, YK Filter Model
460 VAC VSD1055RK-46 371-06863-X12 Retrofit, YK Base Model
VSD1055RKFT-46 371-06863-X14 Retrofit, YK Filter Model

12 Liquid-Cooled OptiSpeed Compressor Speed Drive

LVD models
Nomenclature, LVD models

Figure 2: Nomenclature, LVD models

LVD 0503 G R N01 K C 30 B 06 L Z - 46 A

I II III IV V VI VII VIII IX X XI XII XIII XIV

I - Drive Type VIII - Liquid DWP

LVD 15 = 150 psig
(historical models) 30 = 300 psig
VSD * = Not yet defined
TM
HYP IX - Input Connection
D = Disconnect Switch
II - Horsepower and Amp Rating B = Circuit Breaker
(4 digits fixed length) T = Terminal Block
* = Not yet defined
III - Design Center/Source
G = Global Design X - Input Connection Rating
W = Asia Design 04 = 400 A
T = Toshiba 06 = 600 A
B = Benshaw 08 = 800 A
10 = 1000 A
IV - VSD Mounting Method 12 = 1200 A
00 = None (terminal block)
X = Unit Mount (Factory Pack) * = Not yet defined
R = Remote Mount (Floor Standing)
XI - Code Agency Approval
V - Enclosure Type Rating
L = cUL/cETL
N01 = NEMA 1 C = CE
N04 = NEMA4 G =GB
N3R = NEMA 3R Q = Special
I33 = IP33 X = None
*** = Not yet defined
XII - Harmonic Mitigation
VI - Chiller Type
F = Filter Model
H = YMC2 (YH) Z = Base Model
K = YK A = Active Front End Model
T = YT
XIII - Input Voltage/Frequency
VII - Chiller Cooling Method/VSD Cooling (Per M-527)
Medium
40 = 380/400 V 60 Hz
C = Condenser liquid cooled / water 50 = 380/400 V 50 Hz
E = Evaporator liquid cooled / water 42 = 400 V 60 Hz
D = Condenser liquid cooled / glycol 46 = 460 V 60 Hz
F = Evaporator liquid cooled / glycol 68 = 415 V 50 Hz
B = Air cooled / glycol 58 = 575 V 60 Hz
A = Air cooled / air
R = Refrigerant / refrigerant
* = Not yet defined XIV - Product Mod Level Suffix
A = Mod Level "A"
B = Mod Level "B"

Liquid-Cooled OptiSpeed Compressor Speed Drive 13

OptiSpeed™ model part numbers, LVD
The X in the part number below indicates which type of communications is used between the
Micropanel and the OSCD: 1 = YORK Protocol, 7 = MODBUS Protocol, 8 = MODBUS w/ CPC, W = Asia
(4th position taking place of the first hyphen in the part number).
Table 2: LVD part numbers and descriptions
Model number Part number Description
270 HP – 60 HZ, 380 – 400 VAC LVD0270GXN01KC30B04LZ-40A 371-06976-X22 Factory Pack, YK Chiller
270 HP – 60 HZ, 400 VAC LVD0270GXN01KC30B04LZ-42A 371-06976-X46 Factory Pack, YK Chiller (Saudi)
292 HP – 50 HZ, 400 VAC LVD0292WXI22KC30B04GZ-50A 371W06640-X02 Factory Pack, YK Chiller
292 HP – 50 HZ, 380 – 400 VAC LVD0292GXN01KC30B04LZ-50A 371-06976-X06 Factory Pack, YK Chiller
292 HP – 50 HZ, 415 VAC LVD0292WXI22KC30B04GZ-68A 371W06640-X22 Factory Pack, YK Chiller
292 HP – 50 HZ, 415 VAC LVD0292GXN01KC30B04LZ-68A 371-06976-X26 Factory Pack, YK Chiller
351 HP – 60 HZ, 460 VAC LVD0315GXN01KC30B04LZ-46A 371-06976-X02 Factory Pack, YK Chiller
385 HP – 60 HZ, 380 – 400 VAC LVD0385GXN01KC30B06LZ-40A 371-06697-X22 Factory Pack, YK Chiller
385 HP – 60 HZ, 400 VAC LVD0385GXN01KC30B06LZ-42A 371-06697-X46 Factory Pack, YK Chiller
419 HP – 50 HZ, 380 – 400 VAC LVD0419GXN01KC30B06LZ-50A 371-06697-X06 Factory Pack, YK Chiller
419 HP – 50 HZ, 400 VAC LVD0419WXI22KC30B06GZ-50A 371W06642-X06 Factory Pack, YK Chiller
419 HP – 50 HZ, 415 VAC LVD0419WXI22KC30B06GZ-68A 371W06642-X26 Factory Pack, YK Chiller
419 HP – 50 HZ, 415 VAC LVD0419GXN01KC30B06LZ-68A 371-06697-X26 Factory Pack, YK Chiller
424 HP – 60 HZ, 575 VAC LVD0424GXN01KC30B04LZ-58A 371-06976-X42 Factory Pack, YK Chiller
503 HP – 60 HZ, 460 VAC LVD0503GXN01KC30B06LZ-46A 371-06697-X02 Factory Pack, YK Chiller
608 HP – 60 HZ, 575 VAC LVD0608GXN01KC30B06LZ-58A 371-06697-X42 Factory Pack, YK Chiller
658 HP – 50 HZ, 400 VAC LVD0658WXI22KC30B10GZ-50A 371W06644-X02 Factory Pack, YK Chiller
704 HP – 50 HZ, 415 VAC LVD0704WXI22KC30B10GZ-68A 371W06644-X22 Factory Pack, YK Chiller
900 HP – 50 HZ, 400 VAC LVD0900WXI22KC30B12GZ-50A 371W06646-X02 Factory Pack, YK Chiller
900 HP – 50 HZ, 415 VAC LVD0900WXI22KC30B12GZ-68A 371W06646-X22 Factory Pack, YK Chiller

14 Liquid-Cooled OptiSpeed Compressor Speed Drive

General information
This instruction is to be used in conjunction with the Operation Instructions for YORK Centrifugal
chillers furnished with an optional YORK® OptiSpeed™ Compressor Drive (OSCD).

OptiSpeed/Harmonic filter component overview

OptiSpeed compressor drive 270, 292, 351, and 424 hp (low horsepower
model)
The OSCD is a liquid cooled, transistorized, pulse- width modulation (PWM) inverter in a highly
integrated package. This package is small enough to mount directly onto the chiller motor, and
small enough to be applied in many retrofit chiller applications. The power section of the drive is
composed of four major blocks: an AC to DC rectifier section with an integrated precharge circuit, a
DC bus filter section, a three-phase DC to AC inverter section and an output suppression network.
An electronic circuit breaker with ground fault sensing connects the AC line to an AC line inductor
and then to the DC converter. The line inductor will limit the amount of fault current so that the
electronic circuit breaker is sufficient for protecting the OSCD. Input fuses to the OSCD are no
longer needed. The following description of operation is specific for the 351 hp OSCD unless
otherwise noted.
The AC to DC converter uses three Silicon Controlled Rectifiers (SCRs) and three diodes. One SCR
and one diode are contained in each module. Three modules are required to converter the three-
phase input AC voltage into DC voltage. The modules are mounted on the bot- tom of the liquid
cooled heatsink.
The use of the SCRs in the converter permits precharge of the DC bus capacitors when the chiller
enters the prelube cycle. It also provides a fast disconnect from the AC line when the chiller
enters the coastdown cycle. At this time, the OSCD is turned off, the SCRs in the converter are no
longer turned on and remain in a turned off condition until the next precharge cycle. The DC bus
capacitors will start to discharge through the bleeder resistors. When the chiller enters the pre-lube
cycle, the OSCD is commanded to precharge and the SCRs are gradually turned on to slowly charge
the DC bus capacitors. This is called the precharge period, which last for 20 seconds. At this time the
SCRs are fully turned on. The SCR Trigger board provides the turn on commands for the SCRs. The
OSCD Logic board provides the command to the SCR trigger board when to precharge.

WARNING

Although many of these parts are similar to the parts used in previous Variable Speed Drive (VSD)
designs, these parts are only compatible with drives having the base part numbers included on
the cover of this form. Failure to use the correct parts may cause major damage to these and other
components in the drive.

For example, the VSD logic board 031-02077-000 used in this drive is not compatible with 031-01433-000
logic board used in previous designs. A new VSD logic board was designed in 2006. The part number
of the new board is 031-02506-002. The part number of the new board for the 575 VAC application
is 031-02506-003. The software is not interchangeable between the 575 VAC version and all other
applications. Also the software is not interchangeable be- tween the 031-01433, 031-02077, or the
031-02506 boards.

The DC Bus filter section of the drive consists of one basic component, a series of electrolytic
filter capacitors. The capacitors provide a large energy reservoir for use by the DC to AC inverter
section of the OSCD. The capacitors are contained in the OSCD Power Unit. “Bleeder” resistors are

Liquid-Cooled OptiSpeed Compressor Speed Drive 15

mounted on the side of the Power Unit to provide a discharge path for the stored energy in the
capacitors.
The DC to AC inverter section of the OSCD serves to convert the DC voltage to AC voltage at the
proper magnitude and frequency as commanded by the OSCD Logic board. The inverter section is
actually composed of one power unit. This power unit contains one very fast switching transistor
module mounted on the same liquid cooled heatsink as the converter modules, the DC Bus
capacitors, and an OSCD Gate Driver board. The gate driver board provides the turn on and turn
off commands to the output transistors. The OSCD Logic board determines when the turn on and
turn off commands should occur. The gate driver board is mounted directly on top of the transistor
module, and it is held in place with mounting screws and soldered to the transistor module.
The OSCD output suppression network is composed of a series of capacitors and resistors. The job
of the suppressor network is to increase the time it takes for the output voltage to switch as seen
by the motor, and reduce the peak voltage applied to the motor windings. This network protects
the compressor motor from problems commonly associated with PWM motor drives.
Other sensors and boards are used to provide safe operation of the OSCD. The transistor module
and heatsink have thermistors mounted on them to provide temperature information to the OSCD
logic board. These sensors protect the OSCD from over temperature conditions. A Bus Voltage
Isolator board is used to ensure that the DC bus capacitors are properly charged. Three output
current transformers protect the OSCD and motor from over current conditions.

OSCD 385, 419, 503, 608, 658, 704, 790, 868, 882, 914, 917, 948, and 1055 hp
(high horsepower model)
The high horsepower models' OSCDs function in the same manner as the low horsepower models,
and have the same basic components. The power requirements of these high horsepower drives
require more capacitors in the DC Bus and 3-output transistor sections are needed. One section is
used for each output phase. Each transistor module within the output transistor section contains a
thermistor, which is connected to the OSCD logic board. The transistor gate driver board is mount-
ed on top of the transistor section in the same manner as the low horsepower model, but it only
contains two transistor drivers. The modules and gate driver boards are not interchangeable
between the various models.

Harmonic filter option

The VSD model of OSCD system may also include an optional harmonic filter and high frequency
trap designed to meet the IEEE Std 519, IEEE Recommended Practices and Requirements for Harmonic
Control in Electrical Power Systems. The harmonic filter is offered as a method to improve the input
current wave- form drawn by the OSCD from the AC line. In this way, it reduces the possibility of
causing electrical interference with other sensitive electronic equipment connected to the same
power source. An additional benefit of the optional harmonic filter is that it will correct the system
power factor to nearly unity.
The power section of the Harmonic Filter is composed of three major blocks: a precharge section, a
three-phase inductor, and a Filter Power Unit.
The precharge section contains precharge resistors, a precharge contactor, and a supply contactor.
The pre-charge network serves two purposes, to slowly charge the DC bus capacitors associated
with the Filter Power Unit, and to provide a means of disconnecting the filter power unit from the
AC line. When the chiller is turned off, both contactors are de-energized and the filter power unit is
disconnected from the AC line. When the chiller starts to run, the precharge resistors are switched
into the circuit by the precharge contactor for a fixed time period of 5 seconds. This permits the
filter capacitors in the filter power unit to slowly charge. After the 5-second time period, the supply
contactor is energized and the precharge contactor is de-energized, permitting the filter power
unit to completely charge. Three power fuses connect the filter power components to the AC line.
Very fast semiconductor power fuses are used to quickly disconnect the transistor module from the
power source if a catastrophic failure were to occur on the DC bus of the filter power unit.

16 Liquid-Cooled OptiSpeed Compressor Speed Drive

The three-phase inductor provides some impedance for the filter to “work against”. It effectively
limits the rate of change in current at the input to the filter to a reason- able level.
The Filter Power Unit is the most complicated power component in the optional filter. Its purpose
is to generate the harmonic currents required by the OSCD’s AC-to-DC converter so that these
harmonic currents are not drawn from the AC line. The Filter Power Unit is identical to the OSCD's
Power Unit in the 351 hp drive, except for two fewer capacitors in the filter capacitor “bank”, and
a smaller transistor module and modified gate driver board. The Harmonic Filter Gate Driver
board provides turn on and turn off commands as determined by the Harmonic Filter Logic board.
“Bleeder” resistors are mounted on the side of the Filter Power Unit to provide a discharge path for
the DC bus capacitors.
Other sensors and boards are used to provide safe operation of the harmonic filter. The transistor
module contains a temperature sensor that provides temperature information back to the Filter
Logic Board. This sensor protects the filter transistor module from over temperature conditions.
A Bus Isolator board is used to ensure that the DC bus capacitors are properly charged and the
voltage is balanced. Two output current sensors are used to protect the filter against an over
current or an overload condition. Input current transformers sense the input current drawn by the
OSCD’s AC to DC converter. The Line Voltage Isolation board provides AC line voltage information
to the Harmonic Filter Logic board. This information is used to determine the proper bus voltage
value.
The “trap” filter is standard on all OSCD's that contain an optional Harmonic Filter. The “trap” filter
is composed of a series of capacitors, inductors, and resistors. The “trap” filter is used to reduce the
effects of the PWM switching frequency of the filter on the power source.

Differences between the G and W designs

The drive model number nomenclature has two different letters for the design center of the drive.
The G for the design center is a drive that is designed to the UL and CE requirements. The W for the
design center is a drive that is designed to standards that govern products built for the Asia market.
The way the drive functions, protects itself, and the motor are the same for both designs. The W
design takes advantage of local components, and local manufacturing. The cooling system is the
area where most of the changes occur and only effect the 50 Hz application. The W design solves
the problem of reduce cooling because of 50 Hz power by using a large cooling fan and a different
cooling pump. The cooling fan and pump require a 230 VAC 50 Hz source. This higher power source
allows the fan and pump to provide the same amount of cooling as the 60 Hz application. The
230 VAC source is provided by an additional voltage tap from the control transformer. This new
transformer provides the voltage required for the 230 VAC and 120 VAC components.

Differences for the VSD and LVD model drives

The VSD model drives are designed so that the harmonic filter system can be included in the
drive enclosure. The VSD model also contains the control wiring, additional cooling capacity, and
precharge resistors for the harmonic filter system, regardless if the harmonic filter system is
installed or not. This process allowed for an easier method to retrofit the harmonic filter system
later if the customer desired. The LVD model does not contain any support for the harmonic filter
system. The enclosure size is reduced, and the harmonic filter cannot be added as an option later.
The function of the drive is identical between the two designs.

OptiSpeed compressor drive control system overview

The OSCD control system can be connected to a Microcomputer Control Center or to an OptiView
Control Center. Regardless of which control center is used each component performs the same
function.

Liquid-Cooled OptiSpeed Compressor Speed Drive 17

The OSCD control system is composed of various components located within both the Control
Center and the OSCD. In this way, the Control Center integrates with the OSCD. The OSCD system
uses various microprocessors, which are linked together through a network of communications
links.

The Control Center before 2005

The Control Center contains two boards that act upon OSCD related information, the Microboard
and the Adaptive Capacity Control board (ACC). The ACC board performs two major functions in the
OSCD control system:

• To act as a gateway for information flow between the Control Center and the OSCD
• To determine the optimum operating speed for maximum chiller system efficiency

The ACC board acts as an information gateway for all data flowing between the OSCD and the
Control Center. The ACC board has a communication link to the OSCD logic board, and one
communication link from the optional Harmonic Filter logic board. When the ACC board receives
the information, the information is passed onto the Control Center by a software communication
link. The Microcomputer Control Center communicates in a parallel fashion through two ribbon
cables connecting the ACC board to the Microboard. The OptiView™ Control Center communicates
through communications port through a bidirectional serial port through a three-wire cable that
connects the ACC board to the Microboard.
To achieve the most efficient operation of a centrifugal compressor, the speed of the compressor
must be reduced to match the lift or head of the load. This lift or head is determined by the
evaporator and condenser refrigerant pressures. However, if the compressor speed is reduced
too much, the refrigerant gas will flow backwards through the compressor wheel causing the
compressor to surge, which is an undesirable and extremely inefficient operating condition. As
a result, one particular optimum operating speed exists (on the edge of surge) for a given head,
which provides the optimum system efficiency.
The compressor’s inlet guide vanes, which are used in fixed speed applications to control the
amount of refrigerant gas flowing through the compressor, are controlled together with the
compressor speed on an OSCD chiller system to obtain the required chilled liquid temperature
while simultaneously requiring minimum power from the AC line.
The ACC board automatically generates its own “Adaptive”three-dimensional surge surface map
while the chiller system is in operation. This “Adaptive” operation is accomplished through the
use of a patented surge detection algorithm. The novel surge detection system uses pressure
information obtained from the chiller’s two pressure transducers or the OSCD’s instantaneous
power output to determine if the system is in surge. The adaptive system permits construction of
a customized compressor map for each individual chiller system. The benefits of this new adaptive
system include the following:

• A customized compressor map for each chiller that eliminates inefficient operation due to the
safety margin built into the previous designs to compensate for compressor manufacturing
tolerances
• The ability to update the system’s surge surface as the unit ages
• Automatic updating of the compressor map if changes in refrigerant are implemented at a
later date

The Control Center beginning in 2005

A major change in the control system took place in 2005. Several redesigns took place in the
OptiView panel and the OSCD. The redesign replaced microprocessors that were becoming
obsolete. This was a time to take advantage of new components that were now available. An
additional communications port was added so that the communications between the microboard

18 Liquid-Cooled OptiSpeed Compressor Speed Drive

and the OSCD logic board is faster. In the changes to the microboard the function of the Adaptive
Capacity Board was placed into the microboard, and the ACC board was longer needed in new
production. The new microboard is also compatible with the older designs microboards used in the
OptiView panel. The new OSCD logic also added this new communication port, but also retained all
of the functions required to still communicate with the ACC board.

OptiSpeed and optional harmonic filter logic control boards

Within the enclosure of the VSD model drive, the OSCD logic board and optional Harmonic Filter
logic board are interconnected by a 16-position ribbon cable. This cable provides power for the
Filter logic board and a method of communications between the two boards.
The OSCD Logic board performs numerous functions, control of the OSCD’s cooling fans and
pumps, when to precharge the bus capacitors, and generates the PWM.
The OSCD Logic board also determines shutdown conditions by monitoring the three phases of
motor current, heatsink temperature, baseplate temperature, internal ambient temperature, and
the DC bus voltage.
The optional Harmonic Filter logic board determines when to precharge the harmonic filter power
unit, when to switch the transistors in the harmonic filter power unit, and collects data to determine
power calculations. This board also uses this data to determine shutdown conditions.

Microcomputer control panel VSD related keypad functions

Refer to 160.00-M4 for related keypad functions. Some of the displayed data in this form is different
from the 160.00-M1. Under the Options Key – the following changes will be displayed:

• VSD PHASE A INVERTER HEATSINK TEMP = °F.

• VSD PHASE B INVERTER HEATSINK TEMP = °F.
• VSD PHASE C INVERTER HEATSINK TEMP = °F.

These three temperature values are replaced with:

• VSD BASEPLATE TEMP = °F

For the low horsepower model drives. The high horsepower model drives will display three phases
of Baseplate temperature. When the Filter is present, the following data will change from:

• FILTER HEATSINK TEMP = °F.

This temperature data will now be called:

• FILTER BASEPLATE TEMP = °F.

The names for the above data were changed because the temperature sensor is now inside the
transistor module instead of the chill plate where the transistor modules are mounted. This new
sensor gives a better indication of true temperature of the power electronics.

OptiView control panel VSD functions

Refer to the specific OptiView™ Control Panel operations manual for detailed information. All of the
OSCD related information is contained under the Motor and Compressor Screens.

VSD adaptive capacity control

The YORK OSCD uses a different approach to speed reduction compared to earlier variable
speed products. There is no longer a pre-programmed surge map – the YORK® adaptive system
experiments with the speed and vanes to find the optimum speed for any given condition. It does
not always encounter a surge in the process, but when it does, the Adaptive Capacity Control (ACC)

Liquid-Cooled OptiSpeed Compressor Speed Drive 19

stores the conditions surrounding the surge into memory, so that it can avoid the stored operating
point anytime in the future.
Early versions of the ACC software required that the drive always start and run up to full speed. ACC
software starting with version C.ACC.01.04 applies anew slow ramp up of the drive speed. This new
software lowers the peak current demand from the drive during start up, saves additional energy,
and reduces the possibility of the chiller running in a stall condition.
The new software will quickly ramp the compressor speed up to 1/2 speed, and then it takes 5
minutes to ramp up to full speed. During this slow ramp up period the vanes will open to meet
the cooling demand. If the leaving chilled liquid temperature is within +0.5 or lower of the leaving
chilled liquid temperature setpoint, then the drive speed will stop increasing the RPM of the
compressor motor, and start to search for a surge map point. On extremely hot days the chiller
may surge during the slow ramp period. The new software has a method to limit the surging. If two
surges were to occur during the slow ramp period, then the speed of the drive will increase to full
speed.
Now that the ACC function is provided by the microboard in the OptiView panel future control
changes will be covered by the operation manual for the chiller model of interest. All versions of
software require two conditions to be met for speed reduction to occur. These two conditions are:
Setpoint requirements
The leaving chilled liquid temperature must be within +0.5°F or lower from the leaving chilled liquid
temperature setpoint. A programmable value is now available through the OptiView panel on
software versions C.OPT.01.21.307 for the YK chiller. This programmable value is not available on
the YT chiller. Speed reduction will not occur until the leaving chilled liquid temperature reaches
this range.
Stability requirements
The leaving chilled liquid temperature must be stable. Lack of stability will be indicative of the
vanes hunting, the leaving chilled liquid temperature varying, and the green LED on the ACC will be
on. Once the above conditions are met, the ACC may begin to lower the speed of the compressor
motor 1/10 of a hertz at a time. As the ACC lowers the speed, the leaving chilled liquid temperature
will begin to creep up. As this occurs, the control center will begin to open the vanes slightly, just
enough to maintain the leaving chilled liquid temperature within +/- 0.5°F of the leaving chilled
liquid temperature setpoint. The ACC will continue to lower speed, with the leaving chilled liquid
temperature control in turn driving the vanes to a more open position. This process will continue
until one of three following situations occur. This setting is no longer available after software
version C.OPT.01.21.307 for the YK chiller.

Full open vane operation

Once the vanes reach the full open position, the ACC knows it can no longer reduce speed and
maintain the leaving chilled liquid temperature setpoint. The ACC will maintain operation at this
point, with the vanes full open, and the speed at the last point reached when the vanes hit 100%. If
there is an increase in load while at this point, the ACC will increase speed until the vanes are closed
to 95% of open. The ACC will then be allowed to continue to reduce speed again.

Effects of surge
If in the process of reducing speed and opening vanes the compressor should surge, the ACC will
boost the speed up by 0.8 Hz. The ACC will store in memory a value that represents the ratio of
condenser pressure to evaporator pressure, the vane position, and the speed of the drive. The ratio
of condenser pressure to evaporator pressure is displayed as Delta P/P on the Control Panel.
The ACC will then know not to reduce speed this low again, if the same delta pressure, and the vane
position conditions are encounter again in the future. As the chiller encounters various conditions,
which result in surge, it will store more points, and eventually this storing of points creates a “Surge

20 Liquid-Cooled OptiSpeed Compressor Speed Drive

Map”. Surge may be detected in two ways, by monitoring the pressure differential across the
compressor, or by monitoring the compressor motor current. Either detection will light the Red
LED on the ACC, indicating a surge was detected. The chiller may surge 6 to 8 times before the ACC
can raise the speed enough to get the chiller back out of surge. Each surge is counted on the surge
counter, which may be viewed on the control center. This surge counter will always display the
total number of surges encountered by the chiller as determined by the ACC. Surging which occurs
at fixed speed will increment the surge counter as well, but only surges that occur when speed
reduction is possible are recorded in the surge map.

Drive not reducing speed

The ACC may begin the process of reducing speed, but may stop speed reduction if instability is
encountered. This is the same instability discussed as one of the two conditions which must be
met to begin reducing speed initially (See VSD adaptive capacity control for stability requirements).
Once the system again becomes unstable, no additional speed reduction can occur.
The most common causes for instability are:

• High condenser liquid temperature

• Dirty condenser tubes
• Chillers with very light loads
• Rapid changes to chilled or condenser liquid flow
• Valves on air-handler coils closing rapidly causing changes in heat-load
• Extremely short chilled liquid loop
• Parallel chiller with poor control causing temperature variations
• Parallel chiller with poor control of chilled or condenser water flows
• Incorrect evaporator refrigerant level

If an OSCD does not reduce speed at all, ensure that the system is not in manual speed control or
locked into fixed speed. Either situation will cause the chiller to maintain full speed. If the OSCD is
reducing speed, but not running as slow as you expect it should, it is likely because it is either in an
unstable condition, or running just above a mapped surge point. The chiller must achieve stability,
which is signaled by the green LED being extinguished, before speed reduction will commence.
Instability will cause the green LED to be illuminated.

Stability limit adjustment

Stability Limit Adjustment allows the system to properly function with larger amounts of
temperature instability. Consult YORK Service to make this adjustment.

Surge margin adjustment

Surge Margin Adjustment allows the Service Technician to increase the speed of the drive for all
mapped surge points. This parameter is rarely used, and it decreases the efficiency of the OSCD
chiller system.
The ACC board is no longer in production. The functions of the ACC board were transferred to the
OptiView panel in 2008 with software version C.OPT.01.19.307 and the 031-02430-xxx board.

Liquid-Cooled OptiSpeed Compressor Speed Drive 21

OptiSpeed compressor drive details
System architecture
Figure 3: OptiSpeed system architecture (Model VSD 351 without harmonic filter shown,
similar to 270, 292, 424 models)

Callout Description Callout Description

1 Cooling coil 4 Control transformer
2 Cooling fans 5 Input breaker
3 Inductor

22 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 4: OptiSpeed system architecture (Model VSD 351 without harmonic filter shown,
similar to 270, 292, 424 models)

Callout Description
1 Cooling fans
2 Cooling coil
3 Gate driver board
4 IGBT
5 DC bus isolator board
6 SCR trigger board
7 SCR/Diode module

Liquid-Cooled OptiSpeed Compressor Speed Drive 23

Figure 5: OptiSpeed system architecture (Model LVD 419 shown, similar to 385, 503, 608, 658,
704, and 900 models)

Callout Description
1 Input breaker
2 Inductor

24 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 6: OptiSpeed system architecture (Model LVD 419 shown, similar to 385, 503, 608, 658,
704, and 900 models)

Callout Description
1 Cooling coil
2 Cooling fan
3 SCR trigger board
4 SCR/Diode module
5 IGBT module
6 Gate driver board

Liquid-Cooled OptiSpeed Compressor Speed Drive 25

Figure 7: OptiSpeed system architecture (Model VSD 503 with harmonic filter shown, similar
to 385, 419, 608 models)

Callout Description
1 Filter pre-charge contactor
2 Filter supply contactor
3 Direct current current transducers (DCCTs)
4 Filter issues
5 50/60 Hz inverter (50 Hz applications only)
6 Filter inductor
7 Filter trap assembly
8 Filter pre-charge resistors

26 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 8: OptiSpeed system architecture (Model VSD 503 with harmonic filter shown, similar
to 385, 419, 608 models)

Callout Description
1 Line voltage isolation board
2 Filter power module
3 Filter power unit
4 VSD power unit

Liquid-Cooled OptiSpeed Compressor Speed Drive 27

Figure 9: OptiSpeed system architecture (Model VSD 790 shown, similar to 608, 658, and 704
models)

Callout Description Callout Description

1 Air coil 5 Line inductor
2 Filter supply contactor 6 Filter inductor
3 Filter DCCTs 7 Circuit breaker
4 Filter fuses 8 Filter trap

28 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 10: OptiSpeed system architecture (Model VSD 790 shown, similar to 608, 658, and 704
models)

Callout Description
1 Filter line voltage isolation board
2 Drive logic board
3 Filter power unit
4 Filter logic board
5 SCR trigger board
6 Service hole
7 Filter input current transformer
8 Drive power unit
9 Drive output current transformer
10 Cooling coil fan

Liquid-Cooled OptiSpeed Compressor Speed Drive 29

Figure 11: OptiSpeed system architecture (Model 1055 shown, similar to 868, 882, 914, 917,
and 948 models)

Callout Description Callout Description

1 Filter pre-charge contactor 5 Filter inductor
2 Air coil 6 Line voltage isolation board
3 Filter supply contactor 7 Circuit breaker
4 Line inductor 8 Filter trap

30 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 12: OptiSpeed system architecture (Model 1055 shown, similar to 868, 882, 914, 917,
and 948 models)

Callout Description
1 Filter power unit
2 Service hole
3 SCR trigger board
4 Drive power unit
5 Filter input current transformer

In Figure 12, the drive and filter logic boards are mounted on the right door.

Liquid-Cooled OptiSpeed Compressor Speed Drive 31

Printed circuit boards
Figure 13: VSD logic board (located on panel door)

Figure 14: SCR trigger board

32 Liquid-Cooled OptiSpeed Compressor Speed Drive

Figure 15: Optional harmonic filter logic board (located on panel door)

Figure 16: Gate driver board and power module (Model 351 shown, similar to 270, 292, 424
models)

Liquid-Cooled OptiSpeed Compressor Speed Drive 33

Safety shutdowns
General information
The Shutdowns are organized in alphabetical order based on the OptiView™ Control Center
messages. The Microcomputer Control Center messages are also included under these headings.
Whenever a Safety Shutdown is generated by the OSCD or Harmonic Filter Logic Board, a series of
events occurs.

• If the chiller is not running at the time of the shutdown, the OSCD Logic Board does not turn
on the gate drivers.
• The K1 relay on the OSCD logic board de-energizes to indicate to the Control Center that the
OSCD has shut down. The K1 relay remains de-energized until the cause of the shutdown is
corrected.
• If the chiller is running at the time of the shut- down, the Control Center starts a coastdown
period (150 seconds for centrifugal chillers or shorter for those chillers that contain the
optional Quick Start feature).
• The message “VSD Shutdown - Requesting Fault Data” is displayed when the Control Center
requests the fault data from the OSCD.
• The OSCD or Harmonic Filter Logic Board sends a shutdown code through the
communications link to the Control Center. The microboard interprets the shutdown code
and displays a shutdown message on the display of the Control Center.

After the coastdown period times out, you can restart the chiller if the shutdown is no longer
active. Place the Compressor Switch in the Stop/Reset position, and then into the Start position and
release. The chiller starts if no faults are active.

34 Liquid-Cooled OptiSpeed Compressor Speed Drive

Safety shutdown messages
Table 3: Safety shutdowns
Message Description
The OSCD logic board generates this shutdown. This shutdown will become active
Motor or Starter – Current Imbalance
when the highest of the three motor currents exceeds 80% of the programmed
MOTOR OR STARTER – CURRENT
FLA. After these conditions are met, if any one phase of motor current exceeds
IMBALANCE
30% of the average current for 45 seconds, a Safety shutdown will be activated.
The OSCD logic board generates this shutdown by reading the current from the
three output current transformers. The shutdown is generated when the OSCD
VSD - 105 % Motor Current Overload logic board has detected that the highest of the three output phase currents has
105% MOTOR CURRENT OVERLOAD exceeded 105% of the programmed 100% full load amps (FLA) value for more than
40 seconds. This shutdown requires a manual reset using the Reset pushbutton
on the OSCD logic board.
A thermistor sensor is located on the copper chill plate of the OSCD Power Unit. If
at anytime this thermistor detects a temperature of 170°F (76°C) or higher a shut-
down will occur. The cooling fans and coolant pump on the OSCD will continue to
run after the shutdown until the thermistor temperature has dropped below 160°F
(71°C), and below the reset threshold value for the inverter listed in the following
table for a given model. This shutdown requires a manual reset using the Reset
VSD - High Converter Heatsink
push-button on the OSCD logic board.
Temperature
Threshold reset
HIGH CONVERTER HEATSINK TEMP Drive model Drive horsepower rating
value
270, 292, 351, 385, 419, 424, 503, 608, 658,
LVD, VSD 704, 790, 868, 882, 900, 914, 917, 948, 170°F (77°C)
1055
LVD 546, 575, 750 175°F (79°C)
LVD 1100 222°F (105°C)
A thermistor sensor is located inside the transistor module on the OSCD power
VSD - High Inverter Baseplate unit. If at anytime this thermistor detects a temperature of 175°F (79°C) or higher
Temperature (270, 292, 351 and 424 Hp a shutdown will occur. The cooling fans and coolant pump on the OSCD will
drives) continue to run after the shutdown until the thermistor temperature has dropped
HIGH INVERTER BASEPLATE below 165°F (74°C), and the converter temperature is below 160°F (71°C). This
TEMPERATURE FLT shutdown requires a manual reset using the Reset push-button on the OSCD logic
board.
Note: The X will indicate the phase that the high temperature has occurred.

A thermistor sensor is located inside each transistor module on the OSCD power
unit. If at anytime this thermistor detects a temperature above the shutdown
threshold value listed in the following table for a given model, a shutdown occurs.
The cooling fans and coolant pump(s) on the OSCD will continue to run after the
shutdown until the temperature of the converter is less than 160°F (71°C), and the
inverter temperature is less than the reset threshold value listed in the following
table for a given model. This shutdown requires a manual reset using the Reset
VSD - High Phase (X) Inverter
push-button on the OSCD logic board.
Baseplate Temperature (on models
where 3 transistors modules are used) Drive model Threshold Threshold reset
Drive hp rating
shutdown value value
HIGH PHASE (X) BASEPLATE
TEMPERATURE FAULT 385, 419, 503, 608,
LVD, VSD 175°F (79°C)
(575 VAC)
608 (400 VAC), 658,
170°F (77°C)
704, 790, 868, 882,
LVD, VSD 196°F (91°C)
900, 914, 917, 948,
1055
LVD 546, 575 190°F (88°C)
175°F (79°C)
LVD 750 210°F (99°C)
LVD 1100 232°F (111°C) 222°F (105°C)

Liquid-Cooled OptiSpeed Compressor Speed Drive 35

Table 3: Safety shutdowns
Message Description
If the OSCD fails to meet the precharge criteria (refer to precharge faults), the
precharge circuit waits for a period of 10 seconds before another precharge
VSD - Precharge Lockout attempt. The unit’s cooling fans and coolant pump remain energized during this
PRE-CHARGE FAULT LOCKOUT time period. Following this 10-second period, the precharge is initiated again. The
unit attempts to meet the precharge criteria three consecutive times before the
OCSD shuts down, locks out, and displays this message.
A thermistor sensor is located inside the transistor module on the harmonic filter
power unit. If at anytime this thermistor detects a temperature higher then the
threshold value a shutdown will occur. See the following chart for the shutdown
Harmonic Filter - High Baseplate threshold values. A manual reset is required by pressing the “Overtemp Reset”
Temperature pushbutton located on the Filter Logic board.
HIGH FILTER BASEPLATE TEMPERATURE Drive hp rating Threshold shutdown value
FAULT 270, 292, 351 175°F (79°C)
385, 419, 424, 503, 608 (575 VAC) 190°F (88°C)
608 (400 VAC), 704, 658, 790 194°F (90°C)
868, 882, 914, 917, 948, 1055 175°F (79°C)
The control center determines this shutdown by using data supplied from the
harmonic filter logic board. This shutdown indicates that the filter is not operating
correctly or the input current to the OSCD/filter system is not sinusoidal. This
shutdown will occur if the Total Demand Distortion (TDD) in any one phase
Harmonic Filter - High Total Demand
exceeds 25% continuously for 45 seconds. TDD is defined by the IEEE Std 519-1992
Distortion
standard as “the total root - sum - square harmonic current distortion, in percent
FLTR HIGH TDD FLT
of the maximum demand load current (15 or 30 min demand)”. The harmonic
filter option was designed to provide an input current TDD level of 8% or less for
the OSCD system. A standard OSCD less the optional filter typically has an input
current TDD level on the order of 28% to 30%.

36 Liquid-Cooled OptiSpeed Compressor Speed Drive

Cycling shutdowns
General information
The Shutdowns are organized in alphabetical order based on the OptiView Control Center Panel
messages. The Microcomputer Control Panel messages are also included under these headings.
Whenever the OSCD or Harmonic Filter Logic Board generates a Cycling Shutdown, a series of
events occurs.

• If the chiller is not running at the time of the shutdown, the OSCD Logic Board does not turn
on the output transistors.
• The K1 relay on the OSCD logic board de-energizes. This action indicates to the Control
Center that the OSCD has shut down. The K1 relay remains de-energized until the cause of
the shutdown is corrected.
• If the chiller is running at the time of the shutdown, the Control Center starts a coastdown
period (150 seconds for centrifugal chillers).
• The message “VSD Shutdown - Requesting Fault Data” is displayed when the Control Center
requests the fault data from the OSCD.
• The OSCD or Harmonic Filter Logic Board sends a shutdown code to the Control Center. The
microboard interprets the shutdown code, and displays a shutdown message on the display
of the Control Center.

After the coastdown period times out, the chiller automatically restarts if the shutdown is no longer
active. Leave the Compressor Switch in the Run position. The chiller starts if no faults are active.

Cycling shutdown messages

Table 4: Cycling shutdown message
Message Description
The DC link is filtered by many large capacitors, which are rated for 450 VDC.
These capacitors are connected in series to achieve a 900 VDC capability for the
VSD - DC Bus Voltage Imbalance DC link. It is important that the voltage is shared equally between the two sets of
BUS VOLTAGE IMBALANCE FAULT series capacitors. Each set of capacitors must share approximately 1/2 of the total
DC link voltage. If the difference in the voltage between the two sets of capacitors
is greater than ± 88 VDC then this shutdown will occur.
The DC bus voltage is continuously monitored and a shutdown will occur if the DC
VSD - High DC Bus Voltage bus voltage exceeds 745 VDC (for 400 VAC and 460 VAC units) or 909 VDC (for 575
BUS OVER-VOLTAGE FAULT VAC units). This shutdown will protect the capacitors from a voltage that exceeds
their rating.
The ambient temperature of the OSCD is monitored by a temperature sensor
VSD - High Internal Ambient
mounted on the OSCD logic board. The high ambient trip threshold is 145°F (63°C)
Temperature
for all models. If this fault occurs, the fans and coolant pump will remain on until
HIGH AMBIENT TEMPERATURE FLT
the internal ambient temperature has fallen to 137°F (58°C).

Liquid-Cooled OptiSpeed Compressor Speed Drive 37

Table 4: Cycling shutdown message
Message Description
This shutdown is generated by the OSCD logic board. If any one phase of motor
current as measured by the Output Current Transformers exceeds a threshold.
Refer to the chart below for the shutdown threshold value.
Drive hp rating Threshold shutdown value
270, 292, 351, 424 771 Amps Peak
385, 419, 503, 608 1200 Amps Peak
VSD - High Phase A (or B, C)
Instantaneous Current 546, 575, 608 (400 VAC), 658, 704, 750 790 1890 Amps Peak
900, 914, 917, 948, 1055, 1100 2749 Amps Peak
PHASE A (OR B, C) OVERCURRENT
FAULT If an Instantaneous Current Fault occurs but the chiller restarts and runs without a
problem, the cause may be attributed to a voltage sag on the utility power feeding
the OSCD that is in excess of the specified dip voltage rating for this product. This
is especially true if the chiller was running at, or near, full load. If there is a sudden
dip in line voltage, the current to the motor will increase. The chiller vanes cannot
close quickly enough to correct for this sudden increase in current and the chiller
will trip on this fault.
At power-up, the OSCD logic board will go through a process called initialization.
VSD - Initialization Failed At this time, memory locations are cleared, jumper positions are checked, and
VSD INITIALIZATION FAILED communications links are established between the OSCD logic board, and the
Control Center.
The J1 connector on the OSCD logic board contains jumpers along with wires from
the output CTs. The jumpers configure the OSCD logic board to the HP rating of
VSD - Invalid Current Scale Selection the OSCD being used in this application in order to properly scale the output cur-
INVALID CURRENT SCALE FAULT rent. If the jumper configuration is found by the logic board to be invalid, the
system will be shut down and the above message will be generated. The proper
jumper configuration is shown on the wiring label for the OSCD.
This shutdown is generated by the OSCD logic board, and it indicates that one of
the low voltage power supplies for the OSCD logic board has dropped below their
VSD - Logic Board Power Supply
allowable operating limits. The power supplies for the logic boards are derived
MAIN BOARD POWER SUPPLY
from the secondary of the 120 VAC to 24 VAC transformer which in turn is derived
from the 480 VAC to 120 VAC control transformer.
This shutdown is generated by the OSCD logic board. If a communications
VSD - Logic Board Processor
problem occurs between the two microprocessors on the OSCD logic board this
PWM COMMUNICATIONS FAULT
shutdown will occur.
VSD - Low Converter Heatsink A thermistor sensor is located on the SCR/Diode block side of the copper chill
Temperature plate on the OSCD Power Unit. Anytime this thermistor detects a temperature of
LOW CONV HEATSINK TEMP. 37°F (3°C) or lower a shutdown will occur.
If the line voltage were to quickly drop the current seen by the motor could exceed
it’s rating. The low bus voltage shutdown will prevent this from happening. The
VSD - Low DC Bus Voltage
shutdown is generated when the DC link voltage drops below 500 VDC for 460 VAC
LOW DC BUS VOLTAGE FLT
input voltage, 414 VDC for 380, 400, and 415 VAC input voltage or 600 VDC for 575
VAC input voltage.
VSD - Low Inverter Baseplate A thermistor sensor is located inside the transistor module(s) on the OSCD power
Temperature unit. Any time this thermistor detects a temperature of 37°F (3°C) or lower a shut-
LOW INVERTER BASEPLATE down will occur. The displayed message will change to LOW INVERTER PHASE (A,
TEMPERATURE FLT B, or C) when more than one transistor module is used in the power assembly.
A second level of overcurrent current protection exists on the OSCD gate driver
board. The collector-to-emitter voltage of each transistor module is checked while
VSD - Phase A (or B, C) Gate Driver the device is turned on. This is called the collector-to-emitter saturation voltage.
PHASE A (B, C) GATE DRIVER FLT If the voltage across the transistor module is greater than a set threshold, the
transistor module is turned off. This fault can also be caused if the transistor is not
being turned on when it should.
VSD - Precharge - DC Bus Voltage The definition for this fault is identical to “VSD - DC Bus Voltage Imbalance” except
Imbalance that the fault has occurred during the precharge period, which begins during pre-
PRECHARGE BUS V IMBALANCE lube. Refer to “ VSD - DC Bus Voltage Imbalance” shutdown for more details.

38 Liquid-Cooled OptiSpeed Compressor Speed Drive

Table 4: Cycling shutdown message
Message Description
This fault has two different timing events. First, the DC Bus voltage must be equal
to or greater than 50 VDC for 460 VAC input voltage, 41 VDC for 380, 400 and 415
VSD - Precharge - Low DC Bus Voltage VAC input voltage, or 60 VDC for 575 VAC input voltage, 4 seconds after pre-charge
PRECHARGE LOW VOLTAGE FAULT has begun. Second, the DC Bus voltage must be equal to or greater than 500 VDC
for 460 VAC input voltage, 414 VDC for 380, 400 and 415 VAC input voltage or 600
VDC for 575 VAC input voltage, 20 seconds after pre-charge has begun.
Two run signals are generated by the Control Center, one via hardware and the
second via the communications link. Upon receipt of either of the two run signals
VSD - Run Signal
by the OSCD logic board, a 5-second timer will begin. If the missing run signal is
RUN RELAY FAULT
not received within the 5-second window the OSCD logic board will shut down and
the Control Center will display the shutdown message.
This message is generated when communications between the microboard
and the ACC board, or the ACC board and OSCD logic board is disrupted for a
VSD - Serial Communications least 22 seconds. If the optional Harmonic Filter is installed then the fault can
SERIAL RECEIVE FAULT be generated when the communications between the OSCD logic board and the
Harmonic Filter logic board, or the Harmonic Filter logic board and the ACC board
is disrupted.
This shutdown is generated by the SCR Trigger board and relayed to the OSCD
logic board to initiate a system shutdown. The single phase control uses circuitry
to detect the loss of any one of the three input phases. The trigger board will
detect the loss of a phase within one half line cycle of the phase loss. An LED
VSD - Single Phase Input Power
on the SCR Trigger board will indicate that the board is detecting the fault, and
SINGLE PHASE POWER SUPPLY
not a wiring problem between the trigger board and the OSCD logic board. This
message is also displayed every time power to the OSCD is restored, or if the input
power dips to a very low level. Usually it indicates that someone has opened the
circuit breaker.
Whenever the OSCD initiates a fault, it first opens the fault relay on the OSCD logic
board. When the relay opens a message is sent to the ACC board, detailing the
VSD - Stop Contacts Open cause of the fault. If this circuit ever opens without receiving an accompanying
INVERTER INITIATED STOP FAULT cause for the fault over the communication link (within 11 communication tries,
ap- proximately 22 seconds) this message will be displayed. This fault may be
replaced with a Serial Communications fault if the serial link has failed.
The three phases of RMS filter current are measured by the output DCCTs’. This
information is sent to the harmonic filter logic board. If any one phase of filter cur-
rent exceeds a threshold for 40 seconds a shutdown will occur. Refer to the chart
below for the shutdown threshold value.
Harmonic Filter - 110 % Input Current Drive hp rating Threshold shutdown value
Overload 270, 292, 351 128 Amps
FLTR OVERLOAD FLT 424 138 Amps
385, 419, 503 176 Amps
608 (575 VAC) 190 Amps
608 (400 VAC), 658, 704, 790 278 Amps
868, 882, 914, 917, 948, 1055 385 Amps
The DC link is filtered by many large capacitors. These capacitors are connected
in series to achieve a higher DC link voltage then can be supported by a signal
capacitor. It is important that the voltage is shared equally between the two sets
Harmonic Filter - DC Bus Voltage of series capacitors. Each set of capacitors must share approximately 1/2 of the
Imbalance total DC link voltage. The harmonic filter logic board then measures the voltage of
FLTR BUS V IMBALANCE FLT the 2 sets of the bus capacitors. If at anytime while the harmonic filter is running
that the difference in the voltage between the 2 sets of capacitors is greater
than 50 VDC (for 380 through 460 VAC input voltage) 65 VDC (for 575 VAC input
voltage), then a shutdown will occur.

Liquid-Cooled OptiSpeed Compressor Speed Drive 39

Table 4: Cycling shutdown message
Message Description
During initialization, with no current flowing through the Direct Current Current
Harmonic Filter - DC Current Transducers (DCCTs), the DCCT’s output voltages are measured and compared
Transformer 1 (or 2) with a preset limit in the harmonic filter logic board. If the measured values
FILTER DCCT 1 (OR 2) ERROR exceed the preset limits, the DCCTs are presumed to be bad and this shutdown
will be generated.
The harmonic filter logic board continuously monitors the harmonic filter DC link
voltage if the level of the DC link voltage exceeds a range of 822 to 900 VDC (for
Harmonic Filter - High DC Bus Voltage 380 through 460 VAC input voltage) or 999 to 1099 VDC (for 575 VAC input voltage)
FLTR BUS OVER-VOLTAGE FLT this shutdown is initiated. Keep in mind that the harmonic filter has its own DC
Link as part of the harmonic filter power unit. The harmonic filter DC Link is not
connected in any way with the drive’s DC Link.
The output current of the harmonic filter is read by the Direct Current-Current
Transducer (DCCT). This current information is sent to the harmonic filter logic
board where it is compared against a threshold. If the output current of the
harmonic filter power unit is greater than the threshold, then the harmonic filter
will turn off for 5-6 line cycles. After that time the filter operation will resume. If
Harmonic Filter - High Phase A (or B, the harmonic filter operation is stopped 3 times within a period of 60 line cycles,
C) Current then the filter and VSD power units are shut down and this message is generated.
FLTR PHASE A (B, C) OVERCURRENT Drive hp rating Threshold shutdown value
270, 292, 351, 424 378 Amps Peak
385, 419, 503, 608 (575 VAC) 523 Amps Peak
608 (400 VAC), 658, 704, 790 781 Amps Peak
868, 882, 914, 917, 948, 1055 1225 Amps Peak
This shutdown states that the hardware on the harmonic filter logic board is
Harmonic Filter Communications indicating a fault, but the software on the harmonic filter logic board does not
IEEE-519 FILTER FAULT state why. The harmonic filter logic board signals a fault condition to the OSCD
logic board but does not respond to a software request for fault information.
This shutdown indicates that one of the low voltage power supplies on the
Harmonic Filter - Logic Board Power harmonic filter logic board have dropped below their permissible operating
Supply voltage range. The harmonic filter logic board receives its power from the OSCD
FLTR POWER SUPPLY FLT logic board. The power supplies for the OSCD logic board are in turn derived from
the secondary of the 120 VAC to 24 VAC transformer.
The harmonic filter dynamically generates its own filter DC link voltage by the
interaction of the harmonic filter inductor and switching its transistors. This DC
level is actually higher than the level obtained by simply rectifying the input line
voltage.
Note: The DC link voltage is always higher on the harmonic filter power unit
then on the OSCD VSD power unit.
Harmonic Filter - Low DC Bus Voltage
Thus the harmonic filter actually performs a voltage “boost” function. This is
FLTR LOW BUS VOLTAGE FLT
necessary in order to permit current to flow into the AC line from the harmonic
filter when the AC line is at its peak level. This particular shutdown and its
accompanying message are generated when the harmonic filter’s DC link voltage
drops to a level less than 80 VDC (for 380 through 460 VAC input voltage), 110 VDC
(for 424 HP) and 140 VDC (for 575 VAC input voltage 608 HP) below the harmonic
filter DC link voltage setpoint.
This shutdown indicates that a circuit called a “phase locked loop” on the
Harmonic Filter - Phase Locked Loop
harmonic filter logic board has lost synchronization with the incoming power line
FLTR PHASE LOCK LOOP FLT
for a period of time.

40 Liquid-Cooled OptiSpeed Compressor Speed Drive

Table 4: Cycling shutdown message
Message Description
Two minimum voltage thresholds must be met in order to complete the precharge
cycle. The first occurs 1/10th of a second after pre-charge is initiated and the other
Harmonic Filter - Precharge - Low DC occurs 5 seconds after precharge is initiated. See table below for specific values.
Bus Voltage Nominal input voltage 1st minimum voltage 2nd minimum voltage
FLTR PCHARGE LOW BUS V FLT value value value
380-460 VAC 41 VDC 425 VDC
575 VAC 60 VDC 630 VDC
When a digital run command is received at the harmonic filter logic board from
Harmonic Filter - Run Signal the OSCD logic board, a 1/10 second timer is started. A redundant run command
FLTR RUN RELAY FLT must also occur on the communication link from the OSCD logic board before the
timer expires or the OSCD will be shut down.

Liquid-Cooled OptiSpeed Compressor Speed Drive 41

Warning messages
General information
A WARNING message indicates that the operation of the OSCD or the Harmonic Filter is affected in
some manner, but the OSCD is still functioning.

Warning messages
Table 5: Warning messages
Warning Description
This message is displayed when the Pre-Rotation Vanes are not calibrated or have
Warning - Vanes Uncalibrated - Fixed failed to calibrate, and the OSCD is enabled. Under this condition the OSCD will
Speed run at a constant maximum speed. This message will no longer appear after a
successful calibration.
This message is displayed if the communications link between the OSCD logic, and
the harmonic filter logic, or the ACC boards are interrupted for at least a period
Warning - Harmonic Filter - Data Loss of 20 seconds. This message can also occur as a background message when the
FILTER - DATA LOSS chiller is running. When this message is displayed all harmonic filter related values
are replaced with Xs. If communications is re-established, the mes- sage will
disappear, and normal values will again be displayed.
This message is displayed when the function of the Harmonic Filter is inhibited
Warning - Harmonic Filter - Operation
at the Control Center. This message is no longer displayed when the function of
Inhibited
the Harmonic Filter is enabled at the Control Center. The function of the harmonic
FILTER - OPERATION INHIBITED
filter can only be inhibited or turned on when the chiller is not running.

42 Liquid-Cooled OptiSpeed Compressor Speed Drive

VSD frequently asked questions
Why doesn’t the measured input amps of the OSCD agree with the rated FLA?
The input current to the OSCD may be considerably lower, compared to the output current. This is
due to the power factor at the input to the OSCD being greater than 0.95, and nearly unity when
the Harmonic Filter option is included. Chiller FLA must be measured at the motor terminals, where
the power factor is the normal motor power factor. Use a true RMS reading meter to make these
measurements.
Is a Condenser Water Strainer used with the shell and tube heat exchanger?
Since the shell and tube heat exchanger can be cleaned with a rifle brush, no extra precautions are
needed to keep the heat exchanger cleaned. No strainer is provided with this OSCD. The intent is to
have the heat exchanger cleaned annually. Gaskets are available (refer to the service parts list).
What is the timing of the Anti-Recycle when an OSCD is applied?
The anti-recycle time is much quicker with an OSCD than with a starter. The reason is the
elimination of inrush current on start-up. The OptiSpeed compressor drive slowly accelerates the
compressor motor so that the motor does not consume more than 100% of the motor’s nameplate
full load amps. The anti-recycle time is five starts in succession, followed by a ten minute wait. After
ten minutes, the OSCD can be started five more successive starts. This is permitted on OSCD units
only, due to the low current draw and reduced motor heating during startup.
Should the customer install isolation between the Power Conduits and the OptiSpeed
Compressor Drive?
We no longer require a section of non-metallic conduit at the entrance and exit of the OSCD as we
did on previous products. If any customer or installer wishes to continue to follow this practice, we
have no objections as long as the OSCD is properly grounded.
When is a Booster Pump required on a Retrofit OptiSpeed Compressor Drive?
Detailed information is supplied in Form160.05-N4. In general, the OSCD requires 8 ft of head for
proper water flow to the OSCD heat exchanger. If this amount of head is not available, then a
booster pump is required.
Can I apply an OptiSpeed Compressor Drive to a generator?
Yes, the OSCD can be applied to a generator. No modifications are required for a generator
application. We have several OSCD installations running on generator power without difficulty. It
is necessary that the generator’s output voltage and frequency be maintained within the specified
range for that particular OSCD. This is usually not a problem for most generators, since motor
current at startup is limited to less than 1X the Full Load Amps (FLA).
My chiller will not slow down, why?
The OSCD will not reduce the motor speed until the leaving chilled water temperature is below 0.5
degree from setpoint. Once in this window, the speed still cannot be reduced until the operation
is deemed to be stable, based upon the vanes are not continually moving open and closed to
maintain temperature. This hunting effect is normally due to one of the following:

• Chilled water and Condenser water flows are not at design GPMs. The rate of change in flow
maybe too fast for the chiller to be determined as stable.
• Return water temperature is varying due to 3-way valves or other system configuration, and
the chiller is simply following changes in load.

Liquid-Cooled OptiSpeed Compressor Speed Drive 43

 • Vane stroke is too large. Remove the sensitivity jumper in the Micro Computer Control Center,
or program a lower sensitivity on the OptiView Control Center. Also, check the vane motor
to see that the fullest possible stroke is being used. Moving the vane motor arm pivot point
closer to center, and extending the degrees of travel by adjusting the internal end stops, will
reduce the amount of vane action for the same period of operation.
• Verify that the condenser is clean.
• Verify that the liquid level control is working properly, and maintaining a refrigerant level in
the condenser.
• Ensure that the condenser water temperature is proper for the load on the chiller. In many
cases, the condenser water temperature is still at 85°F.

Failure to reduce speed may also be due to the system having been placed in Manual Speed when
in VSD Service Mode.
Do I have a problem with my coolant? The pink color is no longer visible?
The coolant normally has a pink or rose color when new. After several months of operation, this
color may dissipate, and the coolant may appear almost colorless. The lack of the color in the
coolant does not necessarily indicate a problem. Most colorless samples test above 1000 PPM
nitrite, which is normal. There is no need to flush the system unless you find the coolant becoming
opaque or cloudy. In this case we suggest you obtain a sample for analysis, then flush the system
with coolant and install fresh coolant. The coolant must be changed every year regardless of color
or test results. The coolant is required to be changed every year.

44 Liquid-Cooled OptiSpeed Compressor Speed Drive

Unit conversion
The following factors can be used to convert from English to the most common SI metric values.
Table 6: SI metric conversion
Measurement Multiply English unit By factor To obtain metric unit
Capacity Tons Refrigerant Effect (ton) 3.516 Kilowatts (kW)
Power Horsepower 0.7457 Kilowatts (kW)
Flow Rate Gallons / Minute (gpm) 0.0631 Liters / Second (L/s)
Feet (ft) 0.3048 Meters (m)
Length
Inches (in.) 25.4 Millimeters (mm)
Weight Pounds (lb) 0.4536 Kilograms (kg)
Velocity Feet / Second (fps) 0.3048 Meters / Second (m/s)
Feet of Water (ft) 2.989 Kilopascals (kPa)
Pressure Drop
Pounds / Square Inch (psi) 6.895 Kilopascals (kPa)

Temperature
To convert degrees Fahrenheit (°F) to degrees Celsius (°C), subtract 32° and multiply by 5/9 or
0.5556.
Example: (45.0°F - 32°) x 0.5556 = 7.22°C
To convert a temperature range (i.e., a range of 10°F) from Fahrenheit to Celsius, multiply by 5/9 or
0.5556.
Example: 10.0°F range x 0.5556 = 5.6°C range

Liquid-Cooled OptiSpeed Compressor Speed Drive 45

© 2020 Johnson Controls. 5000 Renaissance Drive, New Freedom, York, PA 17349, USA. Subject to change without notice. All
rights reserved.