Pressure

Differential pressure switch

Models 306, 386
WIKA data sheet PV 35.63

Applications
■ Power generation
■ Waste water management
■ Oil and gas
■ Petrochemical industries

Special features
■ Internal Switch point adjustment for critical applications
■ Stainless steel case option for corrosive environment
■ Switch point repeatability of ±1% of FSR for reliable
switching
■ Two set-point option for controlling at different process
levels

Fig. Left: Differential pressure switch, flameproof

Right: Differential pressure switch, weatherproof

Description

The model 306 differential pressure switch has been Adjustable switch differential combinations are available to
designed for control and monitoring applications. realize flexible on/off controls. This wide setting range is often
The stainless steel case option enables the pressure switch needed for the on/off control mode of cyclic applications.
to perform in harsh operating conditions of the process
industry. The switch point can be specified on site, with internal
adjustment options. Depending on the application, the
The switch point repeatability to ±1% enables reliable appropriate variant for the contact version and the electrical
switching in critical operating conditions. Low pressure connection can be selected. For example, hermetically
ranges with diaphragm sensor elements enable to meet sealed micro switches are suitable for corrosive ambient
a variety of applications in oil, gas, power, steel and conditions.
petrochemical industries.

WIKA Data sheet PV 35.63 ∙ 06/2023 Page 1 of 9

Specifications

Basic information

Switch enclosure ■ GM style aluminium pressure die cast, weatherproof to IP66

■ GA style CF8 (304 SS) casting, weatherproof to IP66
■ GA6 style CF8M (316 SS) casting, weatherproof to IP66
■ GK style (Type-1) aluminium pressure die cast, weatherproof and
flameproof to group IIC as per IS/IEC 60079-1
■ GR style (Type-1) aluminium pressure die cast, weatherproof to
IP66 and flameproof to group IIC

Measuring element Buna-N diaphragm

Wetted parts ■ Aluminium (standard)

■ 304 SS (optional for model 306)
■ 316 SS (optional for model 306)

Output signal

Ranges Several standard ranges between (-)0.6 mbar ... 4 bar

Switching differential Fixed

Refer table 2, 3 & 4

Repeatability of the setpoint (note 3) ±1% of FSR, except range code W188.
±2% of FSR for range code W188

Maximum working pressure Refer table-4

Response time <1 second

Scale accuracy (note 6) ±5% of FSR

Switching element (notes 9 & 10) Instrument quality SPDT microswitch (Notes 10 & 11)

Operating condition

Permissible ambient temperature –25°C ... +60°C

110°C. For higher temperatures use longer impulse lines. Ask for
Maximum process temperature (note 15)
piping nomogram #441184-4

Ingress protection IP66

Process connection 1/4" NPT(F) per ASME B1.20.1 standard

Other connections through adaptor

Electrical connection 1/2" NPT(F) per ASME B1.20.1 single entry standard
Dual entry on request

Mounting Back panel / wall / Field.

Vertical position only

Page 2 of 9 WIKA Data sheet PV 35.63 ∙ 06/2023

Ordering matrix
Sample model number GM 306 B 5    P C 
--- --- --- --- --- --- --- --- --- ---
Switch enclosure
GM style aluminium pressure die cast, weatherproof to IP66––––––––––––––––––GM
GA style CF8 (304 SS) casting, weatherproof to IP66 –––––––––––––––––––––––– GA
GA6 style CF8M (316 SS) casting, weatherproof to IP66–––––––––––––––––––– GA6
GK style (Type-1) aluminium pressure die cast, weatherproof and
flameproof to Gr.IIC as per IS/IEC 60079-1–––––––––––––––––––––––––––––––––– GK
GR style (Type-1) aluminium pressure die cast, weatherproof to
IP66 and flameproof to group IIC as per IS/IEC 60079-1–––––––––––––––––––––– GR
Model
Basic differential pressure switch having fixed non-adjustable
switching differential actuated by a non-metallic diaphragm–––––––––––––––––––––––– 306
A variant of series 306, employs twin levers each operating a
SPDT microswitch actuated by a single sensor through a unique linkage
thereby providing two independent adjustable setpoints, each with its own
setting scale, spring and switch. Minimum separation between setpoints
must be more than sum of on-off differentials or 10% of FSR
whichever is higher. (Not available with GR enclosure)–––––––––––––––––––––––––––– 386
Sensor material
Buna-N diaphragm––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– B
EPDM (available only in range code W161, W162, W163 & W188)–––––––––––––––––––––––– E
Wetted part
Aluminium––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 5
304 SS–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 4
316 SS–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 2
Range code
Refer table-1 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Switch code and rating
Refer table-5 –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Electrical entry code
Refer table-6 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 
Mounting type
Panel––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– P
Wall–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– W
2" pipe––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 2
Universal––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– U
Mounting material
Mild steel–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– C
316 SS–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 2
Maximum working pressure
Refer table-7–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 

The below "Options" are available, consult sales

■ Ammonia service (EPDM ‘O’ ring mandatory)
■ Blow out disc
■ Seal ‘O’ ring – EPDM (MWT 130°C, not available in Buna-N diaphragm)
■ Optional scale accuracy ±2% (not available in GR)

WIKA Data sheet PV 35.63 ∙ 06/2023 Page 3 of 9

Table 1: Range code and availability

Range code Range 306 386

M009 § (-)2.5 ... 2.5 mbar P Í

M012 § 0 ... 5 mbar P Í
M040 3 ... 25 mbar P Í
M042 5 to 120 mbar P P
M048 50 ... 350 mbar P P
B023 0.1 ... 1.5 bar P P
B028 / K051 0.2 ... 4 bar / Kg/Cm² P P
W161 Ø (-)30 ... 150 mmWC P Í
W162 Ø (-)120 ... 120 mmWC P Í
W163 Ø (-)40 ... 10 mmWC P Í
W188 §§ (-)30 ... 250 mmWC Í P

Ø Available only with 304SS / 306SS wetted parts with ‘D’ and ‘DD’ code micro switches in GM / GA enclosures only.
§ W058 is equivalent range code for range ±25 mmWC
W069 is equivalent range code for range 0 to 50 mmWC
§§ Available in GM, GA enclosure only

Table 2: Switching differential for models 306 / 386 – GM / GA enclosures

On-off differential in mbar

Range Fixed
Range
Code Models 306 Model 386
3 D 5 9/G D/3
M009 (-)2.5 ... 2.5 mbar 0.8 0.9 1.5 - -

M012 0 ... 5 mbar 0.4 0.6 1.4 1.0 -

M040 3 ... 25 mbar 0.8 ØØ ØØ ØØ -

M042 5 to 120 mbar 12 12 12 30 30

M048 50 ... 350 mbar 20 20 25 45 60

B023 0.1 ... 1.5 bar 70 70 90 135 150

B028 / K051 0.2 ... 4 bar / Kg/Cm² 250 300 600 675 500

W161 (-)30 ... 150 mmWC - 1 - - -

W162 (-)120 ... 120 mmWC - 1 - - -

W163 (-)40 ... 10 mmWC - 1.2 - - -

W188 (-)30 ... 250 mmWC - - - - 1

˜ Multiply values in Table-2 by 1.3 for DPDT (2 × SPDT) switching.

ÛÛ For on-off differential values please consult factory.

Page 4 of 9 WIKA Data sheet PV 35.63 ∙ 06/2023

Table 3: Switching differential for models 306 / 386 – GK enclosures

On-off differential in mbar

Range Fixed
Range
Code Models 306 Model 386
3 D 5 9/G D/3
M009 (-)2.5 ... 2.5 mbar 1.4 1.6 2.5 - -

M012 0 ... 5 mbar 0.8 1.0 2.4 1.7 -

M040 3 ... 25 mbar 1.0 ØØ ØØ ØØ -

M042 5 to 120 mbar 20 20 16 50 40

M048 50 ... 350 mbar 35 35 40 75 85

B023 0.1 ... 1.5 bar 120 120 150 230 240

B028 / K051 0.2 ... 4 bar / Kg/Cm² 425 500 800 1145 680

˜ Multiply values in Table-3 by 1.2 for DPDT (2 × SPDT) switching.

ÛÛ For on-off differential values please consult factory.

Table 4: Switching differential for models 306 – GR enclosures

On-off differential in mbar

Range Fixed
Range
Code Models 306
3/D 5 9/G
M009 (-)2.5 ... 2.5 mbar 0.7 2.0 -

M012 0 ... 5 mbar 1.0 ØØ ØØ

M040 3 ... 25 mbar 16 35 35

M042 5 to 120 mbar 25 35 60

M048 50 ... 350 mbar 100 130 190

B023 0.1 ... 1.5 bar 375 700 1000

˜ Multiply values in Table-4 by 1.3 for DPDT (2 × SPDT) switching.

ÛÛ For on-off differential values please consult factory.

WIKA Data sheet PV 35.63 ∙ 06/2023 Page 5 of 9

Table 5: Switch code, rating and availability (note 10)

Switch code DC rating in Ampere Availability

Contact version AC rating Resistive Inductive in models
SPDT DPDT
250V 125V 30V 250V 125V 30V SPDT DPDT
D DD General purpose 15A 250 / 125V 0.2 0.4 2.0 0.02 0.03 1.0 306 & 386 306

3 33 General purpose 15A 250 / 125V - - - - - - 306 & 386 306

General purpose with

5 55 5A 250 / 125V 0.2 0.4 4.0 0.2 0.4 3.0 306 306
good DC rating.

Hermetically sealed,
1A 115V
9 99 inert gas filled with - - 3.0 × - - 1.0 × 306 306
400 Hz.
Silver alloy contact.

Hermetically sealed,
G GG inert gas filled with - - - 1.0 × - - 0.25 × 306 306
Gold plated contact.

Note : × For Codes 9, 99, G, GG; DC Rating of Resitive and Inductive is 28V

Table 6: Electrical entry

Single entry Dual entry

Size Ø
GM / GA GK/GR GM / GA GK/GR
1/2" NPT(F) per ASME B1.20.1 A A N N

3/4" NPT(F) per ASME B1.20.1

L - O -
through adaptor

M20 × 1.5 per ISO724 ØØ E E EB EB

7 pin plug through connector ØØØ C - - -

9 pin plug through connector D - - -

Ø Cable gland available on request

ØØ Possible in GK and GR enclosure as direct. Others through adaptor.
ØØØ Possible only in GM enclosure.

Table 7: Maximum working pressure

Range codes Wetted parts Maximum working pressure (in bar)

M009, M012, M040 Aluminium 1

M042, M048, B023, B028 Aluminium 15

M009, M012, M040, M042, M048, B023, B028 304 / 316 SS 15

W161, W188 304 / 316 SS 15

W162, W163 304 / 316 SS 7

Page 6 of 9 WIKA Data sheet PV 35.63 ∙ 06/2023

NOTES

1. Style GM/GA is weatherproof only if all entries and joint 10. Contact life of microswitches are 5 × 105 switching cycles
faces are properly sealed. Style GK / GR is weatherproof for nominal load. To quench DC sparks, use diode in
only if cover ‘O’ ring is retained in position and flameproof parallel with inductance, ensuring polarity. A ‘R–C’ network
only if proper FLP cable gland is used. It is recommended is also recommended with ‘R’ value in Ohms equal to coil
to procure cable glands along with GK / GR instruments resistance and ‘C’ value in micro Farads equal to holding
to avoid neglect of it while installation. current in Amps.

2. Intrinsic Safety (Exi) — Differrential pressure switches are 11. Model 301 can be supplied with Nitrile diaphragm for
classified as simple apparatus as they neither generate applications where pressure reversal is envisaged.
nor store energy. Hence differential pressure switches in
weatherproof (GM/ GA) enclosures also may be used in 12. All differential pressure switches are calibrated by applying
intrinsically safe systems without certification provided the pressure to HI port, venting LO port to atmosphere.
power source is certified IS. Because of the low voltages Inspection will also be limited to such a practice..
and currents it is recommended to use gold contact and
13. Ambient temperature range: All models are suitable
/ or sealed contacts.
for operating within a range of ambient temperature
3. Accuracy & Repeatability are not different for all blind from (-) 25°C to (+) 60°C provided the process does not
differential pressure switches. A shift of ±2% may be freeze within this range. Below 0°C, precautions should
observed in setpoint when pressure falls from full static be taken in humid atmospheres to prevent frost formation
pressure. Settings will also shift with varying temperature. inside the instrument from jamming the mechanism.
Occasional excursions beyond this range are possible
4. The instrument is calibrated in the mounting position but accuracy might be impaired. The microswitch is
depicted in the drawing. Mounting in any other direction the limiting factor which should never exceed the limits
will cause a minor range shift, especially in low and (-) 50°C to (+) 80°C.
compound ranges. Ranges above 1 bar will not experience
this shift. 14. Fluid Temperature: A differential pressure switch when
connected to the process is not subjected to through flow
5. A differential pressure switch is a switching device and and therefore is not fully exposed to the fluid temperature.
not a measuring instrument — eventhough it has a scale Use of adequate length of impulse piping will greatly
with ±5% FSR accuracy to assist setting. For this reason, reduce excessive heating of the sensing element. For
Test Certificates will not contain individual ON-OFF e.g., connection of 7.5 cm of 12 mm dia impulse piping will
switching values at different scale readings. Maximum reduce water temperature of 100°C to 65°C at an ambient
differential obtained alone will be declared, besides other temperature of 50°C. Ask factory for piping nomogram
specifications. #441184–4 for different temperatures.

6. Select working range of the instrument such that the set 15. Ensure that impulse pipework applies no stress on sensing
value lies in the mid 35% of the range i.e., between 35% element housing and use spanners to hold pressure port/
and 70% of range span. housing when connections are made.

7. For switching differential values refer differential tables. 16. Custom built instruments are available for special service
Switching differentials furnished are nominal values requirements under Special Engineering Category.
under test conditions at mid-scale and will vary with range
settings and operating conditions. 17. For less rigorous applications models 306 / 386 with
Nitrile diaphragm & Aluminium wetted parts are available
8. On and off settings should not exceed the upper or lower at lesser cost.
range value.
18. Accuracy figures are exclusive of test equipment tolerance
9. DPDT action is achieved by two SPDT switches on the claimed values.
synchronised to practical limits i.e., ±2% of FSR.
(Synchronisation is applicable at Setpoint only. Not 19. All performance data are guaranteed to ±5%.
applicable at Reset points.) Deadband for DPDT contacts
are higher than that of SPDT as force required to actuate
the contacts are more. Please refer respective range table
for exact values.

WIKA Data sheet PV 35.63 ∙ 06/2023 Page 7 of 9

Dimensions in mm

Range Codes : M042, M048, B023 & B028

GM enclosure GK enclosure

Surface / wall / pipe mounting Pipe mounting

Range Codes : M009, M012 & M040

SS / Aluminium diaphragm

GM enclosure GK enclosure

2" Pipe mounting details

Notes:
Pipe mounting bracket can be used for
surface / wall mounting also.
Use 2× 3/8" × 25 long screws and nuts for
surface mounting or coach screws for wall
mounting instead of ‘U’ bolts and nuts.

Page 8 of 9 WIKA Data sheet PV 35.63 ∙ 06/2023

Dimensions in mm

GR enclosure
Range Codes: M042, M048, B023, B028

Range Codes: M012, M040 – SS / Aluminium housing

2" Pipe mounting detail

Ordering information
Switch enclosure / Model / Sensor material / Wetted part / Range code / Switch code and rating / Electrical entry code /
Mounting type / Mounting material / Maximum working pressure

© 2022 WIKA Alexander Wiegand SE & Co. KG, all rights reserved.
The specifications given in this document represent the state of engineering at the time of publishing.
We reserve the right to make modifications to the specifications and materials.

WIKA Data sheet PV 35.63 ∙ 06/2023 Page 9 of 9

WIKA Instruments India Pvt. Ltd.

128 SIDCO North Phase
Ambattur Industrial Estate, Chennai 600 098
Tel. +91 44 2625 2017 / 2018 / 9840919318
switch.sales@wika.com
www.wika.co.in