user manual
cooling tower Motor
I N STA L L AT I O N - O P E R AT I O N - M A I N T E N A N C E
Z0239042_A ISSUED 06/2016 READ AND UNDERSTAND THIS MANUAL PRIOR TO OPERATING OR SERVICING THIS PRODUCT
installation
RECEIVING AND STORING MOTORS INSTALLATION
A motor should be inspected on receipt to make sure it was Check to see that the motor nameplate data agrees with
not damaged during shipment. Turn the shaft by hand to the voltage and frequency of the power supply provided
see that it turns freely. Check motor nameplate for correct for the motor. All induction motors will operate successfully
horsepower, voltage, phase and speed. when the frequency is not more than five percent above or
If a motor is stored before installation, place it in a building below the nameplate rating, the voltage is not more than
in which air is kept reasonably dry and with a minimum of ten percent above or below the nameplate rating, and the
temperature fluctuation to prevent moisture condensing in combined variation in voltage and frequency is not more than
the motor. Do not store directly on the floor, always block up. ten percent above or below the nameplate rating.
Windings should be meggered at the time the motors are The power supply line for the motor should be of sufficient
put in storage. capacity to carry 125 percent of the motor’s full load current
with a maximum voltage drop of three percent on the line.
If motors have space heaters, the heaters should be ener‑
gized when the motors are placed in storage. The power supply MUST conform with motor nameplate
voltage. Motors rated 200 volts are for a 208 volt sys‑
NOTE: Remove units from containers when heaters are tem. Motors rated 230/460 volts are for a 240 or 480
energized. Reprotect if necessary. volt system. Do not use a 230 or 230/460 volt motor
If outdoor storage is necessary, protection should include on a 208 volt system.
a vapor barrier beneath the motor. The motor should be
blocked up to prevent flooding. All external parts such as Unbalanced voltages in the power supply will greatly in‑
shafts, machined surfaces, and threaded holes should be crease the internal losses of the motor, reducing the safe
protected with a rust inhibitor coating. load the motor can carry. Have the power company correct
any unbalanced voltage.
Rotate motor shaft monthly to insure that the bearing
surfaces are protected with lubricant. When motor power is supplied by overhead conductors,
it is advisable to provide a lightning arrestor on each un‑
When a motor is removed from storage, the insulation and
grounded line.
rotor movement should be checked. The insulation should
be checked by applying the potential from a 500 volt meg‑ Wire the motor to the power supply through a disconnect
ohmmeter between the windings and grounded frame for switch, short‑circuit protection, and suitable magnetic starter
10 minutes. Resistance readings should be taken at 1 and with overload protection. All wiring and fusing should be
10 minutes. Correct the readings to 40°C as discussed on in accordance with the National Electrical Code and local
page 6 of this manual. Calculate the winding polarization requirements. All motors should be connected as shown on
index by dividing the 10 minute reading by the one minute the nameplate diagram.
reading. The recommended minimum value of polarization The National Electrical Code requires a motor to be in sight
index for alternating current machine is: of the controller unless the disconnecting means can be
Class A insulation 1.5 locked open or unless there is a manually operated switch
Class B insulation 2.0 in sight of the motor which will disconnect the motor from
Class F insulation 2.0 its electrical supply.
A low polarization index indicates the insulation should be Overload protection should be installed in all three lines. Size
cleaned and dried before the motor is placed in operation. It overload heaters in starters for nameplate service factor and
is possible to operate a motor with a polarization value less amps. Overloads for 1.15 service factor motors must kick
than the minimum listed above but this is not considered out at no more than 125% of nameplate current. Overloads
good practice. for 1.0 service factor motors must kick out at no more than
115% of nameplate current.
The rotor movement is checked by rotating the shaft by
hand. If shaft is not free, contact the motor manufacturer’s Overloads should be at the same ambient temperature as
authorized repair shop. Grease in the motor bearings should motor. Do not use ambient compensated overloads.
be purged at the time of removal from storage. Refer to
LUBRICATION on pages 5 and 6.
➠
3
installation – operation
If a two-speed motor is used, be sure control characteristics OPERATION
are compatible with the motor. A two-speed single-winding
Sleeve bearing motors are usually shipped without oil and
motor requires a different starter than a two-speed two-
must be oiled before operation. Ball bearing motors are lu‑
winding motor. Starters for two-speed motors must include
bricated for the initial operation by the motor manufacturer;
a minimum time delay of 20 seconds when switching from
however, it is recommended that the grease and relief plugs
high to low speed.
be removed and the motor bearing housing be examined
When a disconnect switch is installed between motor and for presence of adequate grease before motor is placed in
starter for two speed or part winding start single- speed operation. Add grease if necessary. See instructions on pages
motor, a 6‑pole disconnect must be used. 5 and 6 for lubricating ball bearing or sleeve bearing motors.
SAFETY NOTE: Use of two 3‑pole disconnects can Turn the rotor by hand to see that it rotates freely. Motor
result in one disconnect not being off and unexpected shaft should be parallel to driven shaft so that there are no
starts or motor damage. stresses in motor frame.
If reverse operation of mechanical equipment is required, INITIAL STARTING: The motor should bring the fan up to
provide minimum time delay of two minutes before en‑ speed in less than 15 seconds. If it does not, check connec‑
ergizing motor when changing direction of rotation. tions, fuses, overloads and voltage at motor terminals during
Check the wiring system for grounds and check the start‑up period. Run the motor to check the connections
resistance between all leads for open, bad or incorrect and direction of rotation. If the rotation is incorrect, change
connections before operating the motor. any two of the three motor leads for a three phase motor
or interchange the connections of either the main or start
The conduit system should be arranged so that trapped
windings for single phase capacitor start motor.
water will collect in a sump equipped with suitable drain
and will not go into the motor terminal box. CAUTION: Excessive fan cycling may shorten the mo‑
tor's expected service life. On fans 20 feet (6 meter)
When the motor must be moved for coupling removal or belt
diameter and smaller allow for 4 to 5 starts per hour.
adjustment, a short section of flexible, watertight metallic
On larger fans, 2 or 3 starts per hour may be the limit.
conduit should be used in place of rigid conduit to protect
On two speed motors each low speed start and each
the leads to the motor.
high speed start count as one start.
Remove all water drain plugs from totally-enclosed motors.
If a two-speed motor is used, allow a time delay of a minimum
These plugs will be located in the lowest part of the installed
of 20 seconds after de‑energizing the high speed winding
motor. Because of inaccessability of drain plugs with motor
and before energizing the low speed winding. Tremendous
installed on supports, it is sometimes necessary to remove
strains are placed on driven machinery and motor unless
plugs before the motor is bolted in place.
the motor is allowed to slow to low speed rpm or less before
The drain plugs on explosion-proof motors are automatic the low speed winding is energized.
and must not be removed.
When changing fan direction of rotation, allow a minimum
NOTE: After motor is installed, it should be run for of two minutes time delay before energizing the fan motor.
three hours at least once a month, even if the tower is
DETERMINE LOAD AT MOTOR: With design water rate
not in operation. This serves to dry out windings and
and design heat load on the tower, test motor hp as follows:
relubricate bearing surfaces. If motors are purchased
with space heaters, they should be energized as soon 1. Run motor for 30 minutes. Record motor name plate
as possible. Use an auxiliary contact on the starter to data.
turn heater off when motor is running. 2. Measure voltage between all lines at motor terminals.
3. Measure amps in all three lines.
4
operation – maintenance
4. Average the measured volts and amps and calculate Factor (75°F) 100.8
hp (75°F) = hp (40°F) X = 7.8 x = 7.43
test horsepower using the following equation: Factor (40°F) 105.9
Volts x Amps (average) If it is desired to correct for high or low test barometric
hp (test) = x hp (nameplate)
Volts x Amps (nameplate) pressure, multiply the predicted horsepower by standard
station barometric pressure and divide by test station
5. For a given fan pitch setting and RPM, horsepower will barometric pressure.
vary directly with the air density which is a function of *Use ambient dry‑bulb temperatures if checking a forced
temperature and barometric pressure. Because fans are draft cooling tower.
generally pitched for summer weather horsepower, it is
Fan motor overloads sized for summer weather will
expected that the motor nameplate horsepower will be
handle the higher winter horsepower without adjustment
exceeded during winter operation. Assuming 100% heat
providing they are at the same ambient temperature as
load, the temperature rise in the motor will be greater at
the motor and there is ample heat load on tower.
the higher horsepower, but the operating temperature
of the motor will actually be lower due to the drop in NORMAL OPERATION: Class B insulated motors are rated
ambient temperature. Under these conditions, the higher at a maximum total operating temperature of 130°C (266°F).
horsepower should not be detrimental to the motor. A thermometer in contact with the winding may indicate a
temperature up to 100°C (212°F). on a protected motor or
If the horsepower measurement is taken during cold
up to 115°C (239°F) on a totally enclosed motor without the
weather conditions, the predicted horsepower which will
motor being too hot. Therefore, a motor that appears to be
result during summer operation may be determined by
hot is not necessarily overloaded. Check with thermometers.
applying the Factor from Figure 1. For a given location,
the barometric pressure will not normally vary enough CAUTION: Normal operating temperatures of electric
to cause significant error and for this reason, has not motors can be hot enough to cause burns. Avoid any
been included in the Factors. unprotected contact with the surface of an operating
motor.
96
97 MAINTENANCE
98 SAFETY NOTE: When working on the fan or fan drive,
make sure the electric motor cannot be started. See
99 "Installation" section.
100 To obtain maximum motor life, establish a schedule of main‑
101 tenance based on the particular application of the motor and
observe the following procedures and precautions:
FACTOR
102
CLEANING: Remove any oil, dust or scale deposits from the
103 motor. They can cause excessive insulation temperatures.
104 LUBRICATION:
105 Ball Bearing Motors: The following table may be used as
a guide in determining greasing periods for motors:
106 Figure 1
107
108 Duty 1 – 30 hp 40 – 250 hp
0 10 20 30 40 50 60 70 80 90 100
I n te rm itte n t 12 m on ths 12 m on th s
Example: The horsepower on an induced draft cooling tower* is
8 to 16 h ou rs pe r da y 12 m on th s 6 m on th s
7.8 hp on a 40°F ambient wet‑bulb day. What is the predicted
hp on a 75°F ambient wet‑bulb day? Con tin u ou s 8 m on th s 4 m on th s
5
operation – maintenance
All greases will deteriorate in time depending upon bearing race. If the bearing feels rough or binds in spots, it should
size, speed and temperature. The grease used should be be replaced.
recommended by the motor manufacturer. See instructions Sleeve Bearing Motors: Check oil in sleeve bearings at
attached to motor for recommended lubricant. If these least every three months. When journal size is less than two
instructions have been lost or misplaced, obtain informa‑ inches, stop the motor to check the oil level. Old oil should
tion on lubricant to use and local supply source from motor be drained and replaced at least every year. Clean out oil
manufacturer’s nearest authorized service facility or from well if there is evidence of dirt and sludge.
the motor manufacturer. Give complete motor nameplate
data and state clearly that the motor is used on a water Motor shaft must be stopped when motor is oiled. The
cooling tower. Chevron SRI‑2 is recognized by many motor oil used should be a good grade of mineral oil of light or
manufacturers as a suitable grease for ball bearing motors medium viscosity (such as SAE No. 10). Turbine oil rather
for cooling tower service. In general, a polyurethane or lithium than automotive crankcase oil is recommended.
base grease with rust and oxidation inhibitors is recom‑ Check bearing wear yearly by measuring the air gap with a
mended. Use a grease of NLGI No. 2 consistency. Do not feeler gauge. Measure gap in at least four equally spaced
mix greases which are of different types or specifications. positions at each end of the motor with two of the places
If a change is desired, the motor bearing housing grease being the lowest point and the point subject to the load pull.
reservoir should be completely cleaned of old grease before INSULATION: Check insulation resistance with a meg‑
repacking with new grease. ohmmeter at the end of each shutdown period. Apply the
The relief method of greasing motors tends to purge the megohmmeter potential to the winding for one minute
bearing housing reservoir of used grease by forcing out before taking a reading. Correct the reading to 40°C by
old grease with new grease. Use a plunger type grease using the equation:
gun which will not fit the bearing grease fill hole too tightly. R40°C= Kt x Rt and the curve below
Either an excess or insufficient amount of lubricant in the
bearings can cause overheating. To prevent this occurrence, 100
use the following greasing procedure:
50
1. Stop motor.
2. Wipe grease plugs, outside of bearing housing, and
relief plug, clean.
Insulation Resistance Temperature Coefficient Kt
3. Remove grease and relief plugs and free relief hole of
10
any hardened grease. Use a thin piece of wire in open‑
ing.
5
4. Add grease with a hand operated pressure gun until
new grease appears at the relief hole. Take special care
when greasing the fan end bearing of TEFC motors. The
long relief might be too small for the bearing to relieve
properly. 1.0
5. Run the motor for approximately one hour after greasing
0.5
to permit rotating parts of the bearing to expel excess
grease. Take out some of the excess grease with a thin
piece of wire.
6. Replace plugs and wipe the outside of the bearing
housing clean. 0.1
Every few years the motor end brackets should be removed 0.05
To Convert Observed Insulation Resistance Rt to 40°C
and the grease reservoirs cleaned and repacked full with Multiply by the Temperature Coefficient Kt , Rc – Rt x Kt
approved ball bearing grease. Open bearings should be -10 0 10 20 30 40 50 60 70 80 90 100
cleaned and repacked.
Winding Temperature °C
Bearings should be checked for "roughness" by turning the
outer race slowly with the fingers while holding the inner Approximate Insulation Resistance Variation with Temperature
for Rotating machines.
6
maintenance
A record of these corrected readings will show a trend in Do not start motor without determining that there will
the insulation condition. It is considered good practice to be no interference with free rotation of the fan drive.
recondition a winding if the resistance, having been high on
previous readings, drops to near the recommended minimum MOTOR WARRANTY
value as calculated by:
Motor manufacturers’ warranties run for 12 months in service
Megaohms = 1000 + Rated Voltage of Machine but not to exceed 18 months from date of manufacture. Mo‑
1000 tor manufacturers warrant their products to be of the type
and quality described, suitable for the service for which they
Motors in continuous operation will stay at a temperature
are supplied, and free of defects in materials and workman‑
sufficiently above ambient temperature to prevent conden‑
ship. Failures from causes external to the motor (e.g., single
sation of moisture on and about the windings, even if the
phasing, operation under prolonged or extensive overload,
location is very humid. Idle motors, however, accumulate
damage from handling, improper maintenance, use on other
moisture readily which causes gradual deterioration of in‑
than the service for which supplied, defect in wiring to power
sulation. Where motors are idle for a long time, single‑phase
supply, or deficiency or defect in controls) are not covered
heating or space heaters may be required to prevent water
by the motor manufacturers’ warranties.
condensation.
If a motor failure occurs within the warranty period
Check insulation resistance at least once a year with the because of defect in material or workmanship, the
motor at normal operating temperature. Comparison with motor manufacturer is liable and has the right to
several previous readings will give an indication of improve‑ remedy the failure by adjustment, repair, or supplying
ment or deterioration of insulating value. Readings, to have a replacement motor F.O.B. his factory or authorized
comparison value, should be taken under the same condi‑ repair facility. In such event, the motor must be delivered
tions (temperature, operating time since last shutdown, etc.). to the nearest repair facility authorized by the motor
Low or falling resistance readings indicate the need for manufacturer with notification that the motor is from
maintenance. Contact the nearest repair facility authorized a Marley product and that warranty consideration is
by the motor manufacturer for repair service. requested. Prompt notification of such failure should
be directed to a Marley sales representative.
VIBRATION: If vibration occurs, it should be corrected
without delay. Use the following procedure to determine Motor manufacturers will not accept warranty obligation
source of trouble: for repair of motors by other than their authorized repair
1. Check motor mounting to see that fasteners are tight. facility nor warranty obligation for materials or workman‑
ship employed in making repairs. Repair shops, including
2. Disconnect motor from load and run motor separately.
authorized repair facilities, generally warrant their material
If motor still vibrates, rebalance rotor.
and workmanship for a period of 12 months.
3. If vibration is in mechanical equipment*, check:
Motor manufacturers’ warranties do not cover cost of
a. Alignment of motor with mechanical equipment. dismounting, transportation to and from repair facilities, or
b. Tightness of Geareducer, or belt driven components, remounting motors.
mounting bolts.
c. Unbalance in drive shaft or fan. MOTOR OPERATION NOTE:
*Refer to service manuals for operating and maintenance Higher density of cold air at fan increases motor horsepower.
recommendations. If motor overloads will not allow fan motor operation at high
speed in forward direction, one of the following might be done:
SEASONAL SHUTDOWN 1. If overloads are adjustable, set at a higher value
If a motor is used only seasonally, it should be cleaned and (+15%) for cold weather operation. Readjust for sum‑
lubricated at the close of each season. Refer to motor manu‑ mer operation.
facturer’s recommendations for lubrication and maintenance 2. Operate motor (fan) in reverse (reverse 2 loads).
instructions. At start of new season, make sure bearings are 3. Operate two‑speed motor at low speed.
adequately lubricated before returning motor to operation.
When tower is not in operation, the motor should be run
for three hours at least once a month. This serves to dry
out windings and relubricate bearing surfaces.
7
cooling tower Motor
SPX COOLING TECHNOLOGIES, INC.
7401 WEST 129 STREET Z0239042_A | ISSUED 06/2016
OVERLAND PARK, KS 66213 USA COPYRIGHT © 2016 SPX CORPORATION
913 664 7400 | spxcooling@spx.com In the interest of technological progress, all products are subject to design
spxcooling.com and/or material change without notice.
