User manual

Warning

Caution

atmospheric moisture from the entering air. Such lightly wetted areas are

most subject to freezing.

Therefore, if excessive ice forms on the louvers, stop the fan for a few

minutes. With the fan off, the water ﬂow will increase in the vicinity of the

louvers and reduce the ice buildup.

3. Under extended extreme cold conditions, it may be necessary to operate

the fan in reverse. This forces warm air out through the louvers, melting any

accumulated ice—adequate heat load must be available. Reversal may be at

either full or half speed; however, reversal at half speed is recommended.

Reverse operation of the fan should be used sparingly and should only

be used to control ice, not to prevent it. Reverse fan operation should not

need to exceed 1 or 2 minutes. Monitoring is required to determine the time

required to melt accumulated ice.

Reverse operation of fans for prolonged periods during subfreezing

weather can cause severe damage to fans and fan cylinders. Ice can

accumulate inside fan cylinders at fan blade plane of rotation and

fanbladetipswilleventuallystrikethisringofice,damagingthe

fan blades or cylinder. Ice can also accumulate on fan blades and

be thrown off, damaging fan cylinder or blades. Allow a minimum

of 10 minute delay between reverse operation and forward opera-

tion during subfreezing weather to permit ice to dissipate from fan

blades and fan cylinders. See Fan Drive Caution note on page 12

for fan speed change and reversing precautions.

Intermittent Wintertime Operation:

If periods of shutdown (nights, weekends, etc.) occur during freezing weather,

measures must be taken to prevent the water in the cold water basin—and all

exposed pipework—from freezing. Several methods are used to combat this,

including automatic basin heater systems and pump freeze protection systems

available from Marley.

Basin heaters systems will not prevent the coil from freezing.

Unless some means of freeze prevention is incorporated into your

system,thetowerbasinandexposedpipeworkshouldbedrained

at the beginning of each wintertime shutdown period.

If tower basin is drained, verify that all basin heaters have been shut

off either by automatic cutoff or disconnect switch.

Operation