SPX Cooling Technologies CoolingTower Marley MCW - Manual (Page 14)

14
Caution
When operating in this mode care must be taken not to exceed a total
acceleration time of 30 seconds per hour.
Fan cycling limits: From a dead stop, determine the number of sec-
onds it takes the fan to arrive at full speed. Divide this number into 30
to determine the allowable number of starts per hour. Considering the
normal fan and motor sizes utilized on MCW towers, anticipate that
approximately 4 to 5 starts per hour are allowable.
A cooling tower equipped with a two-speed motor, has a greater
opportunity for temperature control. When the water temperature
becomes too cold, switching the fan to half-speed will cause the cold
water temperature to rise—stabilizing at a temperature a few degrees
higher than before. With a further reduction in water temperature, the
fan may be cycled alternately from half-speed to off—subject to the
same constraint of 30 seconds of allowable acceleration time per hour
as outlined above.
If your tower consists of two or more cells, cycling of motors may
be shared between cells, increasing your steps of operation accord-
ingly.
Multiple fan motors serving a single fill section must be cycled simul-
taneously. This applies to models 901146 thru 901157, 901556 thru
901558, 901756 thru 901758 and 901956 thru 901959 MCW models.
Multicell towers equipped with two-speed motors will maximize energy
savings and minimize sound levels if fans are staged so that all fans
are brought up to low speed before any fan goes to high speed.
For greater insight on cold water temperature control, please read
“Cooling Tower Energy and its Management”, Technical Report
#H-001-A, available spxcooling.com.
Operation
Caution