22
3.
Water flow rate:
Increasing the water flow rate (GPM or L/s) will cause
a slight elevation in cold water temperature, while reducing the water
flow rate will cause the cold water temperature to decrease slightly.
However, at a given heat load (see formula above), water flow
reductions
also cause an increase in the incoming hot water
temperature. Use care to prevent the hot water from exceeding 120
°
F,
(49
°
C) in order to prevent damage to the tower components.
4.
Air flow rate:
Reducing air flow through the tower causes the cold
water temperature to rise.
This is the approved method by which to
control leaving water temperature.
If your tower is equipped with a single-speed motor, the motor may be
shut off when the water temperature becomes too cold. This will cause
the water temperature to rise. When the water temperature then
becomes too warm for your process, the motor can be restarted.
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
seconds 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 Primus towers, anticipate
that approximately 4 to 5 starts per hour are allowable.
If your tower is equipped with a two-speed motor, you will enjoy 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 accordingly.
For greater insight on cold water temperature control, please read
“Cooling Tower Energy and its Management,”
Marley Technical
Report #H-001-A, available from your Marley sales representative.
Operation
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Caution
Summary of Contents for Primus P11
Page 1: ...Manual 04 131 User Manual Models P11 through P15 ...
Page 39: ...39 ...
