Carrier 19XL - Manual (Page 89)

relay can only accomplish this if the relay has been added to the cooling tower temperature
controller. The TOWER FAN RELAY is turned on whenever the CONDENSER WATER PUMP
is running, flow is verified, and the difference between cooler and condenser pressure is more
than 45 psid (310 kPad) (30 psid [207 kPad] for HFC-134a) or entering condenser water
temperature is greater than 85 F (29 C). The TOWER FAN RELAY is deenergized when the
condenser pump is off, flow is lost, the evaporator refrigerant temperature is less than the
override temperature, or the differential pressure is less than 40 psid (279 kPad) (28 psid [193
kPad] for HFC-134a) and entering condensing water is less than 80 F (27 C).
IMPORTANT: A field-supplied water temperature control system for condenser water
should be installed. The system should maintain the leaving condenser water tempera-
ture at a temperature that is 20° F (11° C) above the leaving chilled water temperature.
CAUTION CAUTION
!
The tower-fan relay control is not a substitute for a condenser water temperature
control. When used with a Water Temperature Control system, the tower fan
relay control can be used to help prevent low condenser water temperatures.