Operation Of The WSHP Loop Controller
WSHP Unit Compressor Enable
If after the Lead/Lagged pump activates and Proof of Water Flow has
been established, the System Active relay is energized and when AZ
2 Controllers are being used for the WSHP units, a Global enable is
broadcast to the controllers letting them know to enable their compres-
sors. If using another control system for the WSHP units the System
Active relay would be used to send a 24 V relay signal to the units to run.
Heat Rejection
Staged Cooling
The GPC-XP Loop Controller monitors the loop water temperature to
determine if the loop water needs to be cooled. If the loop water tempera-
ture rises above a user defined setpoint the GPC-XP Loop Controller will
energize the cooling tower spray pump. This will remain on if the spray
pump proof of flow proves flow until the setpoint temperature is satisfied.
This acts as the first stage of heat rejection. If the loop water temperature
continues to rises above a second set of user defined setpoints the cooling
tower fan will be energized providing a second stage of cooling for the
water flowing through the cooling tower.
Modulating Cooling
The GPC-XP Loop Controller has the ability of sending a modulating
signal to the cooling tower fan if equipped with a VFD, to provide an
increase or decrease using a direct acting floating point control of the
output signal for modulating the cooling tower fan VFD.
Heat Addition
Staged Heating
The GPC-XP Loop Controller monitors the loop water temperature to
determine if the loop water needs to be heated. If the loop water tem-
perature falls below a user defined setpoint the GPC-XP Loop Control
-
ler will energize the Cool Bypass Valve and enable the heat addition
device. This will remain on if the boiler proof of flow proves flow until
the setpoint temperature is satisfied.
Modulating Heating
The GPC-XP Loop Controller has the ability of sending a modulating
signal to a modulating mixing valve or a variable heat source. When
the loop water temperature drops below a user defined setpoint, the
Cool Bypass Valve will be energized and the analog output voltage
will increase or decrease using a reverse acting floating point control to
modulate a valve or variable heat source.
Emergency Shutdown
The GPC-XP Loop Controller uses an Emergency Shutdown input on
one of the binary inputs from a firestat or smoke detector (by others) to
force shutdown of the entire system should a safety condition be initi-
ated by the safety device. It is configured as a Normally Closed (NC)
contact that is only active when the circuit is opened.
Operation
7
WSHP Loop Controller
GPC-XP Guide
