Heat Controller HP Series Installation, Operation & Maintenance Manual page 27

Heat Controller, Inc.
Thermostat Connections
The thermostat should be wired directly to the CXM
board. See "Electrical – Thermostat" for specific terminal
connections.
Figure 21: Low Voltage Field Wiring
Contactor - CC
Transformer
24
ELECTRICAL - LOW VOLTAGE WIRING
Capacitator
Circ Brkr
Loop PB1 HWG PB2
Grnd
BR
CXM Control
CB
Low Voltage
Connector
Rev.: 3/24/00
HP SerieS
Low Water Temperature Cutout Selection
The CXM control allows the field selection of low water
(or water-antifreeze solution) temperature limit by clipping
jumper JW3, which changes the sensing temperature
associated with thermistor FP1. Note that the FP1
thermistor is located on the refrigerant line between the
coaxial heat exchanger and expansion device (TXV).
Therefore, FP1 is sensing refrigerant temperature, not water
temperature, which is a better indication of how water flow
rate/temperature is affecting the refrigeration circuit.
The factory setting for FP1 is for systems using water
(30°F [-1.1°C] refrigerant temperature). In low water
temperature applications with antifreeze (most ground
loops), jumper JW3 should be clipped as shown in Figure
22 to change the setting to 10°F [-12.2°C] refrigerant
temperature, a more suitable temperature when using
an antifreeze solution. All residential units include
water/refrigerant circuit insulation to prevent internal
condensation, which is required when operating with
entering water temperatures below 59°F [15°C].
Figure 22: FP1 Limit Setting
CXM PCB
26
Installation, Operation & Maintenance
JW3-FP1
jumper should
be clipped for
low temperature
operation