Heat Controller HEV Series Installation, Operation & Maintenance Manual page 24

Installation, Operation & Maintenance
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
ELECTRICAL - LOW VOLTAGE WIRING ELECTRICAL - LO
DXM2
Capacitator
Circ Brkr
Loop PB1 HWG PB2
Grnd
BR
DXM 2
CXM Control
CB
Low Voltage
Connector
Rev.: 3/24/00
HEV/H SERIES
Low Water Temperature Cutout Selection
The DXM2 control allows the fi eld selection of low water (or
water-antifreeze solution) temperature limit by clipping jumper
JW3, which changes the sensing temperature associated
with thermistor LT1. Note that the LT1 thermistor is located on
the refrigerant line between the coaxial heat exchanger and
expansion device (TXV). Therefore, LT1 is sensing refrigerant
temperature, not water temperature, which is a better
indication of how water fl ow rate/temperature is affecting the
refrigeration circuit.
The factory setting for LT1 is for systems using water (30°F
[-1.1°C] refrigerant temperature). In low water temperature
(extended range) applications with antifreeze (most ground
loops), jumper JW3 should be clipped as shown in Figure
19 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: LT1 Limit Setting
Fault
Off
S3
c1
ay
c2
ay
P11
AO2
JW3-LT1 jumper should be clipped
for low temperature operation
24
Status
On
JW3
Off On
Off On
CCH
Relay
S2
A0-1 A0-2
S1
P10
Gnd T1 T2 T2 T3 T3 T4 T4
Heat Controller, Inc.
HP
LP
LP
LT1
LT1
LT2
LT2
RV
RV
CO
12
CO
P7
RV
Relay
1
24Vdc
EH1
4
EH2
P6
Comp
Relay
CCG
CC
P9
T5 T5 T6 T6
DXM2 PCB