Service manual

THE SMART SOLUTION FOR ENERGY EFFICIENCY
Vertical Stack
Rev.: 11/09/12
21
climatemaster.com
Electrical Wiring - Low Voltage
Thermostat Connections - The thermostat should be
wired directly to the CXM or DXM board. See “Electrical
– Thermostat” for specifi c terminal connections. Review
the appropriate AOM (Application, Operation and Main-
tenance) manual for units with DDC controls.
Low Water Temperature Cutout Selection - The CXM/
DXM control allows the fi eld selection of low water (or
water-antifreeze solution) temperature limit by clipping
jumper JW3, which changes the sensing temperature as-
sociated with thermistor FP1. Note that the FP1 thermis-
tor is located on the refrigerant line between the coaxial
heat exchanger and expansion device (TXV or cap tube).
Therefore, FP1 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 FP1 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 5 to change the setting to
10°F [-12.2°C] refrigerant temperature, a more suitable
temperature when using an antifreeze solution. All
ClimateMaster units operating with entering water
temperatures below 59°F [15°C] must include the
optional water/refrigerant circuit insulation package to
prevent internal condensation.
Figure 5: FP1 Limit Setting
CXM PCB
JW3 should never be clipped for equipment or systems
without antifreeze.
JW3-FP1 jumper
should be clipped
for low tempera-
ture operation