22
Installation, Operation & Maintenance - HKV Series
Electrical - Power & Low Voltage Wiring
ELECTRICAL - LOW VOLTAGE WIRING
Thermostat Connections
- The thermostat will be wired
to the CXM/DXM2 board located within the unit control
box. Refer to the unit wiring diagram for specific details.
Low Water Temperature Cutout Selection
- The CXM/
DXM2 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 LT1. Note that the LT1
thermistor is located on the refrigeravnt 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 flow 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 17 to change the setting to
10°F [-12.2°C] refrigerant temperature, a more suitable
temperature when using an antifreeze solution. All
Comfort-Aire/Century units operating with entering
water temperatures below 60°F [15.6°C] must include the
optional water/refrigerant circuit insulation package to
prevent internal condensation.
Accessory Connections -
A terminal paralleling the
compressor contactor coil has been provided on the DXM2
control. Terminal “A” is designed to control accessory
devices. Note: This terminal should be used only with 24
Volt signals and not line voltage. Terminal “A” is energized
with the compressor contactor.
The DXM2 controller includes two accessory relays ACC1
and ACC2. Each relay includes a normally open (NO) and
a normally closed (NC) contact. Accessory relays may be
configured to operate as shown in the tables below.
Accessory Relay 2 Configuration
Accessory Relay 1 Configuration
DIP 2.1
DIP 2.2
DIP 2.3
ACC1 Relay Option
ON
ON
ON
Cycle with fan
OFF
ON
ON
N/A for Residential Applications
ON
OFF
ON
Water valve – Slow opening
ON
ON
OFF
Outside air damper
OFF
ON
OFF
ClimaDry option – Dehumidistat
OFF
OFF
OFF
ClimaDry option – Humidistat
OFF
OFF
ON
N/A for Residential Applications
ON
OFF
OFF
N/A for Residential Applications
All other DIP combinations are invalid
DIP 2.4
DIP 2.5
DIP 2.6
ACC2 Relay Option
ON
ON
ON
Cycle with compressor
OFF
ON
ON
N/A for Residential Applications
ON
OFF
ON
Water valve – Slow opening
OFF
OFF
ON
Humidifier
ON
ON
OFF
Outside air damper
All other DIP combinations are invalid
Water oleniod Valves - An external solenoid valve(s) should be used
on ground water installations to shut off flow to the unit when the
compressor is not operating.
A slow closing valve may be required to help reduce
water hammer. Figure 18 shows typical wiring for a 24VAC
external solenoid valve. Figures 19 and 20 illustrate
typical slow closing water control valve wiring for Taco
500 series (Comfort-Aire/Century P/N AVM) and Taco
SBV series valves. Slow closing valves take approximately
60 seconds to open (very little water will flow before 45
seconds). Once fully open, an end switch allows the
compressor to be energized. Only relay or triac based
electronic thermostats should be used with slow closing
valves. When wired as shown, the slow closing valve will
operate properly with the following notations:
1. The valve will remain open during a unit lockout.
2. The valve will draw approximately 25-35 VA through
the “Y” signal of the thermostat.
Note: This valve can overheat the anticipator of an
electromechanical thermostat. Therefore, only relay or
triac based thermostats should be used.