Heat Controller HTD Series, Installation, Operation & Maintenance Manual

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22
Installation, Operation & Maintenance
HTV/HTD/HTH SERIES
Heat Controller, Inc.
Electrical - Low Voltage Wiring
Figure 20: Accessory Wiring
Accessory Connections
A terminal paralleling the compressor contactor coil has been
provided on the CXM control. Terminal “A” is designed to control
accessory devices, such as water valves. Note: This terminal
should be used only with 24 Volt signals and not line voltage.
Terminal “A” is energized with the compressor contactor. See
Figure 20 or the specifi c unit wiring diagram for details.
Water Solenoid Valves
An external solenoid valve(s) should be used on ground water
installations to shut off fl ow to the unit when the compressor
is not operating. A slow closing valve may be required to help
reduce water hammer. Figure 20 shows typical wiring for a
24VAC external solenoid valve. Figures 21 and 22 illustrate
typical slow closing water control valve wiring for Taco 500 series
(Manufacturer P/N AVM...) and Taco SBV series valves. Slow
closing valves take approximately 60 seconds to open (very little
water will fl ow 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.
Two-stage Units
HT two-stage units should be designed with two parallel valves
for ground water applications to limit water use during fi rst stage
operation. For example, at 1.5 gpm/ ton [2.0 l/m per kW], a 048
unit requires 6 gpm [23 l/m] for full load (2nd stage) operation,
but only 4 gpm [15 l/m] during 1st stage operation. Since the unit
will operate on fi rst stage 80-90% of the time, signifi cant water
savings can be realized by using two parallel solenoid valves with
two fl ow regulators. In the example above, stage one solenoid
would be installed with a 4 gpm [15 l/m] fl ow regulator on the
outlet, while stage two would utilize a 2 gpm [8 l/m] fl ow regulator.
When stage one is operating, the second solenoid valve will be
closed. When stage two is operating, both valves will be open,
allowing full load fl ow rate.
Figure 23 illustrates piping for two-stage solenoid valves. Review
fi gures 20-22 for wiring of stage one valve. Stage two valve should
be wired between terminal “Y2” (ECM board) and terminal “C.”
Note: When EWT is below 50°F [10°C], a minimum of 2 gpm per
ton (2.6 l/m per kW) is required.
Figure 21: AVM Valve Wiring
C
C
Thermostat
Y1
1
2
3
Y1
AVM
Taco Valve
Heater Switch
Figure 22: Taco SBV Valve Wiring
From Water Source
IN
OUT
NOTE: Shut-off valves, strainers and
other required components not shown.
Solenoid
Valve
Flow
Regulator
To Discharge
Stage 1
Stage 2
Figure 23: Two-Stage Piping