Heat Controller HTH, HTV, HTD manual Accessory Connections, Two-stage Units

Installation, Operation & Maintenance HTV/HTD/HTH SERIES Heat Controller, Inc.

Electrical - Low Voltage 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 specific unit wiring diagram for details.

Figure 20: Accessory Wiring

Water Solenoid 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 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 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.

Two-stage Units

HT two-stage units should be designed with two parallel valves for ground water applications to limit water use during first 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 first stage 80-90% of the time, significant water savings can be realized by using two parallel solenoid valves with two flow regulators. In the example above, stage one solenoid would be installed with a 4 gpm [15 l/m] flow regulator on the outlet, while stage two would utilize a 2 gpm [8 l/m] flow 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 flow rate.

Figure 23 illustrates piping for two-stage solenoid valves. Review figures 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 Y1

2	3	AVM
1		Taco Valve
Heater Switch

C Y1

Thermostat

Figure 22: Taco SBV Valve Wiring

Figure 23: Two-Stage Piping
Solenoid	Flow
Valve
	Regulator
Stage 2
OUT	To Discharge
Stage 1

IN From Water Source

NOTE: Shut-off valves, strainers and other required components not shown.

22