Carrier 50RTG specifications Low Voltage Wiring, Pre-Start-Up

Step 8 — Low Voltage Wiring

THERMOSTAT CONNECTIONS — The thermostat should be wired directly to the Aquazone™ control board. See Fig. 4 and 5.

WATER FREEZE PROTECTION — The Aquazone control allows the field selection of source fluid freeze protection points through jumpers. The factory setting of jumper JW3 (FP1) is set for water at 30 F. In earth loop applications, jumper JW3 should be clipped to change the setting to 13 F when using antifreeze in colder earth loop applications. See Fig. 6.

AIR COIL FREEZE PROTECTION — The air coil freeze protection jumper JW2 (FP2) is factory set for 30 F and should not need adjusting, unless using anti-freeze.

ACCESSORY CONNECTIONS — Terminal labeled A on the control is provided to control accessory devices such as water valves, electronic air cleaners, humidifiers, etc. This sig- nal operates with the compressor terminal. See Fig. 7. Refer to the specific unit wiring schematic for details.

NOTE: The A terminal should only be used with 24 volt signals — not line voltage signals.

WATER SOLENOID VALVES — Water solenoid valves may be used on primary secondary pump and ground water installa- tions. A typical well water control valve wiring which can limit waste water in a lockout condition is shown in Fig. 7. A slow closing valve may be required to prevent water hammer. When using a slow closing valve, special wiring conditions need to be considered. The valve takes approximately 60 sec- onds to open (very little water will flow before 45 seconds) and it activates the compressor only after the valve is completely opened by closing its end switch. When wired as shown, the valve will have the following operating characteristics:

1.Remain open during a lockout.

2.Draw approximately 25 to 35 VA through the “Y” signal of the thermostat.

IMPORTANT: This can overheat the anticipators of electromechanical thermostats. Only use relay based electronic thermostats.

	Capacitor
	Circ Brkr
	Grnd
Contactor-CC
L2	L1
	BR
Transformer
	Aquazone “C”
CB	See Note
THERMOSTAT	Low Voltage
	Connector
WIRED DIRECTLY
TO CONTROL
BOARD

NOTE: Low voltage connector may be removed for easy installation.

Fig. 5 — Low Voltage Field Wiring

AQUAZONE CONTROL (C Control Shown)

Fig. 6 — Typical Aquazone Control Board

Jumper Locations

Terminal Strip P2

C

Typical

24 VAC Water

Valve

A

Fig. 7 — Typical D Control Accessory Wiring

PRE-START-UP

System Checkout — When the installation is complete and the system is cleaned and flushed, follow the System Checkout procedure outlined below.

1.Voltage: Ensure that the voltage is within the utilization range specifications of the unit compressor and fan motor.

2.System Water Temperature: Ensure that the system water temperature is within an acceptable range to facili- tate start-up. (When conducting this check, also verify proper heating and cooling set points.)

3.System Water pH: Verify system water acidity (pH = 7.5 or 8.5). Proper pH promotes the longevity of hoses and heat exchangers.

4.System Flushing: Properly clean and flush the system periodically. Ensure that all supply and return hoses are connected end-to-end to facilitate system flushing and prevent fouling of the heat exchanger by system water. Water used in the system must be potable and should not contain dirt, piping slag, and chemical cleaning agents.

5.Closed-Type Cooling Tower or Open Tower with Heat Exchanger: Check equipment for proper temperature set points and operation.

6.Verify Balanced Water Flow Rate to Heat Pump.

7.Standby Pump: Verify that the standby pump is properly installed and in operating condition.

8.Access Panels: Assure that all access panels in the filter and fan section are securely closed.

9.Air Dampers: Assure that all air dampers are properly set.

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