INSTALLATION INSTRUCTIONS

3-phase R-410A Split System Heat Pump

 

 

DEFROST SYSTEM

A. DEFROST THERMOSTAT

The defrost thermostat is factory installed on a short tube stub extending from the coil end plate. Refer to Figure 12 and confirm that the thermostat is securely fastened in place on the tube stub.

Figure 12

Defrost Thermostat

 

 

FEEDER TUBE

TUBE STUB

COIL

DEFROST

THERMOSTAT

B. DEFROST CONTROL BOARD

The defrost board is a time/temperature control which includes a field-selectable time period between defrost cycles of 30, 60, or 90 minutes (quick-connects located at board edge, factory set at 90 minutes).

Defrost mode is identical to cooling mode except that outdoor-fan motor stops and second-stage heat is turned on to continue warming conditioned space.

Initially, the defrost cycle timer starts when the contactor is energized and a 24 VAC signal is present on the T1 terminal. Then the defrost cycle begins when the defrost thermostat is closed and the cycle timer times out (30, 60, 90 or minutes).

To initiate a forced defrost cycle, the defrost thermostat must be closed. This can be accomplished as follows:

1.Turn off power to outdoor unit.

2.Disconnect outdoor fan-motor lead from OF2 on control board (refer to Figure 13). Tape lead to prevent grounding.

3.Restart unit in heating mode, allowing frost to accumulate on outdoor coil.

4.After a few minutes in heating mode, liquid line temperature should drop below closing point of defrost thermostat (approximately 32 °F).

5.Short between speed-up terminals with a flat-bladed screwdriver (refer to Figure 13). This reduces the timing sequence to 7, 14, or 21 seconds (30, 60, or 90 minute defrost selection, respectively).

6.When you hear reversing valve change position, remove screwdriver immediately; otherwise, control will terminate normal 10-minute defrost cycle in approximately 2 seconds.

NOTE: Length of defrost cycle is dependent upon length of time it takes to remove screwdriver from test pins after reversing valve has shifted.

7.Unit will remain in defrost for remainder of defrost-cycle time or until defrost thermostat reopens at approximately 65 °F coil temperature of liquid line.

8.Turn off power to outdoor unit and reconnect fan-motor lead to OF2 on control board (refer to Figure 13).

 

Figure 13

 

Defrost Control Board

 

 

 

 

 

 

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506 01 5102 00

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HP H4H3 manual Defrost System, Defrost Thermostat, Defrost Control Board

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