HP H2H3, N2H3 DEFROST SYSTEM

INSTALLATION INSTRUCTIONS

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 14 and confirm that the thermostat is securely fastened in place on the tube stub.

Figure 14 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 15). 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 15). 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.

506 01 5001 00

3-phase R-22 Split System Heat Pump

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 15).

Figure 15	Defrost Control Board
H9C1→	O1 R6	R14 R13

CUS

	OF1		K1
					R21
					C2				D13
5501A01A		OF2		A29	R9	JW1	JW2 C10	C4	R8	R7
	C19	C9			D4
-	D1	D2 R26	C1		D3	C16	C7	JW3	C13		U3
CEBD430524 D10
							1	U1
								C17
					D6	R28					R4
							1	R1 R2	R3	R11	R5 HK32EA001
							R20
			1		DFT	P3
				Y			J2
			P2			1					W1
	T1 C C O							30 60 90
					P1		J1
								1
					1

SPEEDUP

O

R

W2

Y

C

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