HP H2H3, N2H3 manual Defrost System, Defrost Thermostat, Defrost Control Board

INSTALLATION INSTRUCTIONS 3-phase R-22 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 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.

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

OF1

C

US

K1

R21

C2

D13

01A 5501A

C19

OF2

D4

JW2 C10

C4

R8

R7

C9

JW1

C1

A29

R9

-

CEBD430524

1

U1

D10

C17

D1

D2

R26

D6

R28

C7

JW3

C13

R4

D3

C16

U3

HK32EA001

1

R11

R20

R1 R2

R3

R5

1

DFT

P3

Y

J2

P2

1

W1

30 60 90

T1 C C O

P1

J1

1

1

SPEEDUP

O

R

W2

Y

C

506 01 5001 00 11