Bryant R-22 service manual JumperDFT and R Terminals

G

E

W2 14

L

W3

R

Y

O

C

30 50

W1

OF2 OF1

GC R C

R C Y C

O DFT

	OF2
OF1
O	R T2 Y	TI DFT	C	TEST 30 50 90
				W1
O
R
W2
Y
C
CES0110063,
CES0130024

	HK32FA003/HK32FA006		A88402		A91442
		Fig. 19—Jumper DFT and R Terminals
2. Using thermocouple temperature-measuring device, route				4.	Jumper between DFT and R terminals on control board as
	sensor or probe underneath coil (or other convenient loca-				shown in Fig. 21.
	tion). Attach to liquid line near defrost thermostat. Insulate			5.	Disconnect outdoor fan-motor lead from OF2. Tape lead to
	for more accurate reading.				prevent grounding.
3.	Turn on power to outdoor unit.			6.	Turn on power to outdoor unit.
4. Restart unit in heating mode.				7.	Restart unit in heating mode, allowing frost to accumulate
					on outdoor coil.
5. Within a few minutes, liquid-line temperature drops within
				8.	After a few minutes in heating mode, liquid-line tempera-
	a range causing defrost thermostat contacts to close. Tem-
					ture at defrost thermostat should drop below closing set
	perature range is from 33°F to 27°F. Notice temperature at
					point of defrost thermostat of approximately 30°F. Check
	which ohmmeter reading goes from	∞	to zero ohms.
					resistance across defrost thermostat leads using ohmmeter.
	Thermostat contacts close at this point.
					Resistance of zero indicates defrost thermostat is closed and
6. Remove protective cover from TP1 and			TP2 speed-up
					operating properly.
	terminals, and install jumper wire on the speed-up termi-
				9.	Short between the speed-up terminals using a thermostat
	nals.
					screwdriver. This reduces the timing sequence to 1/256 of
7.	Unit changes over to defrost within 90 sec (depending on				original time. (See Fig. 20 and Table 10.)
	timing cycle setting). Liquid-line temperature rises to range			NOTE: Fig. 20 shows timing cycle set at 30 minutes; however,
	where defrost thermostat contacts open. Temperature range			for the CES30110063 board the timing cycle will be set for 90 min
	is from 75°F to 85°F. Resistance goes from zero to ∞ when			and unit initiates defrost within approximately 21 sec. When you
	contacts open.			hear the reversing valve change position, remove screwdriver
8.	If either opening or closing temperature does not fall within			immediately. Otherwise, control will terminate normal 10-minute
	above ranges or thermostat sticks in 1 position, replace			defrost cycle in approximately 2 sec.
	thermostat to ensure proper defrost operation.
					CAUTION: Exercise extreme caution when shorting
CES0110063 DEFROST CONTROL
					speed-up pins. If pins are accidentally shorted to other
Some heat pumps built in 1991 and later incorporate a new defrost
					terminals, damage to the control board will occur.
control. The screw terminals found on the previous control board
have been replaced by a connector plug with stripped-wire leads.
This control board also contains the feature that allows the heat				10.	Unit is now operating in defrost mode. Check between C
pump to restart in defrost if the room thermostat is satisfied during
					and W2 using voltmeter as shown in Fig. 21. Reading on
defrost. The board also contains a 5-minute cycle protector that
					voltmeter should indicate 24v. This step ensures defrost-
prevents the unit from short cycling after it cycles off or after a
					relay contacts have closed, energizing supplemental heat
power interruption. To troubleshoot the board, perform the follow-
					(W2) and reversing valve solenoid (O).
ing items.
				11.	Unit should remain in defrost no longer than 10 minutes.
1. Turn thermostat to OFF. Shut off all power to outdoor unit.
					Actual time in defrost depends on how quickly speed-up
2.	Remove control-box cover for access to electrical compo-
					jumper is removed. If it takes 2 sec. to remove speed-up
	nents and defrost-control board.				jumper after unit has switched to defrost, the unit will
3. Disconnect defrost-thermostat leads from			control board,		switch back to heat mode.
	and connect to ohmmeter. Thermostat leads are the black,			12.	After a few minutes in defrost (cooling) operation, liquid
	insulated wires connected to DFT and R terminals on				line should be warm enough to have caused defrost-
	control board. Resistance reading may be zero (indicating				thermostat contacts to open. Check resistance across defrost
	closed-defrost thermostat), or infinity (∞	for open thermo-			thermostat. Ohmmeter should read infinite resistance, indi-
	stat) depending on outdoor temperature.				cating defrost thermostat has opened at approximately 80°F.
			—19—