Carrier 38BYG, 38BYC Defrost Control Speedup Timing Sequence, Required Liquid-Line Temperature F

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

A91444

Table 3—Defrost Control Speedup-

Timing Sequence

PARAMETER	MINIMUM	MAXIMUM	SPEEDUP
	(MINUTES)	(MINUTES)	(NOMINAL)
30–minute cycle	27	33	7 sec
50–minute cycle	45	55	12 sec
90–minute cycle	81	99	21 sec
10–minute cycle	9	11	2 sec
5 minutes	4.5	5.5	1 sec

Fig. 10—Defrost Control

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

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 80°F coil temperature of liquid line.

8.Turn off power to outdoor unit and reconnect fan motor lead to OF2 on control board. (See Fig. 10.)

Step 14—Check Charge

Factory charge is shown on unit rating plate. To check charge in cooling mode, refer to Cooling Only Procedure. To check charge in heating mode, refer to Heating Check Chart Procedure.

COOLING-ONLY PROCEDURE

NOTE: If superheat- or subcooling-charging conditions are not favorable, charge must be weighed in accordance with unit rating plate ± 0.6 oz/ft of 3/8-in. liquid line above or below 15 ft respectively.

EXAMPLE:

To calculate additional charge required for a 25–ft line set:

25 ft – 15 ft = 10 ft X 0.6 oz/ft = 6 oz of additional charge

Units installed with cooling mode TXV require charging with the subcooling method.

1.Operate unit a minimum of 10 minutes before checking charge.

2.Measure liquid service-valve pressure by attaching an accurate gage to service port.

3.Measure liquid-line temperature by attaching an accurate thermistor type or electronic thermometer to liquid line near outdoor coil.

4.Refer to unit rating plate for required subcooling temperature.

5.Refer to Table 4. Find the point where required subcooling temperature intersects measured liquid service-valve pressure.

6.To obtain required subcooling temperature at a specific liquid-line pressure, add refrigerant if liquid-line temperature is higher than indicated or reclaim refrigerant if temperature is lower. Allow a tolerance of ± 3°F.

Table 4—Required Liquid-Line Temperature (°F)

LIQUID		REQUIRED SUBCOOLING
PRESSURE AT			TEMPERATURE (°F)
SERVICE VALVE
	5		10	15	20
(PSIG)
134	71		66	61	56
141	74		69	64	59
148	77		72	67	62
156	80		75	70	65
163	83		78	73	68
171	86		81	76	71
179	89		84	79	74
187	92		87	82	77
196	95		90	85	80
205	98		93	88	83
214	101		96	91	86
223	104		99	94	89
233	107		102	97	92
243	110		105	100	95
253	113		108	103	98
264	116		111	106	101
274	119		114	109	104
285	122		117	112	107
297	125		120	115	110
309	128		123	118	113
321	131		126	121	116
331	134		129	124	119
346	137		132	127	122
359	140		135	130	125

HEATING CHECK CHART PROCEDURE

To check system operation during heating cycle, refer to the Heating Check Chart on outdoor unit. This chart indicates whether a correct relationship exists between system operating pressure and air temperature entering indoor and outdoor units. If pressure and temperature do not match on chart, system refrigerant charge may not be correct. Do not use chart to adjust refrigerant charge.

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