Carrier 38BYG User Manual
Page 7
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.
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.
Fig. 10—Defrost Control
Table 3—Defrost Control Speedup-
Timing Sequence
PARAMETER
MINIMUM
(MINUTES)
MAXIMUM
(MINUTES)
SPEEDUP
(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
A91444
OF1
OF2
O
R
T2
Y
TI DFT
C
TEST 30 50 90
W1
O
R
W2
Y
C
CES0110063,
CES0130024
Table 4—Required Liquid-Line Temperature (°F)
LIQUID
PRESSURE AT
SERVICE VALVE
(PSIG)
REQUIRED SUBCOOLING
TEMPERATURE (°F)
5
10
15
20
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
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