Page 8
TABLE 4
NORMAL OPERATING PRESSURES ---- COOLING MODE
80qF db / 87qF wb RETURN AIR
AIR TEMPERATURE ENTERING OUTDOOR COIL (qF)
MODEL
PRESSURE
65q
70q
75q
80q
82q
85q
90q
95q
100q
105q
110q
115q
CHP29--024
68
70
75
78
81
82
84
86
89
91
94
96
CHP29--030
68
70
74
78
80
80
81
82
84
87
89
91
CHP29--036
SUCTION
64
70
75
81
83
84
85
87
90
93
95
98
CHP29--042
SUCTION
69
73
76
80
81
82
83
85
88
91
93
96
CHP29--048
74
77
79
80
81
82
82
84
84
85
86
87
CHP29--060
72
74
75
78
80
81
83
84
85
86
88
90
CHP29--024
182
198
216
233
240
249
265
280
297
314
331
348
CHP29--030
172
190
208
227
234
242
255
268
288
304
321
339
CHP29--036
LIQUID
189
205
221
238
244
253
269
283
304
325
346
367
CHP29--042
LIQUID
195
210
226
241
247
257
274
291
311
331
360
370
CHP29--048
183
211
231
239
244
252
265
287
302
324
345
361
CHP29--060
171
183
195
211
223
239
251
264
281
298
318
333
6(48(1&( 2) 23(5$7,21
&RROLQJ
When the thermostat is in the cooling mode, the O cir-
cuit is powered which energizes the reversing valve.
Upon cooling demand, the thermostat closes circuit R
and Y. Closing R and Y closes unit contactor starting
compressor and outdoor fan. Thermostat automatical-
ly closes R to G circuit which also brings on the indoor
blower at the same time. Upon satisfying cooling de-
mand, thermostat will open above circuits and open
main contactor, stopping compressor and outdoor fan.
If unit is equipped with a delay timer, the blower will
continue to operate for 90 seconds which improves
system efficiency.
+HDWLQJ
Upon heating demand the thermostat closes circuit R
to Y, closing unit contactor, starting compressor and
outdoor fan. The reversing valve is not energized in the
heating mode. The thermostat again automatically
brings on the indoor blower at the same time. Upon
satisfying heating demand, the thermostat opens
above circuits and stops unit operation.
'HIURVW &\FOH
If outdoor ambient conditions are such that frost forms
on the outdoor coil, the defrost control monitors the
need for and initiates and terminates defrost cycles as
necessary to maintain system performance. The de-
frost control is time/temperature initiated and temper-
ature terminated with a maximum defrost time (time--
out) of 10 minutes. Time between defrost cycles is
pre--set at 60 minute intervals at the factory, but can be
field adjusted between 30, 60 or 90 minutes. See figure
8 for field adjustment of defrost timing.
T1
T2
T3
DEFROST
TEST PINS
DEFROST TIME PINS
(T1, T2, T3)
JUMPER SHOWN ON T2 PIN
DEFROST CONTROL TEST AND
TIME PIN LOCATIONS
T1 = 30 MINUTES
T2 = 60 MINUTES
T3 = 90 MINUTES
FIGURE 8
The defrost control will initiate a defrost cycle if time
period has elapsed and the defrost sensor detects a
temperature below freezing. At the start of defrost
cycle, the defrost control will energize the reversing
valve solenoid, shifting the reversing valve and de--en-
ergizing the outdoor fan. The defrost relay will also
close energizing tempering heat for increased comfort
during defrost , if the unit is so equipped. The unit will
remain in the defrost mode until the defrost sensor has
determined that the frost has been removed from the
coil or a 10 minute time period has elapsed.
The defrost control is also equipped with a set of test
pins to aid in troubleshooting of the defrost system.
The following is a brief outline of the testing of the de-
frost system.
