Sequence Of Operation - Lennox 12CHP060 Installation Instructions Manual

80°F db / 67°F wb
RETURN AIR
MODEL PRESSURE
12CHP−024
12CHP−030
12CHP−036
SUCTION SUCTION
12CHP−042
12CHP−048
12CHP−060
12CHP−024
12CHP−030
12CHP−036
LIQUID LIQUID
12CHP−042
12CHP−048
12CHP−060

Sequence of Operation

Blower Delay − Cooling
When the thermostat is in the cooling mode, the O circuit is
powered which energizes the reversing valve. Upon cool
ing demand, the thermostat closes circuit R and Y. Closing
R and Y closes unit contactor starting compressor and out
door fan. Thermostat automatically closes R to G circuit
which also brings on the indoor blower at the same time.
Upon satisfying cooling demand, thermostat will open
above circuits and open main contactor, stopping com
pressor and outdoor fan.
Blower Delay − Heating
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 in
door blower at the same time. Upon satisfying heating de
mand, the thermostat opens above circuits and stops unit
operation.
Defrost Cycle
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 defrost control is time/
temperature initiated and temperature terminated with a
maximum defrost time (time−out) of 10 minutes. Time be
tween defrost cycles is pre−set at 60 minute intervals at the
factory, but can be field adjusted between 30, 60 or 90 min
utes. See figure 9 for field adjustment of defrost timing.
TABLE 4
NORMAL OPERATING PRESSURES −− COOLING MODE
AIR TEMPERATURE ENTERING OUTDOOR COIL (°F)
65° 70° 75° 80°
78 79 81 82
78 79 81 82
75 77 80 82
80 81 82 84
78 79 80 82
78 79 80 82
140 155 170 184
145 159 173 187
146 161 176 191
155 170 185 200
164 180 196 213
166 182 198 214
82° 85° 90° 95°
83 84 85 87
83 84 85 87
83 84 87 89
84 85 86 87
82 83 84 85
82 83 84 85
190 199 213 228
193 202 216 230
197 206 221 236
206 215 230 245
219 229 245 261
220 229 245 261
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 con
trol will energize the reversing valve solenoid, shifting the
reversing valve and de−energizing the outdoor fan. The de
frost relay will also close energizing tempering heat for in
creased 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.
DEFROST CONTROL TEST AND
TIME PIN LOCATIONS
JUMPER SHOWN ON T2 PIN
DEFROST
TEST PINS
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 defrost system.
Page 9
100° 105° 110°
89 90 92
89 90 92
91 94 96
88 89 90
86 87 88
86 87 88
243 257 272
244 258 273
251 266 281
260 275 290
277 293 309
277 293 308
DEFROST TIME
PINS
T1 = 30 MINUTES
(T1, T2, T3)
T2 = 60 MINUTES
T3 = 90 MINUTES
FIGURE 9
115° 125°
93 96
93 96
98 103
92 94
90 92
90 92
286 316
287 316
296 326
305 335
326 358
324 356