Maintenance - Lennox HP21 Series Installation Instructions Manual

DEFROST CONTROL
C C W Y
Yout
CC
RV
C
TERMINATION
TEMPERATURE
PINS
SENSOR
CONNECTIONS
Figure 17
Operation
When the reversing valve is de−energized, the Y1 circuit is
energized, and the coil temperature is below 35°F (2°C),
the board logs the compressor run time. When the unit is
initially started and the control is not calibrated, a defrost
cycle will be initiated after 34 minutes of heating mode com-
pressor run time. The control will terminate the defrost
cycle when the coil temperature rises above the preset ter-
mination temperature or after 14 minutes of defrost opera-
tion. The termination temperature is factory set at 70°F.
This setting may be adjusted in the field to 50°F (10°C),
60°F (16°C), 70°F (21°C), or 80°F (27°C). The control will
attempt to self−calibrate after this (and all other) defrost
cycle(s). Calibration success depends on stable system
temperatures during the 20−minute calibration period. If the
board fails to calibrate, another defrost cycle will be initi-
ated after 34 minutes of heating mode compressor run
time. Once the defrost board is calibrated, it will use de-
mand defrost logic to initiate a defrost cycle. A demand de-
frost system initiates defrost when the difference between
the clear coil and frosted coil temperatures exceeds the
maximum difference allowed by the control.
If the control determines an ambient temperature sensor
failure and the coil temperature is 35°F (2°C) or lower, the
control will repeatedly initiate a defrost cycle after 34 min-
utes of heating mode compressor run time. If the control
determines that the coil temperature sensor has failed, the
control will not initiate a defrost cycle.
O R R
TEST
PINS
AMB
COIL
When Y1 is energized and 24V power is being applied to
the board, a test cycle (approximately 12 seconds) can be
initiated by placing the termination temperature jumper
across the Test" pins. If the jumper is applied to the test
pins before power is applied, or if the jumper is left across
the Test" pins longer than 5 minutes, the control will ignore
the test jumper and will revert to normal operation. The test
jumper will initiate continuous defrost cycles until the test
jumper is removed or the 5−minute test period ends.

Maintenance

Electric shock hazard. Can cause inju-
ry or death. Before attempting to per-
form any service or maintenance, turn
the electrical power to unit OFF at dis-
connect switch(es). Unit may have
multiple power supplies.
Maintenance and service must be performed by a qualified
installer or service agency. At the beginning of each cooling
or heating season, the system should be checked as fol-
lows:
1 − Clean and inspect the outdoor coil. The coil may be
flushed with a water hose. Ensure the power is turned
off before you clean the coil.
2 − Condenser fan motor is prelubricated and sealed. No
further lubrication is needed.
3 − Visually inspect connecting lines and coils for evidence
of oil leaks.
4 − Check wiring for loose connections.
5 − Check for correct voltage at unit (unit operating).
6 − Check amp−draw condenser fan motor.
Unit nameplate _________ Actual ____________ .
NOTE − If owner complains of insufficient cooling, the
unit should be gauged and refrigerant charge checked.
Refer to section on refrigerant charging in this instruc-
tion.
Evaporator Coil
1 − If necessary, clean the coil.
2 − Check connecting lines and coils for evidence of oil
leaks.
3 − Check condensate line and clean, if necessary.
Page 21
Test Mode
WARNING