3DJH
Crankcase Heater
,03257$17
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Thermostat Operation
Some heat pump thermostats incorporate isolating
contacts and an emergency heat function (which in-
cludes an amber indicating light). The thermostat is
not included with the unit and must be purchased
separately.
Emergency Heat Function
An emergency heat function is designed into some ther-
mostats. This feature is applicable when isolation of
outdoor unit is required or when auxiliary electric heat is
staged by outdoor thermostats. When the room ther-
mostat is placed in the emergency heat position, the
outdoor unit control circuit is isolated from power and
field-provided relays bypass the outdoor thermostats.
An amber indicating light simultaneously comes on to
remind the homeowner that he is operating in the emer-
gency heat mode.
Emergency heat is usually used during a heat pump
shutdown, but it should also be used following a pow-
er outage if power has been off for over an hour and
the outdoor temperature is below 50EF (10EC). Sys-
tem should be left in the emergency heat mode at
least six hours to allow the crankcase heater sufficient
time to prevent compressor slugging.
Defrost System
The HP23 defrost system includes two components:
a defrost thermostat, and a defrost timer.
Defrost Thermostat
The defrost thermostat is mounted on the liquid line
between the check valve/drier and the distribu-
tor.When defrost thermostat senses 35EF (2EC) or
cooler, its contacts close and send a signal to the de-
frost timer for it to start the timing. It also terminates
defrost when the liquid line warms up to 70EF (21EC).
Defrost Timer
This control asks for a defrost every 60 minutes after the
defrost thermostat closes. The timer will not allow a de-
frost to last for more than 14 minutes. The defrost timer
can be field adjusted from a 60--minute to a 30-- or
90--minute defrost interval if warranted by climatic con-
ditions.
Timed Off Control
(International Units ONLY)
Five ton single phase units are factory equipped with
a timed off control which provides low voltage
protection and prevents compressor short cycling.
High Pressure Switch
(International Units ONLY)
The HP23 is factory--equipped with a manual reset
high pressure switch which is mounted on a valve
core in the line to allow for easy replacement.
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At the beginning of each heating or cooling season,
the system should be cleaned as follows:
Heat Pump Unit
1- Clean and inspect outdoor coil (may be flushed
with a water hose).
2- Outdoor unit fan motor is pre--lubricated and
sealed. Always relubricate motor according to
the instructions on the motor manufacturers
nameplate.
3- Visually inspect all connecting lines, joints and
coils for evidence of oil leaks.
4- Check all wiring for loose connections.
5- Check for correct voltage at unit (unit operating).
6- Check amp draw on heat pump fan motor.
Unit nameplate__________Actual__________.
7- Inspect drain holes in coil compartment base and
clean if necessary.
NOTE-If insufficient heating or cooling occurs, the
unit should be gauged and refrigerant charge should
be checked.
Indoor Coil
1- Clean coil if necessary.
2- Check connecting lines, joints and coil for evi-
dence of oil leaks.
3- Check condensate line and clean if necessary.
Indoor Unit
1- Clean or change filters.
2- Lennox blower motors are pre--lubricated and per-
manently sealed. No further lubrication is neces-
sary.
3- Adjust blower speed for cooling. The pressure
drop over the coil should be checked to determine
the correct blower CFM. Refer to the Lennox
Cooling Service Handbook for pressure drop
tables and procedures.
4- Check all wiring for loose connections.
5- Check for correct voltage at unit.
6- Check amp draw on blower motor.
Motor nameplate__________Actual__________.
