Time Delay Control (Tdc); Low Ambient Control (Lac) - Rheem PNL-*AZ Series Installation Instructions Manual

NOTE: The installation of a crankcase heater is recommended if the system charge
exceeds the values in Table 8. All 3-phase models come with a crankcase heater facto-
ry installed.
TABLE 8
MAXIMUM SYSTEM CHARGE VALUES: (-)PNL/(-)PPL
Model
Size*
-018
-024
-030/-031
-036
-042/-043
-048/-049
*-060 comes with the crankcase heater factory-installed.
All heaters are located on the lower half of the compressor shell. Its purpose is to drive
refrigerant from the compressor shell during long off cycles, thus preventing damage to
the compressor during start-up.
At initial start-up or after extended shutdown periods, make sure the heater is energized
for at least 12 hours before the compressor is started. (Disconnect switch on and wall
thermostat off.)

14.2 TIME DELAY CONTROL (TDC)

The time delay (TDC) is in the low voltage control circuit. When the compressor shuts off
due to a power failure or thermostat operation, this control keeps it off at least 5 minutes
which allows the system pressure to equalize, thus not damaging the compressor or
blowing fuses on start-up.
14.3 LOW AMBIENT CONTROL (LAC) – RXAD-A08
This component senses compressor head pressure and shuts the heat pump fan off
when the head pressure drops to approximately 220 PSIG. This allows the unit to build a
sufficient head pressure at lower outdoor ambient (down to 0°F) in order to maintain sys-
tem balance and obtain improved capacity. Low ambient control should be used on all
equipment operated below 70°F ambient.
Compressor
Model Number
ZP16K5E
ZP21K5E
ZP25K5E
ZP34K5E
ZP38K5E
ZP42K5E
Charge Limit
Without
Crankcase Heater*
8.0 lbs.
8.0 lbs.
8.0 lbs.
10.0 lbs.
10.0 lbs.
10.0 lbs.
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