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Manual 2100-373
Page 13
START UP
IMPORTANT INSTALLER NOTE
For improved start up performance, wash the indoor
coil with a dish detergent.
CRANKCASE HEATERS
WH241 units are provided with compressor crankcase
heat.
These models have an insertion well-type heater located
in the lower section of the compressor housing. This is
a self-regulating type heater that draws only enough
power to maintain the compressor at a safe temperature.
Some form of crankcase heat is essential to prevent
liquid refrigerant from migrating to the compressor
causing oil pump out on compressor start up and
possible valve failure due to compressing a liquid.
The decal in Figure 9 is affixed to all outdoor units
detailing start up procedure. This is very important.
Please read carefully.
SERVICE HINTS
1. Caution homeowner to maintain clean air filters at
all times. Also, not to needlessly close off supply
and return air registers. This reduces air flow
through the system which shortens equipment
service life as well as increasing operating costs.
2. Switching to heating cycle at 75° F or higher outside
temperature may cause a nuisance trip of the remote
reset high pressure switch. Turn thermostat off,
then on, to reset the high pressure switch..
3. The heat pump wall thermostats perform multiple
functions. Be sure that all function switches are
correctly set for the desired operating mode before
trying to diagnose any reported service problems.
4. Check all power fuses or circuit breakers to be sure
they are the correct rating.
5. Periodic cleaning of the outdoor coil to permit full
and unrestricted airflow circulation is essential.
SEQUENCE OF OPERATION
COOLING – Circuit R-Y makes at thermostat pulling
in compressor contactor, starting the compressor and
outdoor motor. The G (indoor motor) circuit is
automatically completed on any call for cooling
operation or can be energized by manual fan switch on
subbase for constant air circulation.
IMPORTANT
THESE PROCEDURES MUST BE
FOLLOWED AT INITIAL START UP AND
AT ANY TIME POWER HAS BEEN
REMOVED FOR 12 HOURS OR LONGER.
TO PREVENT COMPRESSOR DAMAGE WHICH
MAY RESULT FROM THE PRESENCE OF LIQUID
REFRIGERANT IN THE COMPRESSOR CRANK-
CASE:
1. MAKE CERTAIN THE ROOM THERMOSTAT IS IN
THE “OFF” POSITION. (THE COMPRESSOR IS
NOT TO OPERATE.)
2. APPLY POWER BY CLOSING THE SYSTEM
DISCONNECT SWITCH. THIS ENERGIZES THE
COMPRESSOR HEATER WHICH EVAPORATES
THE LIQUID REFRIGERANT IN THE CRANK-
CASE.
3. ALLOW 4 HOURS OR 60 MINUTES PER POUND
OF REFRIGERANT IN THE SYSTEM AS NOTED
ON THE UNIT RATING PLATE, WHICHEVER IS
GREATER.
4. AFTER PROPERLY ELAPSED TIME THE
THERMOSTAT MAY BE SET TO OPERATE THE
COMPRESSOR.
5. EXCEPT AS REQUIRED FOR SAFETY WHILE
SERVICING — DO NOT OPEN SYSTEM
DISCONNECT SWITCH.
7961-061
FIGURE 9
HEATING – a 24V solenoid coil on reversing valve
controls heating cycle operation. Two thermostat
options, one allowing “Auto” changeover from cycle to
cycle, and the other constantly energizing solenoid coil
during heating season and thus eliminating pressure
equalization noise except during defrost, are to be used.
On “Auto” option, a circuit is completed from R-W1
and R-Y on each heating “ON” cycle energizing
reversing valve solenoid and pulling in compressor
contactor starting compressor and outdoor motor. R-G
also make starting indoor blower motor. Heat Pump
heating cycle now in operation. The second option has
no “Auto” changeover position, but instead energizes
the reversing valve solenoid constantly whenever the
system switch on subbase is placed in “Heat” position,
the “B” terminal being constantly energized from R. A
thermostat demand for heat completes R-Y circuit
pulling in compressor contactor starting compressor and
outdoor motor. R-G also make starting indoor blower
motor.