Manual 2100-537
I
Page
47 of 54
SERVICE
SERVICE HINTS
1. Caution owner to maintain clean air filters at all times.
Also, not to needlessly close off supply and return air
registers. This reduces airflow through the system,
which shortens equipment service life as well as
increasing operating costs.
2. Check all power fuses or circuit breakers to be sure that
they are the correct rating.
UNBRAZING SYSTEM COMPONENTS
If the refrigerant charge is removed from a scroll equipped
unit by bleeding the high side only, it is sometimes possible
for the scrolls to seal, preventing pressure equalization
through the compressor. This may leave low side shell and
suction line tubing pressurized. If the brazing torch is then
applied to the low side while the low side shell and suction
line contains pressure, the pressurized refrigerant and
oil mixture could ignite when it escapes and contacts the
brazing flame. To prevent this occurrence, it is important
to check both the high and low side with manifold gauges
before unbrazing.
ECM MOTOR
This unit is equipped with an ECM motor. It is important
that the blower motor plugs are not plugged in or unplugged
while the power is on. Failure to remove power prior to
unplugging or plugging in the motor could result in motor
failure.
WARNING
Both the high and low side of the scroll compressor
must be checked with manifold gauges before
unbrazing system components. Failure to do so
could cause pressurized refrigerant and oil mixture
to ignite if it escapes and contacts the brazing flame
causing property damage, bodily harm or death.
COMPRESSOR SOLENOID
(See Sequence of Operation on Pages 37 & 38 for function.)
A nominal 24-volt direct current coil activates the internal
compressor solenoid. The input control circuit voltage must
be 18 to 28 volts ac. The coil power requirement is 20 VA.
The external electrical connection is made with a molded
plug assembly. This plug contains a full wave rectifier to
supply direct current to the unloader coil.
Compressor Solenoid Test Procedure –
If it is suspected
that the unloader is not working, the following methods may
be used to verify operation.
1. Operate the system and measure compressor amperage.
Cycle the compressor solenoid on and off at 10-second
intervals. The compressor amperage should go up or
down at least 25 percent.
2. If step one does not give the expected results, shut unit
off. Apply 18 to 28 volts ac to the solenoid molded
plug leads and listen for a click as the solenoid pulls
in. Remove power and listen for another click as the
solenoid returns to its original position.
3. If clicks can’t be heard, shut off power and remove the
control circuit molded plug from the compressor and
measure the solenoid coil resistance. The resistance
should be 32 to 60 ohms depending on compressor
temperature.
4. Next, check the molded plug.
Voltage check
: Apply control voltage to the plug wires
(18 to 28 volts ac). The measured
dc
voltage at the female
connectors in the plug should be around 15 to 27 vdc.
Resistance check
: Measure the resistance from the end of
one molded plug lead to either of the two female connectors
in the plug. One of the connectors should read close to zero
ohms, while the other should read infinity. Repeat with
other wire. The same female connector as before should
read zero, while the other connector again reads infinity.
Reverse polarity on the ohmmeter leads and repeat. The
female connector that read infinity previously should now
read close to zero ohms.
Replace plug if either of these test methods does not show
the desired results.
CAUTION
Do not plug in or unplug blower motor
connectors while the power is on. Failure
to do so may result in motor failure.
