GPH16M Service Manual

SERVICING
30
Wiring is subject to change. Always refer to the wiring diagram on the unit for the most up-to-date wiring.
1. Using a voltmeter, check for 230 volts to the motor connec-
tions L and N. If 230 volts is present, proceed to step 2. If
230 volts is not present, check the line voltage circuit to
the motor.
2. Using a voltmeter, check for 24 volts from terminal C to
either terminal 1, 2, 3, 4, or 5, depending on which tap is
being used, at the motor. If voltage present, proceed to
step 3. If no voltage, check 24 volt circuit to motor.
3. If voltage was present in steps 1 and 2, the motor has failed
and will need to be replaced.
Note: When replacing motor, ensure the belly band is between
the vents on the motor and the wiring has the proper drip loop
to prevent condensate from entering the motor.
S-17C UNLOADER TEST PROCEDURE
(2 Stage Compressors Only)
A nominal 24-volt direct current coil activates the internal
unloader solenoid. The input control circuit voltage must be 18
to 28 volt ac. The coil power requirement is 20 VA. The exter-
nal electrical connection is made with a molded plug assem-
bly. This plug contains a full wave rectifier to supply direct
current to the unloader coil.
UNLOADER SOLENOID
(Molded Plug)
Unloader Test Procedure
If it is suspected that the unloader is not working,
the following methods may be used to verify opera-
tion.
1. Operate the system and measure compressor current.
Cycle the unloader 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 volt ac to the unloader molded plug leads
and listen for a click as the solenoid pulls in. Remove power
and listen for another click as the unloader returns to its
original position.
3. If clicks can’t be heard, shut off power and remove the con-
trol circuit molded plug from the compressor and measure
the unloader coil resistance. The resistance should be 32
to 60 ohms, depending on compressor temperature.
4. Next check the molded plug.
A. Voltage check: Apply control voltage to the plug wires
(18 to 28 volt ac). The measured dc voltage at the
female connectors in the plug should be around 15
to 27 vdc.
B. 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 connec-
tors 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 po-
larity on the ohmmeter leads and repeat. The fe-
male connector that read infinity previously should
now read close to zero ohms.
C. Replace plug if either of these test methods doesn’t
show the desired results.
S-17 CHECKING COMPRESSOR WINDINGS
WARNING
HERMETIC COMPRESSOR ELECTRICAL TERMINAL
VENTING CAN BE DANGEROUS. WHEN INSULATING
MATERIAL WHICH SUPPORTS A HERMETIC COM-
PRESSOR OR ELECTRICAL TERMINAL SUDDENLY
DISINTEGRATES DUE TO PHYSICAL ABUSE OR AS A
RESULT OF AN ELECTRICAL SHORT BETWEEN THE
TERMINAL AND THE COMPRESSOR HOUSING, THE
TERMINAL MAY BE EXPELLED, VENTING THE
VAPOR AND LIQUID CONTENTS OF THE COMPRES-
SOR HOUSING AND SYSTEM.
If the compressor terminal PROTECTIVE COVER and gasket
(if required) is not properly in place and secured, there is a
remote possibility if a terminal vents, that the vaporous and
liquid discharge can be ignited, spouting flames several feet,
causing potentially severe or fatal injury to anyone in its path.
This discharge can be ignited external to the compressor if the
terminal cover is not properly in place and if the discharge
impinges on a sufficient heat source.
Ignition of the discharge can also occur at the venting terminal
or inside the compressor, if there is sufficient contaminant air
present in the system and an electrical arc occurs as the ter-
minal vents.
Ignition cannot occur at the venting terminal without the pres-
ence of contaminant air, and cannot occur externally from the
venting terminal without the presence of an external ignition
source.