
SERVICING
45
S-17 CHECKING COMPRESSOR WINDINGS
WARNING
H
ERMETIC COMPRESSOR ELECTRICAL TERMINAL VENTING CAN BE DANGER-
OUS.
W
HEN INSULATING MATERIAL, WHICH SUPPORTS A HERMETIC
COMPRESSOR 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 VAPOROUS AND LIQUID CONTENTS OF THE
COMPRESSOR HOUSING AND SYSTEM.
If the compressor terminal PROTECTIVE COVER and gas-
ket (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 termi-
nal or inside the compressor, if there is sufficient contami-
nant air present in the system and an electrical arc occurs
as the terminal 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 igni-
tion source.
Therefore, proper evacuation of a hermetic system is essen-
tial at the time of manufacture and during servicing.
To reduce the possibility of external ignition, all open flame,
electrical power, and other heat sources should be extin-
guished or turned off prior to servicing a system.
If the following test indicates shorted, grounded or open wind-
ings, see procedures S-19 for the next steps to be taken.
S-17A Resistance Test
Each compressor is equipped with an internal overload.
The line break internal overload senses both motor amper-
age and winding temperature. High motor temperature or
amperage heats the disc causing it to open, breaking the
common circuit within the compressor on single phase units.
The three phase internal overload will open all three legs.
Heat generated within the compressor shell, usually due to
recycling of the motor, high amperage or insufficient gas to
cool the motor, is slow to dissipate, allow at least three to
four hours for it to cool and reset, then retest.
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove the leads from the compressor terminals.
WARNING
S
EE WARNINGS S-17 BEFORE REMOVING COMPRESSOR TERMINAL COVER.
2. Using an ohmmeter, test continuity between terminals
S-R, C-R, and C-S, on single phase units or terminals
T1, T2 and T3, on 3 phase units.
S
R
C
COMP
OHMMETER
TESTING COMPRESSOR WINDINGS
If either winding does not test continuous, replace the com-
pressor.
NOTE:
If an open compressor is indicated allow ample time
for the internal overload to reset before replacing compres-
sor.
S-17B Ground Test
If fuse, circuit breaker, ground fault protective device, etc.,
has tripped, this is a strong indication that an electrical prob-
lem exists and must be found and corrected. The circuit pro-
tective device rating must be checked and its maximum rat-
ing should coincide with that marked on the equipment name-
plate.
With the terminal protective cover in place, it is acceptable to
replace the fuse or reset the circuit breaker ONE TIME ONLY
to see if it was just a nuisance opening. If it opens again, DO
NOT continue to reset.
Disconnect all power to unit, making sure that all power legs
are open.
1. DO NOT remove protective terminal cover. Disconnect
the three leads going to the compressor terminals at the
nearest point to the compressor.