Service Manual

SERVICING
28
S-17A RESISTANCE TEST
Each compressor is equipped with an internal overload.
The line break internal overload senses both motor amperage
and winding temperature. High motor temperature or amper-
age 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
1. Remove the leads from the compressor terminals.
WARNING
SEE WARNINGS S-17 BEFORE REMOVING COMPRES-
SOR 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 compressor.
S-17B GROUND TEST
If fuse, circuit breaker, ground fault protective device, etc., has
tripped, this is a strong indication that an electrical problem
exists and must be found and corrected. The circuit protective
device rating must be checked and its maximum rating should
coincide with that marked on the equipment nameplate.
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 near-
est point to the compressor.
WARNING
DAMAGE CAN OCCUR TO THE GLASS EMBEDDED
TERMINALS IF THE LEADS ARE NOT PROPERLY
REMOVED. THIS CAN RESULT IN TERMINAL AND
HOT OIL DISCHARGING.
HI-POT
COMPRESSOR GROUND TEST
2. Identify the leads and using a Megger, Hi-Potential Ground
Tester, or other suitable instrument which puts out a volt-
age between 300 and 1500 volts, check for a ground sepa-
rately between each of the three leads and ground (such
as an unpainted tube on the compressor). Do not use a
low voltage output instrument such as a volt-ohmmeter.
3. If a ground is indicated, then carefully remove the compres-
sor terminal protective cover and inspect for loose leads or
insulation breaks in the lead wires.
4. If no visual problems indicated, carefully remove the leads
at the compressor terminals.
Carefully retest for ground, directly between compressor
terminals and ground.
5. If ground is indicated, replace the compressor.