Service Manual

SERVICING
102
S-17ARESISTANCE 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 amperage
heats the disc causing it to open, breaking the common circuit
within the compressor on single phase units.
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.
Fuse, circuit breaker, ground fault protective device, etc. has not
tripped -
WARNING
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
1. Remove the leads from the compressor terminals.
WARNING
Herm etic compressor electrical terminal venting can
be dangerous. When insulating material which
supp
orts a hermetic compressor 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
compressor housing and system.
2. Using an ohmmeter, test continuity between terminals S-R, C-
R, and C-S, on single phase units or terminals T2, T2 and T3,
on 3 phase units.
S
R
C
COMP
OHMMETER
TESTING COMPRESSOR WINDINGS
If either winding does not test continuous, replace the compres-
sor.
NOTE: If an open compressor is indicated, allow ample time for
the internal overload to reset before replacing compressor.
S-17BGROUND 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 nearest
point to the compressor.
2. Identify the leads and using an ohmmeter on the R x 10,000
scale or the highest resistance scale on your ohmmeter check
the resistance between each of the three leads separately to
ground (such as an unpainted tube on the compressor).
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.
5. Carefully retest for ground, directly between compressor
terminals and ground.
6. If ground is indicated, replace the compressor. The resistance
reading should be infinity. If there is any reading on meter,
there is some continuity to ground and compressor should
be considered defective.
OHMMETER
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.
S-17CUNLOADER TEST PROCEDURE
A nominal 24-volt direct current coil activates the internal
unloader solenoid. The input control circuit voltage must be 18