Service manual

SERVICING
31
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 sev-
eral feet, causing potentially severe or fatal injury to any-
one in its path.
This discharge can be ignited external to the compressor if
the terminal cover is not properly in place and if the dis-
charge impinges on a sufficient heat source.
Ignition of the discharge can also occur at the venting ter-
minal or inside the compressor, if there is sufficient con-
taminant air present in the system and an electrical arc
occurs as the terminal vents.
Ignition cannot occur at the venting terminal without the
presence of contaminant air, and cannot occur externally
from the venting terminal without the presence of an exter-
nal ignition source.
Therefore, proper evacuation of a hermetic system is es-
sential 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
windings, 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
Disconnect Electrical Power Supply:
1. Remove the leads from the compressor terminals.
WARNING
SEE WARNING S-17 PAGE 66 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
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 com-
pressor.
NOTE: If an open compressor is indicated allow ample
time for the internal overload to reset before replacing com-
pressor.
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
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.
WARNING
DAMAGE CAN OCCUR TO THE GLASS EMBEDDED
TERMINALS AT THIS POINT IF THE LEADS ARE NOT
PROPERLY REMOVED, WHICH CAN RESULT IN THE
TERMINAL VENTING AND HOT OIL DISCHARGING.
HI-POT
COMPRESSOR GROUND TEST