Schreiber Chillers Modular Chillers - Manual (Page 30)

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Ignition of the discharge can also occur at the venting terminal or inside the motor-compressor enclosure, if
there is sufficient contaminant 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 external ignition source.
It is, therefore, essential that any air in a refrigeration, air conditioning, or heat pump system be completely
removed when the system is manufactured – when the system is installed – and whenever the system is field
processed a result of field service. Field service includes, but is not limited to, leak repairs or compressor
replacement.
Eliminating air within the system prevents ignition at, or in, the hermetic compressor if a terminal should vent,
thereby reducing the hazard potential.
To reduce the possibility of external ignition, all open flame, electrical power, and other heat sources should be
extinguished or turned off prior to servicing a system.
Before using a soldering or welding torch to remove or repair tubing, make sure all the system refrigerant charge
has safely been released
A venting terminal presents no danger to servicing personnel or anyone else in the vicinity if the compressor
terminal PROTECTIVE COVER is properly in place as shown on Tecumseh Products Company drawings and
diagrams using the parts as shown on Tecumseh Products Company bills of material.
Hermetic compressors can be properly serviced without unnecessarily removing the terminal PROTECTIVE
COVER by adhering to the following service procedures:
1. If the branch circuit, short circuit, and ground fault protective device, i.e., fuse or the circuit breaker is
open, this is a strong indication that an electrical problem exists and must be found and corrected.
The circuit protective device rating must first be checked as required by the National
Electrical Code, and its maximum rating should coincide with that marked on the
equipment nameplate and/or on the unit wiring diagram and/or instructions. This beaker
or fuse rating should be as low as practical. A rule of thumb is 175% times the motor-
compressor RLA (FLA on older units) as shown on the unit nameplate.
It is acceptable to first replace the fuse or reset the circuit breaker ONE TIME to determine if it was just
a nuisance opening. WARNING! The terminal PROTECTIVE COVER must be securely in place.
2. If the fuse or circuit breaker again opens, DO NOT continue to replace or reset, as the equipment
obviously has an electrical problem. CAUTION! Continual resetting may cause the terminal to vent.
3. DISCONNECT all power to the unit, making sure all power legs are open.
4. Without removing the terminal PROTECTIVE COVER, disconnect the three leads going to the
compressor terminals at the nearest point to the compressor, and identify them as Common (C), Start
(S), and Run (R). Identification can generally be made through the unit- wiring diagram. DO NOT
disconnect at the compressor terminals at this time.
5. With a Megger, Hi-Potential Ground Tester, or other suitable instruments which puts out a voltage
between 300 and 1500 volts, check for a ground separately between each of the three C, S, & R leads
and ground (such as an unpaired tube on the compressor). Do not use a low voltage output instrument
such as a volt-ohmmeter or other such continuity instruments, as these will not detect a low level fault
(ground).
6. If a ground is indicated, then carefully remove the compressor terminal ROTECTIVE COVER and
inspect for loose leads or insulating breaks in the lead wires.