Schreiber Chillers 15MEDAC email - Manual (Page 50)

WARNING
Overcharging a refrigeration of air conditioning system can be dangerous
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If a refrigeration system is overcharged and that it is sufficient to immerse the major parts of the motor
and compressor in liquid refrigerant, a situation has been created which, when followed by unusual
circumstances can lead to compressor housing seam separation or rupture.
The sequence of circumstances that can lead to compressor housing seam separation or rupture may
occur in the following manner:
(a) The system overcharge immerses the compressor motor, piston, connecting rods, cylinder, etc, in
liquid refrigerant, thereby effectively forming a hydraulic block preventing the compressor from
starting. This condition is known as locked rotor.
(b) Electric current continues to flow through the compressor motor windings that become, in effect,
electric resistance heaters. The heat produced begins to vaporize the excessive refrigerant liquid
overcharge, causing a rapid increase in system pressure.
(c) If the system compressor protective devices fail for any reason prior to or during this locked rotor
heating cycle, or cycles, liquid refrigerant may be vaporized sufficiently fast enough to raise the
pressure within the system to extremes far in excess of the housing or weld seam design limits.
(d) In some instances where the amount of refrigerant overcharge is critical in proportion to the
system internal volume, the pressure reached can cause a compressor housing seam separation
or rupture, which can be hazardous.
The remedy to eliminate this exceedingly rare but potential hazard is to use correct refrigerant charging
amounts and techniques.
Tecumseh Products Company urges that all individuals responsible for training, teaching, or advising
installation mechanics and service personnel, must emphasize proper charging techniques and strict
adherence to limiting refrigerant charge amounts to those specifically recommend by the manufacturer of
the refrigeration, air conditioning, or heat pump system.
SERVICE BULLETIN
HERMETIC COMPRESSOR ELECTRICAL TERMINAL VENTING CAN BE DANGEROUS
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When the 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 hermetic compressor terminal PROTECTIVE COVER is not properly in place with its
weatherproofing gasket (if required) and bale strap fastening device 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.
The discharge from a venting terminal can be ignited external to the compressor if the terminal
PROTECTIVE COVER is not properly in place and if the discharge impinges on a sufficient heat source
such as, but not limited to, an open flame, electric heater, or an electric spark.
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.