Schreiber Chillers Old 4 ton MRI User Manual
Page 24
WARNING
Overcharging a refrigeration or air conditioning system can be dangerous.
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If a system refrigerant overcharge 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 which 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 recommended by the manufacturer of the refrigeration, air
conditioning, or heat pump system.
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