2.To check the compressor motor for accidental ground, perform a continuity check between terminals C, R and S to the compressor shell or a copper line of the refrigeration system (do not use a painted surface). Continuity present, the compressor windings are grounded and the compressor must be replaced.
If the compressor starts, but trips repeatedly on the overload protector, remember that the overload is both tem- perature and current activated. Be sure to check:
SLow voltage
SUndersized supply lines
SHigh head pressure
SHigh suction pressure
SDefective capacitors
SCompressor mechanical problems
SLow refrigerant charge
LEAK DETECTION
The new
While the instruments for leak detection are different, the processes have not changed. Basics to remember:
1.Look for signs of oil when you visually start your leak check process. Oil is carried with the refrigerant. If the oil has leaked out so will the refrigerant.
2.Refrigerant vapor is heavier than air. When leak checking suspect areas, probe below the joints or connec- tions.
A.Always check the
B.Check the
C.Following a & b will normally allow the highest pressure on each portion of the system for the best detection.
3.Systems short of refrigerant will show improper operational results in both the freeze and harvest cycles. Many systems will appear normal in higher operating temperatures and change drastically in cooler con- denser temperatures.
4.Many new and reworked leak detection instruments have the ability to detect CFC’s, HCFC’s and the new HFC’s by making a simple switch selection. This type of detector will be more sensitive on one setting than the other. This results in finding some leaks that are so small it may take years before the actual leak rate would create adverse operating conditions in the product.
Abubble test and/or additives with UV lamp may be the best team for the most positive leak testing results.
5.Never pressurize a system with oxygen or a mixture of refrigerant and air. Either of these methods may cause a system explosion to occur.
6.Pressurizing systems to leak test should only be done with dry nitrogen. Be sure the regulator setting does not exceed the recommended system pressure.
CAUTION: A full cylinder of nitrogen will have pressure of approximately 2700 PSI.
7.Failure to correct leaks will also cause shorter compressor life as a result of the higher operating tempera- tures. Always leak check the total system as one located leak may not be the only leak.
SYSTEM EVACUATION & RECHARGING
Should service work ever be required on a product where the sealed refrigeration is opened for any reason, the refrigerant must be recovered, drier/filter replaced, evacuated and recharged. The old method of “purging” is NOT ACCEPTABLE. Always evacuate the system through both the high and low side service valves. Be certain both valves are completely open when evacuating and the drier/filter has been replaced.
SELF-CONTAINED PRODUCTS
With the new POE [Polyol Ester] oils, the refrigeration system is more prone to moisture problems than the CFC systems. Every effort should be made to never have the system open to the atmosphere for longer than 15 min- utes, and the replacement of the drier/filter is no longer an option, [IT IS MANDATORY].
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Rev 3/4/96 |
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