Cornelius CR1400, IAC 322, CR800 Service Stem Valves, Moisture Contamination, Compressor Contactor

SERVICE STEM VALVES

When closing the service stem valves to remove your gauge and manifold set always close the high side stem valve first. Following this procedure will allow the system to “PULL” the refrigerant vapor from your manifold set to reduce refrigerant loss. When the pressure has been reduced, close the low side stem valve.

MOISTURE CONTAMINATION

With the major changes in refrigerants in today’s marketplace and the use of hydroscopic oils the control of moisture and contaminates have become more critical to safeguard against than ever before in the history of mechanical refrigeration.

Contaminates are also the most difficult of all problems to determine. A Meg-Ohm meter “Megger” can be a valuable tool to aid in the analysis of this problem. A Meg-Ohm reading log may be started any time after 90 days of operation of the product. To perform the test, proceed as listed.

Disconnect all three (3) compressor leads, take a Meg-Ohm meter reading from each compressor terminal to a good chassis ground. Compare reading to chart below:

Meter Reading	Compressor Condition	Maintenance Required
Meg8Ohm
100 8 ∞	Okay	None needed.
50 to 100	Moisture present	Replace drier.
20 to 50	Severe moisture & possible contaminated oil	Replace drier with acid hold type. Run 24
	with acid present	hours, change to regular drier.
.5 to 20	System has severe contamination	Remove compressor oil and refrigerant charge.
		Evacuate, install liquid and suction line driers

(acid hold type). Recharge with new oil and re8 frigerant. Run 24 hours. Discharge system, dis8 card suction line drier, replace the liquid line drier. Evacuate and recharge.

Readings in the range listed below 100 Meg-Ohm would be an indicator that the system being tested may have a contamination problem. Where does the problem come from? As an example, the filter drier may become sat- urated and hold large percentages of moisture and the system function without a problem until such time as the product operating conditions change. Should the room temperature increase, or the condenser plug-up etc., the higher operating pressures and temperatures may cause the drier filter to release a portion of it’s held moisture. It is also imperative to avoid opening the sealed refrigeration system whenever possible and when it is done to be certain the true problem is correctly diagnosed and repaired. Remember, service gauge sets should only be installed after all external checks have been performed.

CAUTION: Megger checks should NEVER be performed on any compressor that is under a vacuum.

COMPRESSOR CONTACTOR

The contactor serves as the voltage supply switch for the compressor circuit. Voltage to the coil of the contactor is supplied by the circuit board.

Check Out:

The two (2)* line supply screws of the contactor should always have supply voltage present when voltage is on to the product.

The other two (2)* screws (load) should have line voltage when the contactor is energized. The contactor coil receives its supply voltage from the circuit board. Should the contactor fail to energize:

12/1/94	27	166240004
Rev 3/4/96