Moisture Contamination; Compressor Contactor - Cornelius XAC 1444 Service Training Manual

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 termi-
nal to a good chassis ground. Compare reading to chart below:
Meter Reading
Meg Ohm
∞
Okay
100
50 to 100 Moisture present
20 to 50 Severe moisture & possible contaminated oil
with acid present
.5 to 20 System has severe contamination
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 saturated and hold large percentages of moisture and the system function without a problem un-
til 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 sys-
tem whenever possible and when it is done to be certain the true problem is correctly diagnosed and re-
paired. Remember, service gauge sets should only be installed after all external checks have been per-
formed.
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:
Check for supply voltage from circuit board, lead connections to contactor coil, and ohms value of coil.
* (3) if the product is 3 phase
NOTE: See compressor run-on condition check procedure on page 36.
TP00952
Compressor Condition Maintenance Required
None needed.
Replace drier.
Replace drier with acid hold type. Run 24
hours, change to regular drier.
Remove compressor oil and refrigerant
charge. Evacuate, install liquid and suction
line driers (acid hold type). Recharge with
new oil and refrigerant. Run 24 hours. Dis
charge system, discard suction line drier,
replace the liquid line drier. Evacuate and
recharge.
32
Xtreme Ice Training Manual
October 17, 2005