Cornelius I Series Spezifikationen PDF herunterladen (Seite 31)

TP00952

November 26, 200126

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

MegĆOhm

Compressor Condition Maintenance Required

100 Ć ∞

Okay None needed.

50 to 100 Moisture present Replace drier.

20 to 50 Severe moisture & possible contaminated oil

with acid present

Replace drier with acid hold type. Run 24

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 refrigerant. Run 24 hours. DisĆ

charge system, discard 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 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 30.

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