JOHNSON CONTROLS
65
SECTION 5 – MAINTENANCE
FORM 160.81-NOM1
ISSUE DATE: 10/3/2020
5
MEGOHM THE MOTOR
Make certain that the motor disconnect switch (circuit
breaker) is in the open position. Megohm the motor as
follows:
1. Use a megohm meter to verify the minimum mo-
tor and wiring insulation resistance. Megohm be-
tween phases and each phase to ground, Refer to
, Diagram, Megohm Mo-
tor Windings.
2. If insulation resistance values fall to the left of the
curve, remove external leads from the motor and
repeat test.
Motor is to be megged with the starter at
ambient temperature after 24 hours of
idle standby.
CHECKING SYSTEM FOR LEAKS
Leak Testing During Operation
The refrigerant side of the system is carefully pressure
tested and evacuated at the factory.
After the system is in operation under load, the high
pressure components should be carefully leak tested
with a leak detector to be sure all joints are tight.
If a leak exists, frequent purging will be required or
refrigerant will be lost.
If any leaks are indicated, they must be repaired im-
mediately. Usually, leaks can be stopped by tightening
flare nuts or flange bolts. However, if it is necessary to
repair a welded joint, the refrigerant charge must be re-
moved. (See the
Handling Refrigerant for Dismantling
Conducting R-134a Pressure Test
With the R-134a charge removed and all known leaks
repaired, the system should be charged with a small
amount of R-134a mixed with dry nitrogen so that a
halide torch or electronic leak detector can be used to
detect any leaks too small to be found by the soap test.
To test with R-134a, proceed as follows:
1. With no pressure in the system, charge R-134a
gas and dry nitrogen into the system through the
charging valve to a pressure of 150 PSIG.
2. To be sure that the concentration of refrigerant has
reached all parts of the system, slightly open the
oil charging valve and test for the presence of re-
frigerant with a leak detector.
3. Test around each joint and factory weld. It is im-
portant that this test be thoroughly and carefully
done, spending as much time as necessary and us-
ing a good leak detector.
4. To check for refrigerant leaks in the evaporator
and condenser, open the vents in the evaporator
and condenser heads and test for the presence of
refrigerant. If no refrigerant is present, the tubes
LD00475
FIGURE 26 -
DIAGRAM, MEGOHM MOTOR WINDINGS
