JOHNSON CONTROLS
28
FORM 160.76-O1
ISSUE DATE: 6/15/2015
SECTION 6 - MAINTENANCE
inder must be admitted to the system pressure until the
system pressure is raised above the point correspond-
ing to the freezing point of the evaporator liquid. For
water, the pressure corresponding to the freezing point
is 8.54 PSIG (58.9 kPa) for R-134a (at sea level).
While charging, every precaution must be taken to pre-
vent moisture laden air from entering the system. Make
up a suitable charging connection from new copper tub-
ing to fit between the system charging valve and the fit-
ting on the charging drum. This connection should be
as short as possible but long enough to permit sufficient
flexibility for changing drums. The charging connection
should be purged each time a full container of refriger-
ant is connected and changing containers should be done
as quickly as possible to minimize the loss of refrigerant.
Refrigerant may be furnished in cylinders containing
either 30, 50, 125, 1,025 or 1750 lbs. (13.6, 22.6, 56.6,
464 or 794 kg) of refrigerant.
The nameplate on the chiller contains the
correct refrigerant charge information
for the chiller.
CHECKING THE REFRIGERANT CHARGE
DURING UNIT SHUTDOWN
The refrigerant charge is specified for each chiller model.
Charge the correct amount of refrigerant and record the
level in the evaporator sight glass.
The refrigerant charge should always be checked and
trimmed when the system is shut down.
The refrigerant charge level must be checked after the
pressure and temperature have equalized between the
condenser and evaporator. This would be expected to be
4 hours or more after the compressor and water pumps
are stopped. The level should visible in the sight glass.
Charge the refrigerant in accordance with the meth-
od shown under the REFRIGERANT CHARGING,
above. The refrigerant level should be observed and
the level recorded after initial charging.
HANDLING REFRIGERANT FOR DISMANTLING
AND REPAIRS
If it becomes necessary to open any part of the refriger-
ant system for repairs, it will be necessary to remove
the charge before opening any part of the unit. If the
chiller is equipped with optional valves, the refrigerant
can be isolated in either the condenser or evaporator /
compressor while making any necessary repairs.
MEGGING THE MOTOR
While the main disconnect switch and compressor mo-
tor starter are open, meg the motor as follows:
1. Using a megohm meter (megger), meg between
phases and each phase to ground (Refer to
); these readings are to be interpreted
2. If readings fall below shaded area, remove exter-
nal leads from motor and repeat test.
Motor is to be megged with the starter at
ambient temperature after 24 hours of
idle standby.
FIGURE 14 -
DIAGRAM, MEGGING MOTOR WINDINGS
LD00475
MAIN DISCONNECT
(OPEN)
STARTER (OPEN)
MEGOHM METER
MEGOHM EACH
WINDING TO GROUND
MEGOHM
METER
MEGOHM
BETWEEN
WINDINGS
