Johnson Controls York YKEP, Operation And Maintenance

Page: 26 / 34

FORM 160.77-O1
ISSUE DATE: 10/22/2020
JOHNSON CONTROLS
26
SECTION 3 - MAINTENANCE
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 the evapora-
tor / compressor while making any necessary repairs.
MEGGING THE MOTOR
While the compressor motor leads are lifted at the lugs
in the drive, meg the motor as follows:
1. Using a megohm meter (megger), meg between
phases and each phase to ground (refer to Figure
12 on Page 26
). These readings can be inter-
preted using the graph shown in
Figure 13 on
Page 27 .
2. If readings fall below the shaded area, remove ex-
ternal leads from motor and repeat the test.
The motor is to be megged with the starter
at ambient temperature after 24 hours of
idle standby with no water flow through
the unit.
The unit must be at positive pressure (no
vacuum) during the megging procedure.
CONDENSERS AND EVAPORATORS
Maintenance of condenser and evaporator shells is im-
portant to provide trouble free operation of the chiller.
The water side of the tubes in the shell must be kept
clean and free from scale. Proper maintenance such as
tube cleaning, and testing for leaks, is covered on the
following pages.
Chemical Water Treatment
The mineral content of the water circulated through
evaporators and condensers varies with almost every
source of supply. Water containing excess amounts of
minerals may corrode the tubes or deposit heat resistant
scale in them. Reliable water treatment companies are
available in most larger cities to supply a water treat-
ing process which will greatly reduce the corrosive and
scale forming properties of almost any type of water.
As a preventive measure against scale and corrosion,
and to prolong the life of evaporator and condenser
tubes, a chemical analysis of the water should be made
preferably before the system is installed. A reliable wa-
ter treatment company can be consulted to determine
whether water treatment is necessary, and if so, to fur-
nish the proper treatment for the particular water con-
dition.
FIGURE 12 - MEGGING MOTOR WINDINGS
LD00475