Section 3 Refrigeration Overview; Checking For Proper Operation; Refrigeration Cycle - York MILLENNIUM Manual

SECTION 3 – REFRIGERATION OVERVIEW

CHECKING FOR PROPER OPERATION

Recognition of normal and abnormal trends in system
pressures, temperatures, motor current percentage, and
slide valve position can help ensure reliable operation
and avoid costly equipment down time. The RCC op-
tion allows owners/operators/maintenance to easily
monitor the system data and spot these trends. When
abnormalities are suspected, easy access to system data
can help identify the root cause of the problem and
speed the repair process.
Maintaining a record of system data unique to your
chiller on a weekly basis, or even a daily basis on criti-
cal applications, is recommended. A form is provided
on page 15 that can be copied and used for data re-
cording. Records should be kept in a secure binder.
Normal readings taken under several various ambient
and load conditions should be identified and marked
as a baseline reference. These can then be used for com-
parison and trend spotting purposes.
A printer can also be used for maintaining records. Hand
written entries should be made on the printouts to help
identify particular variables and trends of interest.
A better understanding of the system data provided by
the RCC can be had when the refrigeration cycle is
understood. A review of the cycle is provided.

REFRIGERATION CYCLE

The refrigeration cycle description that follows can be
traced on the refrigerant flow diagram, Figure 4, page
13, for an R-22 YCAS F water chiller.
The refrigerant 'change of state,' as it changes from
liquid to vapor, then back to liquid, is the key compo-
nent in this heat transfer process. How is this accom-
plished? A simplified answer is given.
YORK INTERNATIONAL
The mechanics of a typical refrigerating machine in-
clude these four main components.
A. Evaporator
B. Compressor
C. Condenser
D. Expansion Valve
These components have the following basic functions:
A. In the evaporator, cold refrigerant travels through
hundreds of copper tubes. Water passes over the
cold outer surface of these tubes, thus chilling the
water.
B. The compressor acts like a pump. It increases the
pressure of the refrigerant vapor, and moves the
refrigerant through the system.
C. The condenser acts like a radiator in an automo-
bile, in that it removes heat from the engine and
transfers it to the outside air. In a refrigeration cycle,
the condenser cools (removes heat) the refrigerant
vapor which is heated as a result of the intense com-
pression (pumping) process of the compressor.
D. The expansion valve acts like a pressure reduc-
ing, flow control nozzle. The expansion valve will
automatically regulate the flow of refrigerant based
on the superheat value at the compressor inlet. This
is very important in order to ensure that only cool
vapor goes back into the compressor, and not liq-
uid, as liquid refrigerant intake will cause damage
to the compressor and/or oil dilution.
FORM 201.18-NM1.2
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