72 YORK INTERNATIONAL
CAUTION: Before any changes are made, Subcooling
and Superheat must be correct. Incorrect re-
frigerant charge, restricted refrigerant flow,
incorrect chilled liquid flow, TXV misad-
justment/malfunction, or transducer prob-
lems will result in low motor current and/or
low suction pressure faults. Do not perform
any modifications unless no system prob-
lems exist. It is also advisable to consult
YORK Factory Service before changes are
made.
Fan cycling by discharge pressure can be accomplished
by performing the following:
1. Adjust the Low Ambient Temp. Cut-out to 0°F. This
can be accomplished by viewing Display Code 0, 7
and adjusting R1 on the Combo Board as low as it
will go (Typically 0 or .1).
2. Remove the OAT Sensor (Outside Air Temperature)
from the Combo Board by disconnecting it at plug
J17.
3. If a Low Ambient Kit is not present, a thermostat with
N.C. contacts set to open at 35°F must be connected
in series with the flow switch.
Compressor Capacity Control
The function of the compressor capacity control system
is to automatically adjust the compressor pumping ca-
pacity to balance with the cooling load at a pre-deter-
mined return water temperature and to permit the com-
pressor to start under partial load. The compressor ca-
pacity control system is actuated by means of high pres-
sure oil from the compressor oil pump. Oil pressure to
the power element loads the associated cylinders and
release of this pressure unloads them. Control of the oil
pressure to the unloader elements is the function of the
compressor capacity control solenoids located on the
front handhole cover. The compressor is loaded when
the solenoid is de-energized, and unloaded when the
solenoid is energized. Unloading is accomplished by lift-
ing and holding the suction valve off its seat. The gas,
drawn into the unloaded cylinders on the down stroke of
the piston, is pumped back into the suction chamber of
the compressor housing, without compression, when the
piston returns on its up-stroke. All cylinders equipped
with unloaders will remain unloaded on start-up until the
oil pressure has built up to normal. On each compres-
sor, certain cylinders do not unload. (See Fig. 53.)
DUAL CIRCUIT UNITS
FIG. 53 – COMPRESSOR UNLOADING SEQUENCE
CHILLER
NO. OF CYLINDERS
MODEL 60 HZ 50 HZ
YCAM12, N13
SYS 1 4 4
SYS 2 6 6
YCAK14, L15
SYS 1 6 6
SYS 2 6 6
YCAI16, J17
SYS 1 6 6
SYS 2 8 8
YCAG18, H19
SYS 1 8 8
SYS 2 8 8
LD01628
To Next Page
Loading...
