36
YORK INTERNATIONAL
SINGLE CIRCUIT UNITS
For extreme operating conditions, condenser fan opera-
tion may need to be modified to cycle the fans by dis-
charge pressure only. This should only be changed if
one of the following conditions result in low motor cur-
rent or low suction pressure faults.
1. Discharge pressures run below 140 PSI.
2. Glycol is being utilized and leaving chilled liquid tem-
peratures below 42°F are required.
3. Water is being utilized and leaving chilled liquid tem-
peratures 38°-40° are required.
The above conditions normally do not cause faulting,
however due to certain environmental conditions, wa-
ter/glycol flow rates, and glycol concentrations, this al-
teration may be required.
CAUTlON: Before any changes are made, subcooling
and superheat must be correct. Incorrect
refrigerant charge, restricted refrigerant flow,
incorrect chilled liquid flow, TXV misadjust-
ment/malfunction, or transducer problems
will result in low motor current and/or low
suction pressure faults. Do not perform any
modifications unless no system problems
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 predeter-
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 the compressor,
certain cylinders do not unload. (See Fig. 28.)
FIG. 28 – YCAQ10, R11 COMPRESSOR
UNLOADING SEQUENCE
CHILLER
NO. OF CYLINDERS
MODEL
60 HZ.
50 HZ.
YCAQ10, R11
8
18
LD01627
CONDENSER FAN LOCATIONS
AMBIENT TEMP.
FANS
Above 65°F
Fans C & D ON: 4 sec. after compressor start.
(18.3°C)
Fans A & B ON: 30 sec. after compressor start.
Fans C & D ON: 4 sec. after compressor start.
45°F (7.2°C) –
Fans A & B ON: Condenser Press > 300 PSI
65°F (18.3°C)
(2067 kPa)
OFF: Condenser Press < 230 PSI
(1585 kPa)
Fans C & D ON: Condenser Press > 260 PSI
(1791 kPa)
OFF: Condenser Press < 190 PSI
35°F (1.7°C) –
(1309 kPa)
45°C (7.2°C)
Fans A & B ON: Condenser Press > 300 PSI
(2067 kPa)
OFF: Condenser Press < 230 PSI
(1585 kPa)
<35°F (1.7°C)
Compressor OFF
STANDARD FAN CONTROL
LD01642
