68
YORK INTERNATIONAL
COMPRESSOR CAPACITY CONTROL
FIG. 26
FAN LOCATIONS
LD02094
CHILLER
COMPRESSOR
# OF
# OF
MODEL
TYPE
CYLINDERS
UNLOADING STEPS
YEA
STANDARD OPTIONAL
Z88DR6
SYS 1 Z
6
5
N/A
SYS 2 Z
6
J44DR6
SYS 1 J
4
5
J44HT6
SYS 2 J
4
N/A
J54ES6
J55HT8
J65HT8
SYS 1 J
6
5
N/A
SYS 2 J
4
J66MT8
SYS 1 J
6
5
N/A
SYS 2 J
6
5
60 HZ
FAN CONTROL STRATEGY
ABOVE 25°F AMBIENT
The chiller is equipped with 4 condenser fans; 2 per sys-
tem. The standard fan control strategy is fan cycling by
outdoor ambient temperature, with the low ambient
cut-out (chiller shut down) set at 25°F.
Above 25°F ambient, a single fan on a respective sys-
tem will turn on 4 seconds after the compressor starts.
This fan will continue to run until the compressor shuts
down. This fan is designated as Fan 2 on SYS 1 and
Fan 4 on SYS 2.
If the ambient temperature is above 45°F, a second fan
on a respective system will start after the compressor
has run for 30 seconds. This fan will continue to run until
the compressor shuts down or until the ambient tem-
perature drops to 40°F. This fan is designated as Fan 1
on SYS 1 and Fan 3 on SYS 2.
Locations of the fans and a chart showing the operation
outlined above is shown in Fig. 26.
For operation below 25°F, a Low Ambient Kit MUST be
installed. See page 76.
The function of the compressor capacity control system
is to automatically adjust the compressor pumping
capacity to balance with the cooling load at a pre-
determined return water temperature and to permit the
compressor to start under partial load. The compressor
capacity control system is actuated by means of gas
pressure from the discharge side of the compressor.
Control of the gas pressure to the unloader elements is
the function of the compressor capacity control sole-
noids located on the front handhole cover. The compres-
sor is loaded when the solenoid is de-energized, and
unloaded when the solenoid is energized.
Capacity is reduced by unloading one or more banks of
cylinders. Some cylinder banks are not equipped with
unloaders. This prevents the possibility of overheating,
since a definite minimum volume of cool refrigerant gas
flows through the compressor at all times during opera-
tion regardless of load conditions.
Two types of compressors are utilized. To the right is a
list of models with the model number, style of compres-
sor, number of cylinders and available standard number
of steps of unloading.
CHILLER
COMPRESSOR
# OF
# OF
MODEL
TYPE
CYLINDERS
UNLOADING STEPS
YEA
STANDARD OPTIONAL
J44DR7
SYS 1 J
4
5
J55DR7
SYS 2 J
4
N/A
J55HT7
J65ES7
SYS 1 J
6
5
N/A
SYS 2 J
4
J66HT9
SYS 1 J
6
5
J76HT9
SYS 2 J
6
7
J77MT9
50 HZ
SYS. 1
SYS. 2
AMBIENT
AMBIENT
FANS
FANS
ON
OFF
2 (6M)
4 (9M)
25°F
24°F
1 (5M)
3 (8M)
45°F
40°F
