FORM 195.26-NM3
YORK INTERNATIONAL
69
Pressure Control Only,
Fan Control by Discharge Pressure
Fan control by pressure will operate 4 stages of fan
cycling according to the discharge pressure of the cor-
responding system. Ambient temperature will have no
effect.
1.
Until discharge pressure reaches 320 PSIG, no
system fans will operate.
2.
When discharge pressure reaches 320 PSIG fan
1 (7M) will be energized in the reverse direction.
This fan will remain energized until discharge
pressure drops below 120 PSIG.
3.
If discharge pressure of either system reaches
340 PSIG, the reversing fan on the respective
system will be turned off. At same time, fan 2
(6M) will energize. This fan will remain on until
discharge pressure of either system drops below
120 PSIG.
4.
If discharge pressure of either system reaches
360 PSIG and compressor run time has exceeded
30 seconds, fan 1 (5M) will energize turning the
fan in the forward direction. This fan will remain
on until discharge pressure of either system drops
to 140 PSIG.
Table 4 shows the operation of both modes of fan con-
trol previously discussed.
HOT GAS BYPASS (LOADMINDER) OPTION
General
The YORK Loadminder is a hot gas by-pass regulator
accessory which is factory mounted (field piping re-
quired) when ordered. Its purpose is to provide further
capacity reduction of the chiller below the last step of
compressor cylinder unloading by introducing an arti-
ficial load on the cooler. It provides steadier suction
pressure at minimum load conditions by keeping the
compressor on line rather than letting it cycle on and
off.
The Loadminder consists of a pilot operated regulating
valve with an integral solenoid. The pilot operated so-
lenoid is controlled by the microprocessor according
to suction pressure and system load.
The regulating valve is controlled by suction pressure
to modulate the flow of gas in a bypass connected
from the compressor discharge to the cooler inlet.
TABLE 4 – LOW AMBIENT FAN CYCLING
CONTROL BY
CONTROL BY
TEMPERATURE & PRESSURE
PRESSURE ONLY
FAN
CON-
BELOW 25°F
ABOVE 25°F
TACTOR
PRESSURE
TEMPERATURE
TEMPERATURE
CONTROL ONLY
CONTROL ONLY
HAS NO EFFECT
ON
OFF
ON
OFF
ON
OFF
Either System
Either System
1 REV
7M
Discharge
Discharge
Will Not Start
35°F or
320
120
Pressure Exceeds
Pressure Drops
Above 25°F
340 PSIG
PSIG
PSIG
320 PSIG
Below 120 PSIG
Either System
Either System
Turns OFF Only
2
6M
Discharge
Discharge
25°F
if Discharge
340
120
Pressure Exceeds
Pressure Drops
Pressure of Either
PSIG
PSIG
340 PSIG
Below 120 PSIG
System Drops
Below 120 PSIG
Either System
Either System
1 FWD
5M
Discharge
Discharge
45°F
40°F
360
140
Pressure Exceeds
Pressure Drops
PSIG
PSIG
360 PSIG
Below 140 PSIG
NOTE: A fan with a reversing contactor will have the reversing contactor mechanically locked out when Fan 1 is running forward.
The forward contactor will also be locked out when Fan 1 is running in reverse.
