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YORK INTERNATIONAL
74
Programming
The control panel may be programmed for AMBIENT
& DISCH PR FAN CONTROL (Ambient & discharge
pressure fan control) or by DISCHARGE PRESSURE
FAN CONTROL (fan control by discharge pressure
only). This is selected by placing SW. 8 on the Micro-
processor to the appropriate position. See page 29.
SW. 2 on the Microprocessor Board must also be pro-
grammed for LOW AMBIENT CONTROL to allow
operation at temperatures below 25°F. To accomplish
this, place SW. 2 in the CLOSED position. See page
28. After the switch is properly positioned, the OUT-
SIDE AIR TMP LOW CUT-OUT in the PROGRAM
mode can then be programmed between 0° - 25°F. See
page 28.
NOTE: For operation below 0°F, program the cut-out
for 0°F. This will cause the microprocessor to
ignore the low ambient cut-out regardless of
temperature.
Operation of the fans will be discussed in both Ambi-
ent and Pressure Control as well as Pressure Only
control in the following text.
Ambient and Pressure Fan Control 0°F - 25°F.
Fan operation below 25°F is controlled only by the dis-
charge pressure. Controlling action of the fans may be
dictated by either system. 4 steps of fan control oper-
ate as follows:
1. Until discharge pressure reaches 320 PSIG, the fans
will be completely off.
2. The second stage of fan control will energize fan 1
(7M) in the reverse direction when the discharge
pressure of either system exceeds 320 PSIG. Once
the reversing contactor is energized, it will stay on
until the discharge pressure of either system falls
below 120 PSIG, the ambient temperature exceeds
35°F, or discharge pressure of the system rises
above 340 PSIG.
NOTE: The corresponding compressor must be on for
a minimum of 4 sec. before the reversing fan
is permitted to start.
3. The third stage of fan control will energize fan 2
(6M) as well as turn off the reversing fan 1 when-
ever discharge pressure of either system exceeds
340 PSIG. This fan will stay on until discharge pres-
sure of either system drops below 120 PSIG.
NOTE: The corresponding compressor must be on for
4 sec. before this fan is permitted to start.
4. The fourth stage of fan control will energize fan 1
(5M) in the forward direction whenever discharge
pressure of either system exceeds 360 PSIG. This
fan will stay on until discharge pressure of either
system drops below 140 PSIG.
NOTE: The corresponding compressor must be on for
4 sec. before this fan is permitted to start. Fan
2 will also be operating.
Ambient and Pressure Fan Control 25° - 45°F
Fan control between 25° and 35°F is controlled by dis-
charge pressure. If the reversing fan is on, the revers-
ing fan will continue to operate until the temperature
reaches 35°F or discharge pressure reaches 340 PSIG.
At 35°F or 340 PSIG, fan 2 (6M) will energize. Between
25°F and 45°F if the reversing fan is not operating, af-
ter 4 seconds of compressor operation, fan 2 (6M) will
energize. This is identical to standard fan control by
temperature (Page 66). No pressure override exists. If
temperature drops below 25°F, this fan will remain on
until cycled off by discharge pressure of either system
dropping below 120 PSIG.
Ambient and Pressure Fan Control 45°F and Higher
Fan control above 45°F is strictly controlled by tem-
perature with no pressure override.
After 4 seconds of operation, fan 2 (6M) will energize
turning the fan in the forward direction.
After 30 seconds of operation, fan 1 (5M) will energize
turning an additional fan on in the forward direction.
This is identical to standard fan control by temperature
(Page 66). Fan 1 will de-energize if ambient tempera-
ture drops below 40°F.
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 sys-
tem fans will operate.
2. When discharge pressure of either system reaches
320 PSIG fan 1 (7M) will be energized in the re-
verse direction. This fan will remain energized until
discharge pressure of either system drops below
120 PSIG.
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