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YORK INTERNATIONAL
84
EVAPORATOR PUMP CONTROL
The evaporator pump dry contacts (CTB2 - terminals 23
- 24) are energized when any of the following conditions
are true:
1. Low Leaving Chilled Liquid Fault
2. Any compressor is running
3. Daily Schedule is not programmed OFF and
Unit Switch is ON.
The pump will not run if the micropanel has been pow-
ered up for less than 30 seconds or if the pump has run
in the last 30 seconds to prevent pump motor overheat-
ing.
EVAPORATOR HEATER CONTROL
The evaporator heater is controlled by ambient air tem-
perature. When the ambient temperature drops below
40°F (4.4
°C)
the heater is turned on. When the tempera-
ture rises above 45°F (7.2
°C)
the heater is turned off. An
under voltage condition will keep the heater off until full
voltage is restored to the system.
CONDENSER FAN CONTROL
Condenser fan operation must be programmed with the
Options key under “Fan Control.” Condenser fan control
can be selected for Ambient Temp. and Disch. Pres-
sure, or Discharge Pressure Only.
The condenser fan control by “Ambient Temperature and
Discharge Pressure” is a feature that is integral to the
standard software control. If the optional discharge trans-
ducer is not installed, the condenser fans will operate
based on outdoor ambient temperature only. See Table
36.
The condenser fan control by “Discharge Pressure” is a
feature that can be selected if the discharge pressure
transducer is installed and fan recycling is not a con-
cern. Fan control by discharge pressure will work ac-
cording to Table 37. The fan control on-pressure
(ctrl_press) and fan differencial off-pressure (diff_press)
are programmable under the PROGRAM key.
TABLE 36
– CONDENSER FAN CONTROL USING OUTDOOR AMBIENT TEMPERATURE AND DISCHARGE
PRESSURE
FAN STAGE
ON
OFF
OAT>25° F (-3.9°C)
OAT < 20° F (-6.7°C)
1 - 1 FAN FWD
OR
AND
DP > ctrl_press
DP < ctrl_press - diff_press
OAT>45° F (7.2°C)
OAT < 40° F (4.4°C)
2 - 2 FANS FWD
OR
AND
DP > ctrl 20 PSIG (1.38 Bars) DP < ctrl_press - diff 20 PSIG (1.38 Bars)
TABLE 37
– CONDENSER FAN CONTROL USING DISCHARGE PRESSURE ONLY
FAN STAGE
ON
OFF
1 - 1 FAN FWD
DP > ctrl_press
DP < ctrl_press - diff_press
2 - 2 FANS FWD
DP > ctrl_press + 20 psig (1.38 Bars) DP < ctrl_press - diff 20 psig (1.38 Bars)
Unit Controls
Содержание MILLENNIUM YCAL0043SC
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