Table of Contents
Advertisement
Unit Controls
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
the heater is turned on. When the tempera-
°C)
ture rises above 45°F (7.2
°C)
under voltage condition will keep the heater off until full
voltage is restored to the system.
TABLE 36 – CONDENSER FAN CONTROL USING OUTDOOR AMBIENT TEMPERATURE AND DISCHARGE
PRESSURE
FAN STAGE
1 - 1 FAN FWD
2 - 2 FANS FWD
TABLE 37 – CONDENSER FAN CONTROL USING DISCHARGE PRESSURE ONLY
FAN STAGE
1 - 1 FAN FWD
2 - 2 FANS FWD
84
the heater is turned off. An
ON
OAT>25° F (-3.9°C)
OR
DP > ctrl_press
OAT>45° F (7.2°C)
OR
DP > ctrl_press + 20 PSIG (1.38 Bars) DP < ctrl_press - diff_press + 20 PSIG (1.38 Bars)
ON
DP > ctrl_press
DP > ctrl_press + 20 psig (1.38 Bars) DP < ctrl_press - diff_press + 20 psig (1.38 Bars)
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.
OAT < 20° F (-6.7°C)
DP < ctrl_press - diff_press
OAT < 40° F (4.4°C)
DP < ctrl_press - diff_press
OFF
AND
AND
OFF
YORK INTERNATIONAL
Advertisement
Table of Contents
