YORK INTERNATIONAL
FORM 150.63-NM1
125
EVAPORATOR BLOWER CONTROL
The evaporator start contacts (CTB2 - terminals 23 -
24) are energized when any of the following conditions
are true:
1. Any compressor is running
2. Daily Schedule is not programmed OFF and
Unit Switch is ON.
The contacts will not close if the micropanel has been
powered up for less than 30 seconds or if the contacts
have been closed in the last 30 seconds to prevent mo-
tor overheating. These contacts can be used to start the
evaporator blower and for all practical purposes, will
be running in a “constant fan” mode. However, if the
blower is desired to cycle with the compressors, then
cycling of the evaporator blower can be achieved by
using the “Run Contacts” located at CTB2 - terminals
25 to 26 for system 1, or CTB2 - terminals 27 to 28 for
system two (if applicable).
CONDENSER FAN CONTROL
Condenser fan operation must be programmed with the
Options key under “Fan Control.” Condenser fan con-
trol 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
transducer is not installed, the condenser fans will op-
erate based on outdoor ambient temperature only. See
Table 21.
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 22. The fan control on-pressure
(ctrl_press) and fan differential off-pressure (diff_press)
are programmable under the PROGRAM key.
TABLE 21 – CONDENSER FAN CONTROL USING OUTDOOR AMBIENT TEMPERATURE
AND DISCHARGE PRESSURE
FAN STAGE
ON
OFF
FANS
OAT>25° F (-3.9°C)
OAT < 20° F (-6.7°C)
1 FWD.
Stage 1
OR
AND
DP > ctrl_press
DP < ctrl_press - diff_press
OAT>45° F (7.2°C)
OAT < 40° F (4.4°C)
Stage 2
OR
AND
2 FWD.
DP > ctrl 20 PSIG (1.38 Bars)
DP < ctrl_press - diff 20 PSIG (1.38 Bars)
3
FAN STAGE
ON
OFF
FANS
Stage 1
DP > ctrl_press
DP < ctrl_press - diff_press
1 FWD.
Stage 2
DP > ctrl_press + 20 PSIG (1.38 Bars)
DP < ctrl_press - diff 20 PSIG (1.38 Bars)
2 FWD.
TABLE 22 – CONDENSER FAN CONTROL USING DISCHARGE PRESSURE ONLY
Summary of Contents for MILLENNIUM YCUL0016SC
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