YORK INTERNATIONAL
74
Sequence of Operation
FORM 100.50-NOM1 (604)
FIG. 42 –
EXHAUST PROPORTIONAL BAND
100%
Exhaust
Control Loop
Output
0%
minus Exhaust
Control Offset
plus Exhaust
Control Offset
Bldng. Press.
Setpoint
Building Pressure
LD06579
FIG. 43 –
EXHAUST FAN CONTROL
PRO
POR TION AL OPTION
LD06580A
The Primary Unit Controller will vary the position of
the modulating exhaust damper based on the “
Building
Pressure”
setting and the “
Exhasut Cntrl Offset”.
The
damper will modulate from 0 to 100% with a building
pressure range of the building pr/- the exhaust
control offset. Figure 42 illustrates this operation. The
constant volume exhaust fan will turn on and off based
on the position of the exhaust damper as follows:
• Fan ON when the position = EAD Position for the
Exhaust Fan to Turn ON. The damper position to
turn on is programmed through the parameter “EXH
DMPR Pos For ON”
• Fan OFF when the position = EAD Position for the
Exhaust Fan to Turn OFF. The damper position
to turn off is programmed through the parameter
“EXH
DMPR Pos For OFF”
• Exhaust fan OFF when Supply Fan is OFF
Figure 43 illustrates the On/Off operation of the exhaust
fan.
Proportional Exhaust Fan Control Based on
Building Pressure
This power exhaust option uses the building pressure
to vary the speed and air
ß
ow of a VFD exhaust fan.
The VFD exhaust fan will still be turn On/Off based on
the programmed position of the exhaust damper, even
though a damper is not installed, but once the VFD ex-
haust fan is on it will vary its speed and air
ß
ow based
on the “
Building Pressure”
.
This option requires the following:
• “
Economizer Enable”
ON
• Supply Fan – ON
• VFD exhaust fan
• Building Pressure Transducer
The VFD exhaust fan will turn on and off based on the
position of the exhaust damper as follows:
• Fan ON when the position = EAD Position for the
Exhaust Fan to Turn ON. The damper position to
turn on is programmed through the parameter “EXH
DMPR Pos For ON”
• Fan OFF when the position = EAD Position for the
Exhaust Fan to Turn OFF. The damper position
to turn off is programmed through the parameter
“EXH
DMPR Pos For OFF”
• Exhaust fan OFF when Supply Fan is OFF
After the VFD exhaust fan is turned on, the Primary
Unit Controller will vary the speed of the VFD Exhaust
fan based on the “
Building Pressure”
setting and the
“
Exhaust Cntrl Offset”.
Con
Þ
gurations employing Building Pressure requires
the installation of a pressure sensor in the condition
space and the connection of the sensor to the exhaust
fan transducer. The location of this sensor is critical for
proper operation of the exhaust fan. The sensor must
be located so that the building pressure in the area it is
monitoring is typical of the whole space.
ON
OFF
E xhaust Fan
Output
E AD P osition
for E F to Turn
OFF
E AD P osition
for E F to Turn
ON
E xhaust Fan
Turns Off
E xhaust Fan
Turns On
0%
100%