5167515-YIM-H-0518
38 Johnson Controls Ducted Systems
Once a compressor output is turned ON, the economizer
dampers continue to modulate to control the supply air
temperature to the Economizer Setpoint.
At no time will a compressor output be turned ON if the
economizer output is less than 100%, even if the differential
between zone (or return) temperature and the current cooling
setpoint is great enough to demand more than one stage of
cooling.
If the economizer output goes to minimum position and the SAT
is less than Economizer Setpoint -1°F, the control starts a 12-
minute timer to de-energize a compressor output.
If at any time the economizer output goes above the minimum
position the timer stops and resets when the economizer output
returns to minimum position.
If the demand for cooling from the space/return is satisfied, the
economizer output will modulate to minimum position and the
compressor outputs will be de-energized as long as their
minimum run timers have expired.
Power Exhaust
Setpoints
a. Economizer Enable ON
b. Power Exhaust Enable ON
c. Modulating Power Exhaust OFF
d. Exhaust VFD Installed OFF
e. Building Pressure Sensor Enabled OFF
f. Econo Damper Position For Exh Fan ON Percent
g. Econo Damper Position For Exh Fan OFF Percent
Inputs
No inputs are present for non-modulating power exhaust.
Outputs
a. 2-10 VDC from ECON on Economizer Expansion module
b. 24 VAC from EX-FAN to energize exhaust fan on
Economizer Expansion module
Operation
Operation details include:
a. Compares economizer output to the Economizer Damper
Position For Exhaust Fan On and OFF.
b. Energizes exhaust fan when economizer output is above
Economizer Damper Position For Exhaust Fan On.
c. De-energizes exhaust fan when economizer output is
below the Economizer Damper Position for Exhaust Fan
OFF
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