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5567611-BIM-B-1218
minutes, and the SAT is greater than the upper SAT setpoint +
5°F, the compressor output energizes.
With a stage 2 cooling demand (Y2 input), the economizer
modulates to get the SAT to the lower SAT setpoint +/-5°F.
If the stage 2 cooling demand (Y2 input) remains on, the
economizer remains at 100% for 5 minutes, and the SAT is
greater than the lower SAT setpoint + 5°F, the compressor
output energizes.
If the economizer remains at the minimum position for 5
consecutive minutes, the compressor output turns off.
Cooling stages set to two or more for multiple compressor
units
With a stage 1 cooling demand (Y1 input) the economizer
modulates to get the SAT to the upper SAT setpoint
+/- 0.5°F.
With a stage 2 cooling demand (Y2 input), the economizer
modulates to get the SAT to the lower SAT setpoint
+/-.0.5°F.
If the stage 2 cooling demand (Y2 input) remains on, the
economizer remains at 100% for 5 minutes and the SAT is
greater than the lower SAT setpoint + 5°F, the compressor
output energizes.
If the economizer position remains at 100% for another 5
minutes, the next available compressor turns on. This process
repeats every 5 minutes until all the compressors energize.
If the economizer position drops below 100% and does not
reach the minimum position then returns to 100% and remains
at 100% for 5 minutes, the next available compressor
energizes. If the economizer position remains at 100%, the
process repeats every 5 minutes until all the compressors
energize.
Any time the economizer remains at the minimum position for 5
consecutive minutes, the last energized compressor turns off. If
it remains at the minimum position, the compressors de-
energize every 5 minutes until all the compressor are off.
Y3 and Y4 inputs have no additional impact on economizer
operation.
Sensor
CV option A occupied
When free cooling is available and the operating space
temperature is greater than the operating cooling setpoint, the
dampers modulate to control the upper SAT setpoint +/- 0.5°F.
If the economizer output is at 100% for 5 consecutive minutes
and the operating space temperature is 0.6°F or greater than
the operating cooling setpoint, the staged percent command
starts to increase and energizes compressors.
As soon as the staged percent command begins to increase,
the economizer remains at 100%. If the operating space
temperature drops to less than 0.6°F above the operating
42
cooling setpoint, the staged percent command holds the current
value.
If the operating space temperature drops 0.6°F or more below
the operating cooling setpoint, the staged percent command
begins to decrease.
If the staged percent command remains at 0 for 5 consecutive
minutes the economizer modulates to control to the upper SAT
setpoint +/-0.5°F.
CV option B occupied
When free cooling available and the operating space
temperature is greater than the operating cooling setpoint, the
dampers modulate to control the upper SAT setpoint +/-0.5°F.
If the economizer position remains at 100% for 5 consecutive
minutes, then the dampers modulate to control to the lower SAT
setpoint +/-0.5°F.
If the economizer position remains at 100% for 5 consecutive
minutes and the SAT is greater than the lower SAT setpoint
+5°F, the first compressor output energizes. If the economizer
position remains at 100% for another 5 minutes and the SAT is
greater than the lower SAT setpoint +5°F, the second
compressor output energizes. This process repeats every 5
minutes until all the compressors energize.
If the economizer position drops below 100% and does not
reach minimum position then returns to 100%, remains at 100%
for 5 minutes, and the SAT is greater than the lower SAT
setpoint +5°F, the next available compressor energizes. If the
economizer position remains at 100%, the process repeats
every 5 minutes until all the compressors energize.
Any time the economizer remains at the minimum position for 5
consecutive minutes or the SAT is lower than the lower SAT
setpoint -5°F, the last energized compressor turns off. If it
remains at the minimum position or the SAT remains lower than
the lower SAT setpoint -5°F, the compressors de-energize
every 5 minutes until all the compressors are off.
If all compressor outputs de-engerize, the economizer
modulates to control to the upper SAT setpoint +/-0.5°F.
When the cooling demand ends the compressors de-energize
immediately and the dampers return to the operating minimum
position.
CV option A and option B unoccupied
If the operating space temperature is greater than the
unoccupied cooling setpoint, the economizer modulates to
control to the lower SAT setpoint +/-5°F.
If the operating space temperature is greater than the
unoccupied cooling setpoint for 10 or more minutes, then all
compressor outputs energize with a 15 minute delay.
If the operating space temperature is less than the unoccupied
cooling setpoint -3°F, then all compressor outputs de-energize
and the economizer closes.
Johnson Controls Ducted Systems
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