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JOHNSON CONTROLS
FORM 100.50-NOM6 (1207)
5
Occupied Cooling – Stand Alone
The following System Parameters must be programmed
through the Simplicity Control for VAV Stand Alone
operation:
• “VAV COOLING SUPPLY AIR TEMP UP-
PER SETPOINT” – using Parameter 23 under
the PROGRAM key on the Simplicity control
board or under the COOLING SETUP tab in the
Simplicity PC software package.
• “VAV COOLING SUPPLY AIR TEMP LOWER
SETPOINT” – using Parameter 24 under the
PROGRAM key on the Simplicity control board
or under the COOLING SETUP tab in the Sim-
plicity PC software package.
• “VAV SUPPLY AIR TEMP RESET SETPOINT”
– using Parameter 25 under the PROGRAM
key on the Simplicity control board or under
the COOLING SETUP tab in the Simplicity PC
software package.
• “SPACE SENSOR FAULT OVERRIDE EN-
ABLED” must be turned on – using Parameter
8 under the PROGRAM key on the Simplicity
control board or under the SYSTEM OPTIONS
tab in the Simplicity PC software package.
The Simplicity Control will control the operation of the
compressors as follows:
• If the return air temperature is 2.0° F or more
above the “VAV SUPPLY AIR TEMP RESET
SETPOINT” the control will use the “VAV
COOLING SUPPLY AIR TEMP LOWER
SETPOINT”.
• If the return air temperature is not 2.0° F or
more above the “VAV SUPPLY AIR TEMP
RESET SETPOINT” the control will use the
“VAV COOLING SUPPLY AIR TEMP UPPER
SETPOINT”.
• If the control is using the “VAV COOLING
SUPPLY AIR TEMP LOWER SETPOINT” per
above the return air temperature must be equal
to or less than the “VAV SUPPLY AIR TEMP
RESET SETPOINT” before the control would
switch to the “VAV COOLING SUPPLY AIR
TEMP UPPER SETPOINT”.
• The control uses a 5-degree dead band around the
cooling “VAV COOLING SUPPLY AIR TEMP
UPPER SETPOINT” or “VAV COOLING SUP-
PLY AIR TEMP LOWERT SETPOINT”.
• When the supply air temperature is 5.0° F or more
above the cooling “VAV UPPER COOLING SAT
SETPOINT” or “VAV LOWER COOLING SAT
SETPOINT” the Simplicity Control will energize
the fi rst compressor.
• The control records the supply air temperature
right before the compressor is turned on and
compares it to the supply air temperature after 5
minutes of operation.
• A second compressor will be turned on if both of
the following criteria are met:
– The supply air temperature is still 5.0° F or
more, greater then the “VAV UPPER COOL-
ING SAT SETPOINT” or “VAV LOWER
COOLING SAT SETPOINT”.
– The Simplicity Control uses the temperature
difference calculated when the fi rst compres-
sor was turned on to verify the supply air tem-
perature will not drop 5.0° F or more below
the cooling “VAV UPPER COOLING SAT
SETPOINT” or “VAV LOWER COOLING
SAT SETPOINT”. If turning on a compressor
would result in the specifi ed drop in supply
air temperature, the second compressor will
not be turned on.
• The same logic will be used to stage on compres-
sor 3 and 4.
The Simplicity Control turns off compressor operation
as follows:
• The supply air temperature is 5.0° F or more
below the ““VAV COOLING SUPPLY TEMP
UPPER SAT SETPOINT” or “VAV COOLING
SUPPLY AIR TEMP LOWER SETPOINT”.
• It has been more than 5-minutes since the last
compressor was turned on.
• The compressors will be turned off in the reverse
order they were turned on.