JOHNSON CONTROLS
72
FORM 100.50-NOM6
ISSUE DATE: 8/07/2017
SECTION 5 – SEQUENCE OF OPERATION
•
“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.
The Simplicity Control initiates compressor operation
as follows:
•
The Simplicity Control will turn compressors ON
and off based of the difference between the supply
air temperature and the cooling setpoint.
• With no thermostat call or a Y1 first stage call the
Simplicity Control will control to the
“VAV COOL-
ING SUPPLY AIR TEMP UPPER SETPOINT”
.
The Y1 input is not required to initiate compressor
operation.
•
When there is a Y2, Y3, or Y4 call from the ther-
mostat the Simplicity Control will control to
the
“VAV COOLING SUPPLY TEMP LOWER
SETPOINT”
.
•
The control uses a 5-degree dead band around the
cooling
“VAV COOLING SUPPLY TEMP UP-
PER SAT SETPOINT”
or
“VAV COOLING SUP-
PLY AIR TEMP LOWER SETPOINT”.
•
When the supply air temperature is 5.0° F or more
above the cooling
“VAV COOLING SUPPLY
TEMP UPPER SAT SETPOINT”
or
“VAV COOL-
ING SUPPLY AIR TEMP LOWER SETPOINT”
the Simplicity Control will energize the first com
-
pressor.
•
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 above the
“VAV COOLING SUPPLY TEMP
UPPER SAT SETPOINT”
or
“VAV COOLING
SUPPLY AIR TEMP LOWER SETPOINT”
.
-
The Simplicity Control uses the temperature
difference calculated when the first compressor
was turned ON to verify the supply air tempera-
ture will not drop 5.0° F or more below the cool-
ing
“VAV COOLING SUPPLY TEMP UPPER
SAT SETPOINT”
or
“VAV COOLING SUPPLY
AIR TEMP LOWER SETPOINT”.
If turning a
compressor ON would result in the specified 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 be-
low 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.
Cooling – Unoccupied with Thermostat
The operation is the same as Occupied Cooling with a
Thermostat except:
•
A Y1 call will energize the supply fan.
•
The Simplicity Control will not bring on compres-
sors until the supply air temperature is 5.0° F or
more above the
“VAV COOLING SUPPLY TEMP
UPPER SAT SETPOINT”
or
“VAV COOLING
SUPPLY AIR TEMP LOWER SETPOINT”.
•
Both of the above criteria must be met before the
Simplicity Control will bring on compressors.
Occupied or Unoccupied Heating with a
Thermostat
“VAV OCCUPIED HEATING ENABLED” must
be programmed through the Simplicity Control. It is
turned ON using Parameter 26 under the PROGRAM
key on the Simplicity control board or under the
HEATING SETUP tab in the Simplicity PC software
package.
Any thermostat input will energize all the available
heat stages with a 30 second delay between stages.
Occupied Cooling with Hard Wired or
Communicated Space Sensor
The following System Parameters must be programmed
through the Simplicity Control for VAV operation with
a space sensor:
•
“VAV COOLING SUPPLY AIR TEMP UPPER
SETPOINT”
– using Parameter 23 under the
PROGRAM key on the Simplicity control board
