Sequence of Operation
FORM
The Simplicity Control will stage off the heat as follows:
•When the return air temperature is 2.4° F below the “CV OCCUPIED HEATING” or “CV UN- OCCUPIED HEATING SETPOINT” the third stage of heating will turn off.
•When the return air temperature is 1.9° F below the “CV OCCUPIED HEATING” or “CV UN- OCCUPIED HEATING SETPOINT” the second stage of heat will turn off.
•When the return air temperature is 0.1° F above the “CV OCCUPIED HEATING” or “CV UN- OCCUPIED HEATING SETPOINT” the first stage of heating will turn off.
The Simplicity Control has the following heating timing functions:
•A minimum off time of 2 minutes.
•A minimum on time of 3 minutes.
•There is a 30 second time delay between stag- es.
VARIABLE AIR VOLUME (VAV)
A Variable Air Volume (VAV) unit can be controlled by four methods:
•Stage thermostat
•Communicated Space Temperature
•Hardwired Space Temperature
•Stand Alone - Return Air Temperature
Cooling - Occupied with Thermostat
The following System Parameters must be programmed through the Simplicity Control for VAV operation:
•“VAV COOLING SUPPLY AIR TEMP UPPER SETPOINT” – using Parameter 23 under the PROGRAM key on the Simplicity control board or under the COOLING SETUP tab in the Sim- plicity 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.
The Simplicity Control initiates compressor operation as follows:
•The Simplicity Control will turn compressors on and off based of the difference between the sup- ply air temperature and the cooling set point.
•With no thermostat call or a Y1 first stage call the Simplicity Control will control to the
“VAV COOLING 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 thermostat the Simplicity Control will control to the “VAV COOLING SUPPLY TEMP LOWER SETPOINT”.
•The control uses a
•When the supply air temperature is 5.0° F or more above the cooling “VAV COOLING SUPPLY TEMP UPPER SAT SETPOINT” or
“VAV COOLING SUPPLY AIR TEMP LOWER SETPOINT” the Simplicity Control will energize the first 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 above the “VAV COOLING SUPPLY
TEMP UPPER SAT SETPOINT” or “VAV
COOLING SUPPLY AIR TEMP LOWER SETPOINT”.
68 | JOHNSON CONTROLS |
