Sequence of Operation
VAV Supply Fan Speed Control
The following values need to be programmed:
“DUCT PRESSURE SETPOINT” – Using parameter 30 under the PROGRAM key on the Simplicity control board or under the FAN tab in the Simplicity PC software package.
“DUCT PRESSURE SHUTDOWN SETPOINT”
–By using the FAN tab in the Simplicity PC software package.
The Simplicity Control uses a
On a call for supply fan operation the Simplicity Control sends a 24 VAC signal from the FAN terminal of the P13 connector to the supply fan relay.
The Duct Static Pressure Transducer has a range of 0.0 to 5.0” WC. The transducer sends a 0.0 to 5.0 volt DC signal to the Simplicity Control through the DP+ and DP- connections at the P21 connector. The Simplicity Control then sends a 2.0 to 10.0 volt DC signal to the supply fan VFD through the VFD+, VFD- terminals at connector P14 to vary the speed of the VFD.
If the duct static pressure is equal to or greater than the “DUCT PRESSURE SHUTDOWN SETPOINT” the Unit Controller will turn off all outputs and lockout until the control is reset.
ECONOMIZER
Economizer is used in the cooling mode only. As soon as the unit switches into Occupied or Unoccupied Cooling and the conditions are within the programmed guidelines for economizer operation the Simplicity Control will attempt to use outdoor air to lower the supply air temperature to the active economizer set point. The Simplicity Control can be configured to use the following economizer control methods:
•Dry Bulb
•Single Enthalpy
•Dual Enthalpy
FORM
The following parameter must be programmed to allow economizer operation:
“ECONOMIZER INSTALLED” – must be enabled using Parameter32underthePROGRAMkeyontheSimplicity control board or under the ECONOMIZER/EXHAUST tab in the Simplicity PC software package.
Dry Bulb
The following parameter must be programmed to allow economizer operation:
“ECONOMIZER OUTSIDE AIR TEMP ENABLE SETPOINT” – must be programmed using Parameter 39 under the PROGRAM key on the Simplicity control board or under the ECONOMIZER/EXHAUST tab in the Simplicity PC software package.
The economizer will become active and use outdoor air for cooling when:
•The outside air temperature is less then or equal to the “ECONOMIZER OUTSIDE AIR TEMP ENABLE SETPOINT”.
•The Simplicity Control has a demand for cooling operation.
•If the outdoor air temperature was above the
“ECONOMIZER OUTSIDE AIR TEMP ENABLE SETPOINT” when the cooling cycle was initi- ated, the Simplicity Control will activate econo- mizer operation when the outdoor air temperature is 1.0° F below the “ECONOMIZER OUTSIDE AIR TEMP ENABLE SETPOINT”.
The economizer will become inactive and eliminate the use of outdoor air for cooling when:
•The outside air temperature is 1.0° F greater than the “ECONOMIZER OUTSIDE AIR TEMP EN-
ABLE SETPOINT”.
•The Simplicity Control does not have an Occu- pied or Unoccupied cooling demand.
76 | JOHNSON CONTROLS |
