York YPAL 060, YPAL 061, YPAL 050 Occupied Cooling Stand Alone, VAV Supplyair Temp Reset Setpoint

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 SUPPLYAIR 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 SUPPLYAIR 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”.

FORM 100.50-NOM6 (1207)

•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 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, 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 first 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 specified drop in supply 5 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.

JOHNSON CONTROLS 71