York YPAL 060 Economizer / Compressor Operation, Economizer PI Loop Proportional and Integral

•When the space temperature is equal to or greater than 2.0° F above the “VAV SUPPLY AIR TEMP RESET SETPOINT” the Simplicity Control will use the “VAV COOLING SUPPLY AIR TEMP LOWER SETPOINT”.

Economizer / Compressor Operation

The Simplicity Control will use outdoor air without compressor operation when the following is true:

•Economizer is active.

•The outdoor air temperature is equal to or less then the economizer set point.

The Simplicity Control will use outdoor air with compressor operation when the following is true:

•Economizer is active.

•The outdoor air temperature is above the econo- mizer set point.

When outdoor air and compressor operation is available the compressors operation will be controlled as follows:

•If the supply air temperature is 5.1° F or more above the economizer set point and the Econo- mizer PI output is saturated (100%) the Simplic- ity Control will turn on a compressor and start a 3 minute timer.

•If after 3-minutes the temperature is still 5.1° F above the economizer set point and the Econo- mizer PI output is saturated (100%) the Simplic- ity Control will bring on a second compressor and start a three minute timer.

•This sequence would continue until all the com- pressors on.

•If after the 3-minute timing the supply air tem- perature is within +/- 5.0° F of the economizer set point no change will be made to the number of compressors operating.

•If after the 3-minute timing the supply air tem- perature is 5.1° F or more below the economizer set point and the Economizer PI output is low (dampers at the minimum position setting) the Simplicity Control will turn off a compressor.

FORM 100.50-NOM6 (1207)

•As long as the supply air temperature is 5.1° F below the economizer set point and the Econo- mizer PI output is low (damper at minimum position setting) the Simplicity Control will turn off compressors every 3-minutes until all the compressor have been turned off.

Economizer PI Loop (Proportional and Integral)

The Simplicity Control uses a proportional and integral logic (PI loop) to control the operation of the damper actuator. The Simplicity Control monitors the change in the supply air temperature to the economizer set point verses changes to the output to the damper actuator. When the supply air temperature is more then 2.0° F from the economizer set point the Simplicity Control will change the output to the economizer damper 1% every 2 seconds. If the supply air temperature is within +/- 2.0° F of the economizer set point the Simplicity Control will change the output to the economizer damper 0.5% every 2 seconds.

ECONOMIZER LOADING

Economizer Loading is a programmable option that can be used to place an artificial load on the unit to prevent cycling a compressor off when the supply air temperature approaches the “SUPPLY AIR TEMP LIMIT COOLING SETPOINT”.

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The following System Parameter must be programmed:

“ECONOMIZER LOADING ENABLE” – must be enabled under the COOLING SETUP tab in the Simplicity PC software package.

“SUPPLY AIR TEMP LIMIT COOLING SETPOINT” must be programmed using the COOLING SETUP tab in the Simplicity PC software package.

“SUPPLY AIR TEMP LIMIT FOR COOLING” must be enabled using the COOLING SETUP tab in the Simplicity PC software package.

JOHNSON CONTROLS 79