York ECO2 YPAL 050 - Manual (Page 70)

70 JOHNSON CONTROLS
FORM 100.50-NOM6 (1207)
Sequence of Operation
•
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 fi rst 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 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 fi rst 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 specifi ed 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 turn 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.
Cooling – Unoccupied with a Hard Wired or Com-
municated Space Sensor
The Simplicity Control cannot operate unoccupied
cooling with this method of control.
Heating – Occupied with a Hard Wired or Com-
municated Space Sensor
The following parameter must be programmed into the
Simplicity Control:
•
“VAV OCCUPIED HEATING ENABLED” – This
must be turned on using Parameter 26 under the
PROGRAM key on the Simplicity control board
or under the HEATING SETUP tab in the Sim-
plicity PC software package.
•
“MORNING WARM-UP/ VAV RETURN AIR
TEMP SETPOINT” – using Parameter 29 under
the PROGRAM key on the Simplicity control
board or under the HEATING SETUP tab in the
Simplicity PC software package.
•
“VAV OCCUPIED HEATING SETPOINT” – us-
ing Parameter 27 under the PROGRAM key on
the Simplicity control board or under the HEAT-
ING SETUP tab in the Simplicity PC software
package.
The unit will initiate Occupied Heating when the
following criteria is met:
•
The space temperature is 2.0° F less than the
“VAV OCCUPIED HEATING SETPOINT”.
•
The return air temperature is 0.1° F below the
“MORNING WARM UP / VAV RETURN AIR
TEMP SETPOINT”.
The unit will terminate Occupied Heating when the:
•
The return air temperature is equal to the
“MORNING WARM UP RAT SETPOINT”.
The “VAV OCCUPIED HEATING SETPOINT” should
always be set below the “MORNING WARM UP RAT
SETPOINT”.
Heating – Unoccupied with a Hard Wired or Com-
municated Space Sensor
The Simplicity Control cannot operate unoccupied
heating with this method of control.