
53
YORK INTERNATIONAL
FORM 100.50-NOM1 (604)
5
CONSTANT VOLUME SEQUENCE OF OPERATION
Under Constant Volume (CV) operation, the unit will
be controlled from one of the following sources in order
of priority:
• 7-Wire Thermostat.
• Space Sensor.
The Primary Unit Controller will monitor each source
and self-con
Þ
g ure to the source available with the high-
est priority.
Thermostat Control In CV Operation
Under thermostat control, the unit will monitor the G,
Y1, Y2, W1, and W2 thermostat inputs and control the
unit accordingly. Cooling Operation with Y1 and Y2
thermostat inputs are as follows:
Compressor Staging - ON:
• Y1 Only – Cooling Stage 1 – Both system 1
compressors and one of the System 2 or System 3
compressors on a six compressor unit.
• Y1 and Y2 – Cooling Stage 2 – All of the installed
compressor on System 1, 2 and 3 if applicable.
• If Y2 is present without Y1, the unit will stage on
Y1 per above and then stage on Y2.
Compressor Staging – OFF:
• Y2 Off – Shut off Cooling Stage 2 - It will shut
off one-half of the installed compressor. On a four
compressor system it will shut off the System 2
compressors. On a six compressor system it will
shut off three of the four System 2 and System 3
compressors.
TIMEOUTS AND DELAYS
Table 14 lists the timeouts and delays that are to apply
in all functions unless an exception for a speci
Þ
c func-
tion is speci
Þ
ed.
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TABLE 14 – TIMEOUTS AND DELAYS
*ASCD - Anti Short Cycle Delay
Number
Timeout or Delay
Description
1
*ASCD for cooling
This “minimum OFF time” delay will not allow any compressor to turn on,
unless it has been off for 5 minutes, except when ASCD override is ON.
2
*ASCD for “Cooling SAT Alarm”
This will not allow any compressor to turn ON after an excessive SAT trip has
occurred, until it has been off for 3 minutes.
3
*ASCD for “Heating SAT Alarm”
This will not allow any heat stage to turn ON after an excessive SAT trip has
occurred, until it has been off for 5 minutes.
4
*ASCD for heating
This “minimum OFF time” delay will not allow any heating stage to turn on,
unless it has been off for 2 minutes. Exception: Supply Air Tempering = 1 min.
5
Energy Saver Delay
This is a 1 minute minimum time between turning on
compressor stages or heating steps.
6
Minimum Run Time for Cooling
A minimum run time of 5 minutes will apply to all compressors.
7
Supply Fan *ASCD
This will not allow the Supply Fan to turn ON unless it has been OFF for 30
seconds.
8
Exhaust Fan Minimum Run Time
The exhaust fan will have a minimum ON time of 10 seconds.
9
Exhaust Fan Minimum Off Time
The exhaust fan will have a minimum OFF time of 1 minute.
10
Delay to allow SAT to stabilize
A 5 minute delay will be used any time a compressor, or a heating stage is
turned ON, or OFF, before using the SAT reading for any control decisions.