York J Series User Manual

JOHNSON CONTROLS
32
FORM 100.50-NOM7 (808)
Unit Sequence of Operation
CONTROLLING EXCESSIVE SUPPLY AIR
TEMPERATURE SAT
Excessive SAT is a condition under both cooling and
heating where the SAT is in excess of acceptable lim-
its. What this means is that operating past these limits
could possibly cause equipment damage, such as liquid
slugging compressors, dangerously high SAT, etc. This
section will describe the control override sequences nec-
essary to insure reliable operation.
Excessive SAT Control is selectable
ON or OFF for both heating and
cooling with the default setting ON
for each.
Excessive SAT Control for Cooling
There are two Excessive SAT control points for this
control sequence, Excessive Cooling SAT #1 setpoint
and Excessive Cooling SAT #2 setpoint. Excessive Cool-
ing SAT #1 will be used when only one compressor is
operating. This setting is intended to be used for units
equipped with Hot Gas Bypass which can allow system
#1 to operate at a much lower SAT when only one com-
pressor is operating. Excessive Cooling SAT #2 will be
used when more than one compressor is operating.
During Excessive SAT control for cooling, when the
SAT falls below the applicable Excessive Cooling SAT
setpoint for more than 1 minute, the control will destage
one compressor. The NextOFF buer will be used when
deciding which compressor to destage. An excessive
SAT fault will be written to the error history buer
along with a snapshot of the points data. Compressors
will continually be destaged until the SAT rises above
the applicable Excessive Cooling SAT setpoint.
When a compressor is destaged due to an excessive SAT
condition, the control will monitor the SAT and not al-
low another compressor to stage up until the SAT rises
above the applicable Excessive Cooling SAT setpoint
+ 5°F for 5 minutes.
Excessive SAT Control for Heating
This sequence will operate the same as cooling with
the only exception being that there will only be one Ex-
cessive Heating SAT setpoint. During heating operation,
when the SAT rises above the Excessive Heating SAT
setpoint for more than 1 minute, the control will destage
one step of heat. An excessive SAT fault will be written
to the error history buer along with a snapshot of the
points data. Steps of heat will continually be destaged
until the SAT drops below the Excessive Heating SAT
setpoint.
When a step of heat is destaged due to an excessive
SAT condition, the control will monitor the SAT and
not allow another step of heat to stage up until the SAT
drops below the Excessive Heating SAT setpoint - 10°F
for 5 minutes.
Setup
The control will read the Master/Subordinate Control
setting to determine if it is part of a Master /Subordinate
system and read the Master/Subordinate Conguration
setting to determine whether it is a Master or a Subordi-
nate. If it is a Master, it will monitor the Subordinate for
faults. If it is a Subordinate, it will monitor the Master
for control instruction. When the unit is powered up, the
unit control will check the conguration of the Master/
Subordinate Control setting and the Master/Subordi-
nate Conguration setting to determine if it is part of a
Master/ Subordinate.
System Control
The Master unit will operate normally per the input to
the control, i.e. thermostat, space sensor, network, etc.
The following information will be made available to
the Subordinate unit from the Master:
• VFD Position
• Unoccupied/Occupied Mode
• Current SAT Setpoint
• Current Demand Ventilation Multiplier
• Exhaust Damper/VFD Position
• Supply Fan ON/OFF
• Exhaust Fan ON/OFF
• Emergency Stop Status (Both Ways)
• Morning Warm-Up
The Subordinate unit will continuously follow the
Operation of the Master unit; however, all compressor
functions, heating functions (other than Morning Warm
Up) and ventilation functions (other than DVM) will
operate independently of the Master unit. For example,
three compressors may be required on the Master unit
to maintain a SAT of 55° when only two are required
on the Subordinate unit to maintain the same SAT. All
safeties will also operate independently from the Master
unit to the Subordinate unit, such as duct static over
pressurization, excessive SAT, etc.

York J Series Specifications

General

Brand	York
Model	J Series
Category	Air Conditioner
Language	English