Controlling Excessive Supply Air Temperature Sat; Power Exhaust Operation - York eco2 050 Installation Operation & Maintenance

Sequence of Operation
Sequence of Operation
The control will read the conÞ guration setting "Low
Ambient Confi g." to determine if low ambient hardware
is installed and on what systems. Low ambient hard-
ware can be installed on one, two, or three systems and
is indicated as follows by the "Low Ambient Confi g."
Setting:
0. No low ambient hardware installed.
1. Low ambient hardware is installed on system #1
only.
2. Low ambient hardware is installed in system #1 and
system #2.
3. Low ambient hardware is installed in system #1,
#2, and #3.
Only systems with low ambient hardware will be al-
lowed to operate below the Low Ambient Lockout
Tem per a ture.
Operation:
• If the Outside Air Temperature is above the Low
Am bi ent Lockout Temperature, the controller will
com mand all outputs for the VFD to 100%.
• If the OA Temperature falls below the Low Am bi ent
Lockout Temperature, the controller will check
for com pres sors operating. The control will then
stop any compressors operating from systems not
equipped with low ambient hardware. The control
will monitor and control the condensing pressure
on all sys tems equipped with the low ambient
hard ware. If the OA temperature falls to 0°F, all
me chan i cal re frig er a tion will be stopped by the
con trol ler and not allowed to restart until the OA
tem per a ture rises above +10°F.
• A +/- 1°F hysteresis will be used about the Low
Ambient Lockout Temperature.
Safeties
Communication Failure:
If the Primary Unit Controller detects a failure of the
N2 communication with the MOD UNT, a fault will be
generated and me chan i cal refrigeration below the Low
Ambient Lock out Temperature will not be allowed.
The MOD UNT will continue to operate the condenser
fans based on the measured discharge transducer in put
as last commanded by the DCU.
72
Unreliable Transducer:
If the discharge pressure becomes un re li able on any
sys tem, the controller will drive the VFD out put for that
system to 100% and prevent that sys tem from operat-
ing below the Cooling Lock out on OAT. A fault will be
generated.
CONTROLLING EXCESSIVE SUPPLY AIR
TEMPERATURE SAT
This feature is not used. "Excessive SAT- SAT Temper
Available" should always be conÞ gured to OFF.

POWER EXHAUST OPERATION

Power exhaust operation is used to control building
pressure. For building pressure control, the unit can
be equipped with the following exhaust air control
conÞ gurations. These parameters are selected under
"Power Exhaust Confi g".
• No power exhaust – "None"
• On/Off exhaust fan control based on the outside air
damper position – "2 Pos on OAD"
• On/OFF exhaust fan control based on the building
pressure– "2 Pos on EAD"
• On/Off exhaust fan control based on building
pressure and modulating exhaust damper position
– "Modulating"
• Proportional (VFD) exhaust damper control based
on building pressure – "Modulating"
For power Exhaust Operation, the parameter "Power
Exhaust Enable" must be programmed to ON and the
supply fan must be running.
On/Off Control Based on OAD Position
On/Off control based on OAD position controls the
powered exhaust fan ON or OFF based on the position
of the Outside Air Damper. This option requires:
• "Economizer Enable" ON
• Supply Fan – ON
• Constant volume exhaust fan
FORM 100.50-NOM1 (604)
YORK INTERNATIONAL