Economizer With Optional Vav Blower With Power Exhaust; Economizer With Optional Intelli-Comfort™ With Power Exhaust; Motorized Outdoor Air Dampers; Cooling Operation Errors - York SUNLINE MagnaDRY DR240 Installation Manual

284811-YIM-C-1008
Once the call for cooling has been satisfied, it will de-
energize any compressors and condenser fans, after
the minimum compressor run times have been satis-
fied. Otherwise, the unit operates each cooling system
until the minimum run times for the compressors have
been completed.
Upon de-energizing the final compressor, the blower
will continue to run with the economizer damper in its
minimum position if in the Occupied mode; otherwise,
the blower will stop following the elapse of the fan-off
delay for cooling, and the economizer outdoor damper
will close.
ECONOMIZER WITH OPTIONAL VAV BLOWER WITH
POWER EXHAUST
The power exhaust motor is energized via the control-
ler's EXH~ terminal and the ER relay, based on the
position of the economizer damper parameter settings
in the VAV control. Minimum run time is 10 seconds;
minimum off time is 60 seconds. The outlet pressure of
the power exhaust fan forces the barometric relief
dampers open; gravity closes the dampers when the
exhaust fan is off.
ECONOMIZER WITH OPTIONAL INTELLI-COMFORT™
WITH POWER EXHAUST
The power exhaust motor is energized via the exhaust
relay based on the position of the economizer actua-
tor's auxiliary switch adjustment screw. The adjustment
screw represents the outdoor damper position at which
to activate power exhaust, and can be set between 25
to 85 degrees open. The outlet pressure of the power
exhaust fan forces the barometric relief dampers open;
gravity closes the dampers when the exhaust fan is off.

MOTORIZED OUTDOOR AIR DAMPERS -

This system operation is the same as the units with no
outdoor air options with one exception. When the "R" to
"G" circuit is complete, the motorized damper drives
open to a position set by the thumbwheel on the
damper motor. When the "R" to "G" circuit is opened,
the damper spring returns fully closed.

COOLING OPERATION ERRORS

Each cooling system is monitored for operation outside
of the intended parameters. Errors are handled as
described below. All system errors override minimum
run times for compressors.
54

HIGH-PRESSURE LIMIT SWITCH

During cooling operation, if a high-pressure limit switch
opens, the UCB will de-energize the associated com-
pressor, initiate the ASCD (Anti-short cycle delay), and,
if the other compressor is idle, stop the condenser
fans. If the call for cooling is still present at the conclu-
sion of the ASCD, the UCB will re-energize the halted
compressor.
Should a high-pressure switch open three times within
two hours of operation, the UCB will lock-out the asso-
ciated compressor and flash a code (see Table 36). If
the other compressor is inactive, the condenser fans
will be de-energized.

LOW-PRESSURE LIMIT SWITCH

The low-pressure limit switch is not monitored during
the initial 30 seconds of a cooling system's operation.
For the following 30 seconds, the UCB will monitor the
low-pressure switch to ensure it closes. If the low-pres-
sure switch fails to close after the 30-second monitor-
ing phase, the UCB will de-energize the associated
compressor, initiate the ASCD, and, if the other com-
pressor is idle, stop the condenser fans.
Once the low-pressure switch has been proven (closed
during the 30-second monitor period described above),
the UCB will monitor the low-pressure limit switch for
any openings. If the low-pressure switch opens for
greater than 5 seconds, the UCB will de-energize the
associated compressor, initiate the ASCD, and, if the
other compressor is idle, stop the condenser fans.
If the call for cooling is still present at the conclusion of
the ASCD, the UCB will re-energize the halted com-
pressor.
Should a low-pressure switch open three times within
one hour of operation, the UCB will lock-out the associ-
ated compressor and flash a code (Table 36). If the
other compressor is inactive, the condenser fans will
be de-energized.

FREEZESTAT

During cooling operation, if a freezestat opens, the
UCB will de-energize the associated compressor, initi-
ate the ASCD, and, if the other compressor is idle, stop
the condenser fans. If the call for cooling is still present
at the conclusion of the ASCD, the UCB will re-ener-
gize the halted compressor.
Johnson Controls Unitary Products