Sequence of Operation
86
OAU-SVX006E-EN
Condensate Detection
Input will display a fault when
the switch located in the condensate pan for the indoor coil
has tripped.
Emergency Stop
will display a fault if the Emergency
Stop circuit is opened. Line 76 on the wiring diagram
shows the circuit to energize the Emergency Stop Relays.
The unit is shut down when this diagnostic occurs,
including the supply fan.
Compressor Low Ambient Lockout Active
will
display a fault if there is a demand for cooling according to
the setpoints, but the
Outdoor Air Temperature Active
is
below the
Compressor Low Ambient Lockout Setpoint
and
the unit does not have active head pressure control.
These diagnostic locks out compressor operation.
Diagnostic: Compressor [1, 2,...] Run Failure
is
displayed when there is a command for a compressor but
there is no active status for the compressor. Compressor
status is indicated using the NC contact on the compressor
auxiliary contactor.
Upon an initial call for a compressor, there is a five minute
and thirty second delay of no run status before an alarm is
indicated. If there is five minutes of continuous operation
with the run status, there is a thirty second delay before the
alarm is displayed.
The program will disable the output for that compressor if
there is run status alarm indicated. The diagnostic is
cleared when there is an alarm reset or the diagnostic has
been active for 3 hours.
Diagnostic: Compressor Fail Unit Lockout
is
displayed when there is a run failure diagnostic for one of
the compressors and the unit is supplying unsatisfactory
conditions for ten minutes. Unsatisfactory conditions are
identified by the
Discharge Air Temperature Local
is 2°F
above or below the
Discharge Air Temperature Setpoint
Active
during Heat Pump Heating or Cooling Mode, or
when the
Dehumidification Temperature Active
is 2°F
below the
Dehumidification Temperature Setpoint Active
during
Dehumidification Mode
.
The unit is shut down when this diagnostic occurs,
including the supply fan. The diagnostic can be cleared
with an alarm reset and will auto-reset once the
compressor run failure diagnostic is cleared.
Diagnostic: Condensate Overflow Unit Lockout
is
displayed when the
Condensate Detection Input
has
failed, and the unit is supplying unsatisfactory conditions
for five minutes. The unsatisfactory conditions use the
same criteria as the
Diagnostic: Compressor Fail Unit
Lockout
.
The unit is shut down when this diagnostic occurs,
including the supply fan. The diagnostic will auto-reset
five minutes after the condensate diagnostic has cleared.
Diagnostic: Heat Failure
is displayed after three failed
attempts to ignite the primary indirect fired gas heater
within a four-hour period. The unit is shut down when this
diagnostic occurs, including the supply fan
Diagnostic: [High, Low] Discharge Air Temp Lockout
is displayed when the
Discharge Air Temperature Local
is
[above 128°F, below 35°F] for a duration of 10 minutes. The
diagnostic is manual reset using
Alarm Reset
.
Diagnostic: Liquid Line Refrigerant Pressure Circuit
[1,2] Source Failure
is displayed when the respective
circuit is on (indicated by the compressor run status) and
the
Liquid Line Refrigerant Pressure Circuit [1,2]
falls
outside of the range of 150-650 PSI for a duration of two
minutes. When this occurs, the condenser fans will run at
100%
Diagnostic: Low Outdoor Coil Water Flow
is
displayed if the supply fan is running but the
Outdoor Coil
Water Flow Status
indicates that there is no flow for 20-
seconds. The compressors will be prevented from
operating when this diagnostic occurs and will auto-reset
once the flow returns.
The
Outdoor Coil Water Flow Status
is indicated using a
differential pressure switch across the inlet and outlet of
the water coils.
Diagnostic: Outdoor Coil Water Temperature Low
is
displayed if the supply fan is running but the
Outdoor Coil
Water Low Temperature Switch
indicates that the water
temperature is too low. The compressors will be
prevented from operating when this diagnostic occurs and
will auto-reset once the temperature switch closes.
The temperature switch is located on the water return and
the switch opens at 35°F for water, 20°F for glycol
Diagnostic: Low Refrigerant Suction Pressure
Circuit [1,2]
is displayed when the respective circuit is on
(indicated by the compressor run status) and the
Suction
Line Refrigerant Pressure Circuit [1,2]
Local falls below 85
PSI (55 PSI for heat pump heating) for two continuous
minutes. The diagnostic auto clears when the pressure
returns to normal.
Diagnostic: Outdoor Air Damper End Switch
is
displayed when
Outdoor Air Damper Open Close
Command
is On, but the
Outdoor Air Damper End Switch
does not prove for 3-minutes. The diagnostic is reset using
Alarm Reset
or when the end switch is proven.
Diagnostic: Return Duct/Space Pressure Setpoint
Range
is displayed when the
Return Duct/Space Pressure
Setpoint
is set within 20% of the maximum limit of the
Return Duct/Space Pressure Local
. If the setpoint is set too
close to the maximum range of the sensor, it will not be
able to recognize when it’s outside of the operating range.
Diagnostic: Duct Static Pressure Setpoint Range
is
displayed when the
Duct Static Pressure Setpoint BAS
is
set within 20% of the maximum limit of the
Duct Static
Pressure Local
. If the setpoint is set too close to the
maximum range of the sensor, it will not be able to
recognize when it’s outside of the operating range.
Diagnostic: Supply Fan Failure
is displayed when the
Supply Fan Start Stop Command
is On, but the
Supply Fan
Status
does not prove for two minutes. The diagnostic
requires a manual reset using
Alarm Reset
.