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,
i
ncluding the supply fan.
Compressor Low Ambient Lockout Active wi
ll
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
display
ed 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
ther
e 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
display
ed 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,
i
ncluding 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 Lo
ckout 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,
i
ncluding the supply fan. The diagnostic will auto-reset
five minutes after the condensate diagnostic has cleared.
Diagnostic: Heat Failure is displa
yed 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 display
ed 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 Refriger
ant 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 Ou
tdoor Coil Water Flow Status is indicated using a
differential pressure switch across the inlet and outlet of
the water coils.
Diagnostic: Outdoor Coil W
ater 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
C
ircuit [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 Ou
tdoor 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 d
isplayed 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 Press
ure 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.
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