IM 613 / Page 20 (Rev. 7/99)
Brownout
The “Brownout” fault indicates that the UVC is sensing low
voltage levels. It is a safety that is intended to protect the
compressor and electric heat contactors from low line voltage or
“brownout” conditions.
The controller is programmed with a brownout setpoint that
corresponds to 85% of the unit ventilator’s nameplate line
voltage value. If the UVC senses a voltage level less than its
setpoint for more than 10 seconds (2 seconds with electric heat),
it will trigger the brownout fault. The fault will reset when the sensed
voltage remains at or above a level corresponding to 90% of the
nameplate value for a period of 5 minutes. For information on
troubleshooting this alarm, refer to “Test Procedures” in the
“Service Information” section of this manual.
Effects (as applicable):
• Compressor is immediately de-energized.
• All electric heat stages are immediately de-energized.
Heating Valve Position Feedback Failure (4-Pipe Units Only)
The “Heating Valve Position Feedback Failure” fault is an
indication that the UVC is sensing a valve position feedback
voltage that is outside the acceptable range. Refer to “Test
Procedures” in the “Service Information” section of this manual
for information on troubleshooting actuator feedback faults.
Effect:
• Heating valve will hold its position.
Valve or Face and Bypass Damper Position Feedback Failure
The “Valve or F&BP Damper Position Feedback Failure” fault is
an indication that the UVC is sensing a valve or F&BP damper
position feedback voltage that is outside the acceptable range.
Refer to “Test Procedures” in the “Service Information” section of
this manual for information on troubleshooting actuator feedback
faults.
On 4-pipe valve controlled units, this fault applies to the chilled
water valve. On all other units with control valves or F&BP
dampers, there is only one possibility: heating valve, chilled
water valve, or F&BP damper actuator.
Effect:
• Valve or actuator will hold its position.
Outdoor Air Damper Position Feedback Failure
The “Outdoor Air Damper Position Feedback Failure” fault is an
indication that the UVC is sensing a damper position feedback
voltage that is outside the acceptable range. Refer to “Test
Procedures” in the “Service Information” section of this manual
for information on troubleshooting actuator feedback faults.
Effect:
• Outdoor air damper will hold its position.
Discharge Air Temperature Sensor Failure
The “Discharge Air Temperature Sensor Failure” fault will occur
when the voltage across the discharge air sensor is outside the
acceptable range. Refer to “Test Procedures” in the “Service
Information” section of this manual for information on trouble-
shooting sensor faults.
Effects (as applicable):
• Control Temperature is set equal to the room temperature.
• Discharge air low limit functions are disabled.
• Discharge air high limit function is disabled.
• All other control processes execute normally (discharge air
temperature is assumed to be acceptable).
Outdoor Air Temperature Sensor Failure
The “Outdoor Air Temperature Sensor Failure” fault will occur when
the voltage across the outdoor air sensor is outside the
acceptable range. Refer to “Test Procedures” in the “Service
Information” section of this manual for information on trouble-
shooting sensor faults.
Effects (as applicable):
• Economizer cooling is disabled (ventilation cooling lockout
function assumes OA temperature is high).
• Compressorized cooling is disabled on all except AR unit
(low ambient compressor lockout function assumes OA
temperature is low).
• On ASHP units, electric heat can be enabled by the
emergency heat, defrost, or discharge air low limit
functions only (OA temperature is assumed to be high).
• Heating EOC valve is controlled by room temperature only
(OA temperature is assumed to be high).
Water-In Temperature Sensor Failure
The “Water-In Temperature Sensor Failure” fault is applicable to
WSHP units and to units equipped with water coils (except for
4-pipe valve controlled units). It will occur when the voltage across
the entering water temperature sensor is outside the acceptable
range. Refer to “Test Procedures” in the “Service Information”
section of this manual for information on troubleshooting sensor
faults. Note: Except for 2-pipe units, this fault will not affect the
normal operation of units equipped with water coils.
Effects (as applicable to WSHP units):
• Economizer changeover function depends on OA
temperature only (entering water temperature is assumed
to be high).
• Compressorized heating is available (entering water
temperature is assumed to be high).
• Electric heat can be enabled by the emergency heat or
discharge air low limit functions only (entering water
temperature is assumed to be high).
Effects (as applicable to 2-pipe units):
• Valve or face and bypass damper cooling operation is
disabled (entering water temperature is assumed to be
high).
• EOC valve will act as a heating EOC valve (entering water
temperature is assumed to be high).
Water-Out Temperature Sensor Failure
The “Water-Out Temperature Sensor Failure” fault will occur when
the voltage across the leaving water temperature sensor is
outside the acceptable range. Refer to “Test Procedures” in the
“Service Information” section of this manual for information on
troubleshooting sensor faults.
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