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UNIT TROUBLESHOOTING (cont)
PROBLEM POSSIBLE CAUSE CORRECTIVE ACTION
Constant outside air
(OAC) malfunctioning
OAC not enabled Enable OAC.
Fan status is OFF
Verify fan is operating and supply fan status is correct. Sup-
ply fan status must be ON to allow OAC control.
According to occupancy schedule, building
is unoccupied
Verify that current time and date are correct and reconfigure
occupancy schedule.
Incorrect unit type
Change unit type to VAV (1). OAC not available for CV
units.
Outside-air velocity pressure (OAVP) sensor
not functioning
Verify 24 vac power at sensor input and correct voltage at
sensor output. Verify that pneumatic tube from sensor to
probe is unblocked and correctly connected to the probe.
Verify that high-pressure side of probe faces the airflow.
Correct problems as necessary.
OAVP sensor not configured
Configure OAVP sensor for correct voltage and pressure
output ranges.
OAVP value does not match that of measure-
ment equipment
Verify above corrective action; adjust the probe multiplica-
tion factor (PMF) so that the OAVP reading matches that
of the measurement device. (OAVP value = sensor
value/PMF).
Indoor-air quality
(IAQ) features
malfunctioning
IAQ not enabled Enable IAQ.
According to occupancy schedule, building is
unoccupied
Verify that current time and date are correct and reconfigure
occupancy schedule.
IAQ priority level is incorrect
Verify that priority level is set at 1 or 2 and correct if
necessary. (Level 3 provides no IAQ control, only alarm
functions.)
Set point too high Adjust set point to correct (lower) level.
Air quality (AQ) sensors not operating
Ensure that power and control wiring are correct. Verify
24 vac power at sensor input and correct voltage at sensor
output.
AQ sensors not configured
Ensure that sensor voltage range and output values are
correctly configured.
IAQ type set incorrectly
Set IAQ type to 1 for a single sensor or two sensors used
for differential comparison. Set IAQ type to 2 for two sen-
sors used for separate readings.
IAQ functions suspended because priority level is
2 and the conditions below apply:
—
Space temperature is too high or too low Control will resume when space temperature recovers.
Space relative humidity is greater than cooling
coil high humidity limit (CCHHL)
Ensure that CCHHL is set correctly. Control will resume
when the relative humidity drops below CCHHL.
For VAV units only; supply-air temperature
(SAT) is greater than the sum of cooling coil
master reference (CCMR) plus 5 F,
or
SAT is
less than (CCMR−8 F) for 4 minutes or more
Control will resume when SAT control recovers. This is nor-
mal operation during conditions of high or low outside-air
temperature (OAT)
Mixed-air temperature (MAT) sensor is forced,
open, or shorted; OAT is less than 45 F;
MAT protection is enabled
Normal operation will resume when the MAT sensor is oper-
ating correctly or when OAT is greater than 45 F. If OAT is
greater than 45 F, remove force from, repair, or replace the
MAT sensor.
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