36 Direct-Fired Indoor and Outdoor Units • MUA-SVP01A-EN
Diagnostics

SOLUTION:If low airflow switch is opening. Do not adjust the switch

setpoints

1. Does low airflow switch open when the burner is off
–No. Disconnect both pressure sensing tubes from one of the airflow
switches and measure the differential pressure by connecting the high
sensing port of a manometer to one of the airflow sensing tubes and the
low sensing port to the other. Is the differential pressure approximately
the midpoint between the high and low airflow switch setpoints?
– No. Close the profile opening until the differential pressure is
approximately the midpoint between the high and low airflow switch
setpoints. Reconnect the sensing tubes, restart the burner, and verify
the airflow switch remains closed when the burner is at the maximum
rated input. Continue.
– Yes. Continue.
2. Are all of the filters dirty?
–Yes . Install clean filters and continue.
–No. Continue.
3. Does the external static pressure match that listed on the rating plate?
–No. Verify all associated ductwork is installed as designed, and there are
no obstructions. Continue.
–Yes . Continue.
4. Does the fan RPM match that listed on the Spec. Sheet?
–No. Correct to increased fan speed and continue.
–Yes . Continue.
5. Are the airflow switches' sensing tubes obstructed?
–Yes . Clear and continue.
–No. Continue.
6. Contact factory.
FAULT CODE: Clogged Filter Switch
PROBLEM: The filter air pressure switch has closed between the appropriate
terminals on the unit's terminal strip located in the unit's main control panel
indicating a clogged filter. See the Typical Wiring Schematic, Multiplexed Input,
and Clogged Filter sections of this manual for more information.

SOLUTION:If clogged filter switch is closing.

1. Are the filters dirty?
–Yes . Install clean filters and continue.
–No. Continue.
2. Are the airflow switch sensing tubes obstructed?