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MUA-SVP01A-EN • Direct-Fired Indoor and Outdoor Units 27
Diagnostics
valve closest to the burner and measure the discharge air temperature. Is
it less than 130°F?
– Yes. There is a problem with the controller program or controller itself.
Contact the factory.
– No. The outside air temperature is too hot to determine the actual
cause of the problem. Reset the alarm and recheck when the outside air
temperature is much cooler.
– Yes. This signal is fed to the gas valve modulation signal conditioner.
Disconnect the wires from input signal terminals on the signal conditioner
and measure the voltage on the wires. Is it the same as the voltage
coming from the controller?
– No. There is an open in the wiring from the controller output. Correct
wiring and reconnect the wires to the terminals on the signal
conditioner. Be sure the ground wire from the controller output
terminal is connected to the signal conditioner's negative terminal.
– Yes. Continue.
4. Is there 24VAC on the signal conditioner power terminals?
– No. Determine cause and rectify.
– Yes. Continue.
5. Is there twice the DC voltage on the signal conditioner's output terminals as
there is on the signal conditioner's input terminals?
– No. Replace the signal conditioner.
– Yes. Continue.
6. Is the DC voltage on the modulating valve terminals the same as the DC
voltage on the signal conditioner's output terminals?
– No. There is a break in the wiring between the signal conditioner and the
modulating valve terminals. Determine cause and rectify.
– Yes. The electronics are working to this point. Continue.
7. Is there sufficient temperature rise for the amount of outside air that is being
delivered to the space?
– No. Follow the instructions in this manual for placing the unit in Manual
damper control mode. Adjust the Man. Vent setpoint to 20% outside air. Is
there sufficient temperature rise for the amount of outside air that is being
delivered to the space?
– No. Contact the factory.
– Yes. Continue.
– Yes. Continue.
8. Verify there is sufficient inlet gas pressure. Verify the modulating valve is
properly adjusted. Verify the burner orifices are clear of obstruction. Contact
the factory.