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MUA-SVP01A-EN • Direct-Fired Indoor and Outdoor Units 29
Diagnostics
– Yes. This signal is fed to the signal conditioner. Disconnect the wires from
the signal conditioner's input signal terminals 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 wire from the controller's ground terminal is
connected to the signal conditioner's ground terminal.
– Yes. Continue.
5. Is there 24VAC on the signal conditioner power terminals?
– No. Determine cause and rectify.
– Yes. Continue.
6. 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.
7. 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.
8. 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.
9. 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.
FAULT CODE: Safety Circuit Open
PROBLEM:The controller has detected a failure in the safety circuit.
SOLUTION: If fan is not running (check prior alarm log)
1. Is there a prior alarm such as Unit On/Fan Off or Airflow Sw?
– Yes. See the Diagnostic section for the previous alarm.
– No. Continue.
2. Set Unit Mode to Manual. Did fan start?