Troubleshooting Direct-Fired Air Handlers

In the event of the air handler not working properly, there are several areas in and around the heater to check for problems. Before resolving any issues, the following initial checks should be corrected:
  1. Compare voltage and phase of supply power on site with rating plate information.
  2. Review the wiring diagram connections between remote panel and control panel. Do the electrical connections match the supplied wiring diagram?
  3. Compare gas type and supply pressure on site with rating plate information. 
  4. Check for proper blower rotation on air handler and any exhaust blowers.
    • Blowers powered with a three phase motor can be reversed by swapping any two incoming power legs. For blowers powered by a single phase motor refer to the motor rating plate for reversing instructions. 

 MOTOR PROBLEM: MOTOR DOES NOT OPERATE

 POSSIBLE CAUSE

 SOLUTION

 Main disconnect switch is OFF

 Turn disconnect switch ON

 Blown fuse(s) in disconnect

 Replace fuse(s)

 Blown fuse(s)/breaker tripped in control transformer

 Replace fuse(s)/reset breaker (with disconnect off)

 Fan switch on, power on terminals 3 / 3A

 Check wiring between remote panel and air handler. Replace switch.

 Cool down timer TD4 (if equipped) does not reset. Power on 3A?

 Replace TD4 timer.

 Optional: Damper does not open

 Check that damper is not obstructed. Check that linkage is tight and secure. Verify 120V at terminal 3B. Replace damper actuator.

 Time delay relay defect. Power on terminal 3D after set time delay?

 Replace time delay relay TR1.

 Motor starter (contactor) does not operate. Power on terminal 3D and 2?

 Replace starter.

 Tripped motor overload. Power out to MUA motor when motor starter is energized?

 Reset. Check for proper FLA setting. Replace overload. If applicable, tighten screws on heater packs or overload.


 BLOWER PROBLEM: BLOWER DOES NOT OPERATE

 POSSIBLE CAUSE

 SOLUTION

 Belts broken or loose?

 Replace/tighten belts.

 Loose motor or blower sheaves (pulleys)?

 Reinstall and properly torque set-screws.

 Blower bearings, doe they turn freely?

 Replace bearing(s).


 BURNER PROBLEM: FLAME CONTROL DOES NOT TRY FOR IGNITION

 POSSIBLE CAUSE

 SOLUTION

 Auxiliary contact "M1" not closed. Power on terminal "4"?

 Properly mount contact or replace.

 Burner/winter switch closed? Power on terminal "7"?

 Replace switch.

 High temp limit switch tripped? Power on terminal "8"?

 Manually reset switch or replace.

 Low airflow pressure switch contacts not made. Power on terminal "8A"?

 Check blower operation. Reconnect tubes to pressure switch. Clean pressure test tubes. Check filters/duct work for restrictions.

 High airflow pressure switch contacts not made. Power on terminal "9"?

 Check blower FLA and compare to data plate. Cabinet pressure too high check system setup and for restrictions downstream of blower.

 Optional: Mild weather stat, dial set too low

 Set dial higher. Replace stat.

 Optional: High gas pressure switch

 Manual reset. Verify gas pressure.

 Optional: Low gas pressure switch

 Manual reset. Verify gas pressure.

 No power between terminals 3 and L2 (neutral) or 6 and L2 (neutral) for RM7890A (5 and L2 (neutral) or 7 and L2 (neutral) for RM7897C) of the burner control base

 Verify wiring.

 Flame control defect

 Replace.


 BURNER PROBLEM: BURNER LOCKOUT

 POSSIBLE CAUSE

 SOLUTION

 Failure to ignite pilot or main flame. Flame control failure.

 Reset the flame control module at the unit and proceed to the next step, observing the unit to indicate at which step lockout condition occurs.


BURNER PROBLEM: NO PILOT FLAME

 POSSIBLE CAUSE

 SOLUTION

 UV flame sensor indicating presence of flame before ignition. Flame indicator light present? Is there 5VDC on UV flame amplifier?

 Separate spark wire and UV scanner wires. Replace UV flame sensor, UV flame amplifier or burn control. 

 No spark

 Check wiring from burner control to ignition transformer. Check high tension wire to spark plug. Replace ignition transformer.

 No gas

 Open manual gas shut off valves. Check wiring from burner control to pilot gas valve. Verify inlet gas pressure. Adjust pilot gas pressure. Replace pilot gas valve. Check burner pilot opening for obstruction.


 BURNER PROBLEM: PILOT FLAME DOES NOT STAY LIT

 POSSIBLE CAUSE

 SOLUTION

 Improper pilot gas pressure

 Adjust pilot gas pressure.

 UV flame scanner does not detect flame. Is there 5VDC on UV flame amplifier?

 Replace UV scanner. Replace UV flame amplifier.

 UV flame scanner dirty

 Clean UV scanner


 BURNER PROBLEM: NO MAIN FLAME

 POSSIBLE CAUSE

 SOLUTION

 Manual shut off valve closed

 Open manual shut off valve

 Safety Shut Off Valve not operating. Is there positive gas pressure downstream of SSOV?

 Check wiring from burner control to SSOV. Verify inlet gas pressure. Replace SSOV.

 Minimum gas supply pressure

 Verify minimum gas supply pressure as per data plate is available

 Burner openings obstructed

 Remove obstruction. Clean burner orifices holes.

 Improper burner lower fire adjustment on modulating valve

 Adjust low fire as per the relevant Maxitrol temperature control instructions.


 
All installation and service of BANANZA® equipment must be performed by a contractor qualified in the installation and service of equipment sold and supplied by Bananza and conform to all requirements set forth in the BANANZA® manuals and all applicable governmental authorities pertaining to the installation, service, labeling and operation of the equipment. 
To help facilitate optimum performance and safety, Bananza recommends that a qualified contractor conduct, at a minimum, annual inspections of your BANANZA® equipment and perform service where necessary, using only replacement parts sold and supplied by Bananza.