LOU 24 volt supply low

What the control is telling you

Control's 24 V supply is damaged or overloaded; pump on. Clears itself if the overload goes away.

Applies to: EL-80, EL-110, EL-150, EL-220, EL-299, EL-399 (N/LP)

Likely causes

• Line voltage out of range
• Shorted external sensor wiring
• Short in the low voltage harness
• Optional UL353 low water cut-off loading the supply
• Gas valve drawing too much current at light-off
• Failed control board

Test and repair steps

1. Check line voltage is between 100 and 128 V
2. If available, connect a PC with the service software and check the 24 V reading: it should be above 128 and no more than 250
3. Unplug the 10-pin Molex from the customer connection board: if the message clears, look for shorts to ground in the external sensor wiring
4. If still present, disconnect the UL353 low water cut-off to see if it clears
5. Check the low voltage harness for shorts to ground
6. If it only appears when the burner tries to light, check the gas valve current draw
7. If it remains with the low voltage harness unplugged from the board, replace the control board

Models that show this code

12 models in Elite EL

Other codes on the same units

• FLU High flue pressure
• FOU Outdoor sensor fault
• GAS VALVE ON / RUN Ignition then run status
• LOCKOUT Lockout (display message)
• MAINTENANCE REQUIRED Service reminder
• PP Control programmed
• PRO Low water pressure
• SERVICE PUMP CH / DH / SH Pump service mode