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HTP · Boiler

F03 Return sensor failure

High severity Elite EL

What the control is telling you

Return temperature sensor has failed. Lockout, pump on. Control: FAULT light red steady and LOCKOUT shown on lower line; reset with RESET held over 1 second after repair.

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

Likely causes

  • Return sensor failed or wiring fault
  • Poor flow through the boiler

Test and repair steps

  1. Check circulator operation
  2. Confirm less than a 50 F rise from return to supply in the status menu
  3. Test the thermistor the same way as for F02

Models that show this code

12 models in Elite EL

EL-110 LPEL-110 NEL-150 LPEL-150 NEL-220 LPEL-220 NEL-299 LPEL-299 NEL-399 LPEL-399 NEL-80 LPEL-80 N

Other codes on the same units

  • E19 Line voltage frequency out of range
  • F00 Water high temperature (ECO)
  • F01 Flue temperature switch / low water
  • F02 Supply sensor failure
  • F04 Flue sensor failure
  • F05 Supply temperature high
  • F06 Return temperature high
  • F09 No flame on ignition

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Source: Elite EL-80 N Installation Manual (LP-293), p. 70. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.