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NTI · Boiler

03 03 PCB internal error

High severity TRX

What the control is telling you

Internal fault on the main PCB.

Applies to: TRX150

Likely causes

  • Internal PCB fault

Test and repair steps

  1. Switch the boiler off and back on at the main electrical supply.
  2. If the problem returns, replace the main PCB.

Models that show this code

5 models in TRX

TRX085TRX110CTRX150TRX199TRX199C

Other codes on the same units

  • 02 09 Storage overheating
  • 2 P2 Anti-Legionella function not completely finished
  • 03 01 Display EEPROM error
  • 03 02 Communication error GP-GIU
  • 03 04 Too many resets in 15 minutes (more than 5)
  • 03 05 PCB internal error
  • 03 06 PCB internal error
  • 03 07 PCB internal error

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Source: NTI TRX150 manual, p. 91. 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.