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NTI · Boiler

FILL - 108 Low water pressure lockout

High severity TRX

What the control is telling you

If water pressure drops below 7 PSI, the control shows this blocking error and stops burner operation.

Applies to: TRX150, TRX199, TRX199C

Likely causes

  • Water pressure in the system drops below 7 PSI

Test and repair steps

  1. Refill the system to bring water pressure back above 7 PSI.
  2. Check for leaks before and after refilling.

Models that show this code

5 models in TRX

TRX085TRX110CTRX150TRX199TRX199C

Other codes on the same units

  • 5 P3 Flame loss during run
  • 5 P6 3rd and 4th ignition failed
  • 06 02 Exhaust temperature above 204 °F (96 °C)
  • 06 03 APS open
  • 06 05 Exhaust NTC circuit open or short circuit
  • 6 12 Insufficient fan speed
  • EMERG Incorrect wiring to BUS connection (emergency mode)
  • NOAVL PCB error: boiler application not set

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Source: NTI TRX150 manual, p. 31. 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.