NTI · Boiler

1 P3 Inadequate circulation or missing water (warning)

Normal status TRX

What the display is showing

Return minus supply temperature above 18 °F. Warning only.

Applies to: TRX150

Good to know

Low water pressure
Air in the system

Models that show this code

5 models in TRX

TRX085TRX110CTRX150TRX199TRX199C

Other codes on the same units

1 14 External (outdoor) sensor open or short circuit
1 16 Floor thermostat contact open
1 P1 Insufficient circulation or missing water (warning)
1 P2 Insufficient circulation or missing water (warning)
02 01 Damaged or shorted DHW temperature probe
02 03 Storage temperature probe open or short circuit
02 05 DHW inlet probe open circuit
02 09 Storage overheating

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Source: NTI TRX150 manual, p. 91. Summarized in our own words; check the original manual for your model.

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.