HVACopediaNTI · Boiler
01 06 Insufficient circulation or low water pressure
What the control is telling you
Return minus supply temperature above 18 °F, seen three times.
Applies to: TRX150
Likely causes
- Low water pressure
- Air in the CH circuit
- Faulty temperature probe or pump
Test and repair steps
- Check the water pressure on the gauge.
- Purge air from the central heating circuit.
- Check that the supply and return probes work and are positioned correctly.
- Check that the circulation pump works and is positioned correctly.
Models that show this code
5 models in TRX
Other codes on the same units
- 01 01 Overheat (CH circuit)
- 01 03 Insufficient circulation or low water pressure
- 01 04 Insufficient circulation or low water pressure
- 01 05 Insufficient circulation or low water pressure
- 01 07 Insufficient circulation or water
- 01 08 Low water pressure lockout (water pressure switch)
- 1 10 CH flow temperature probe open or short circuit
- 1 12 CH return temperature probe open or short circuit
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Source: NTI TRX150 manual, p. 90. Summarized in our own words; check the original manual for your model.
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