NTI Boiler: System water fill, purge and test
System water fill, purge and test on a NTI boiler: Fill and purge on the TRX150. Do it at install and after any service that opens the loop. Air in the system means noise, no flow, cold rads, pump cavitation. Condensate line goes on first so nothing gets wet when you fire it later. Purge zone by zone, then DHW.
Applies to: TRX150 and related TRX models
Common causes of system water fill, purge and test
- New install with a dry heat exchanger and piping
- System drained for service or a part swap
- Air trapped in a high point or a zone with no vent
- Pressure dropped after a leak or weeping fitting
- Combi DHW side not flushed after install
How to fix system water fill, purge and test: step by step
- Connect the condensate discharge pipe before filling and purging the heating circuit.
- Open the main water valve slowly until water flows. Do not open it fully.
- Purge each zone starting at the lowest point, closing it only when clear water with no air shows.
- Use the automatic air purge valve in the boiler and open the manual air vent if fitted.
- Keep filling until at least 12 psi shows on the pressure gauge.
- Watch that the boiler holds 12 to 15 psi during the purge, since pressure sags as air leaves.
- Purge DHW by opening faucets nearest the boiler first, then the farther ones, until water runs freely.
- Recheck the pressure gauge after a cycle or two and top up if it dropped.
If the unit shows an error code, look it up: NTI Boiler codes
Models
TRX085TRX110CTRX150TRX199TRX199C
Source: NTI TRX150 manual, p. 81, 77. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.