NTI Boiler: Replace the fan and mixer
Replace the fan and mixer on a NTI boiler: The fan and mixer on the TRX150 come off as one assembly, and that is how I usually do it. The thing that bites people is the fuel setup. The gas diaphragm and mixer are different for natural gas and propane, and a mismatch gives you bad combustion, rough starts or a lockout. Most fan jobs go wrong at reassembly, either a pinched O-ring or a missing gasket, which leaks and throws the combustion off.
Applies to: TRX150
Common causes of replace the fan and mixer
- Failed fan or noisy bearings after years of running
- Fan not reaching speed, giving blocked or low airflow errors
- Damaged mixer O-ring leaking air or gas
- Wrong gas diaphragm or mixer for the fuel type after a swap
How to fix replace the fan and mixer: step by step
- Turn off power and shut the gas supply before starting.
- Remove the silencer and gas line.
- Loosen the three screws holding the mixer to the fan. Check the O-ring is not damaged and replace it if it is.
- Loosen the three screws holding the fan to the heat exchanger.
- Reassemble the mixer and fan in reverse order with the O-ring between them.
- Reinstall the fan and combustion assembly and fit the gasket between the fan and air inlet channel.
- Confirm the gas diaphragm and mixer match the fuel (natural gas or propane).
- Leak-check the gas connection, then verify combustion with an analyzer. Gas work is for a licensed technician.
If the unit shows an error code, look it up: NTI Boiler codes
Source: NTI TRX150 manual, p. 99. 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.