Inlet air filter
The filter behind the front panel that keeps dust out of the combustion air path on Rinnai's SENSEI RX. Washable, cheap, and the first thing to check on a blocked-air code.
What it does
A sealed-combustion heater pulls its air from somewhere — outside through the concentric vent, or from the room. Either way, dust and lint come with it, and anything that reaches the fan and burner degrades combustion. Rinnai’s SENSEI RX has a serviceable filter behind the front panel at the top right of the cabinet, with a pull tab.
Why it matters more than it sounds
A restricted air filter reduces combustion airflow, and that is one of the causes Rinnai lists for its blocked air supply or exhaust code — step 2 of that troubleshooting, right after checking the condensate drain. Cleaning it is free. The alternative diagnoses on that code are vent work and a fan motor.
Rinnai’s instruction is also explicit that the heater must not be operated with the air filter missing.
Cleaning it
Power the unit off at the controller, remove the two screws and release the two latches on the front panel, pull the filter out by its tab, scrub it with mild dish soap and a soft brush, rinse, dry it with a lint-free towel, and refit. Our guide covers the whole sequence, including how often it is worth doing.
Replace the filter if it is damaged or if it still looks dirty after a second wash.
What a replacement costs
$20-60 for the filter assembly, or nothing at all if it just needs washing.