Rinnai Humming

[John Schneider]

I have a 12 year old Rinnai R94-LSi tankless water heater that has recently started humming. This only happens when first turning on the hot water full blast in a shower and stops after about 30-45 seconds. I wouldn't think its any kind of build-up in the pipes in the unit, as I do the vinegar flush once a year in the first week of December. I also have a whole-house water filter on the water line coming into the house.

Any ideas on what could be causing this?

 

[Plumber69]

I have a 12 year old Rinnai R94-LSi tankless water heater that has recently started humming. This only happens when first turning on the hot water full blast in a shower and stops after about 30-45 seconds. I wouldn't think its any kind of build-up in the pipes in the unit, as I do the vinegar flush once a year in the first week of December. I also have a whole-house water filter on the water line coming into the house.

Any ideas on what could be causing this?

Could be a loose part

 

[Sponsor]

 

[Fitter30]

Using lp to fire the heater? Lp can cause the burner to hum if air adjustment is off or burner is dirty. Air intake might have a air filter just inside the cabinet check your manual.

 

[John Schneider]

Could be a loose part

Thanks, I hadn't thought of that. Will check.

 

[John Schneider]

Thanks for the replies and the fix is really strange.
I occasionally have to take the fan out of the unit and clean it with compressed air when one of those helicopter leaves gets sucked into the air intake and jams the fan, throwing an error code 61. Last time I did this was last spring. Evidently, I didn't fully seat the rubber boot that connects the fan to the air intake. It had come completely off the fan. Once I put it back on and re-seated the spring clamp, the noise has gone.
I absolutely don't understand how this would have caused the loud humming, but its now gone away.

 

[Bannerman]

one of those helicopter leaves gets sucked into the air intake and jams the fan,

Is there no air filter to stop debris from entering the WH? Perhaps some window screen or filter foam could be added to the exterior air intake to prevent leaves, maple keys, insects etc from entering the WH air intake.

 

[Fitter30]

All that debris will stop up some of the burner ports. Might be time to pull the burner and blow it out.

 

[John Schneider]

Thanks for the replies. The screen on the intake is nowhere near as fine as a window screen. I have to assume that Rinnai designed it this way for a reason. The intake/exhaust port is pretty far away from trees or anything else that might get in. Just the occasional little helicopter leaf that is just barely small enough to get through the intake screen when it was very windy. In the 12 years I've had this unit, I believe there has only been 3 times one has been sucked in. Easy enough to pull the fan and blow it out using my air compressor.
As for the burner, that's one of the things I check every year when I do the flush. Haven't had any issues so far.