Tankless Water Heater Ignition Issue

I have a Rheem tankless water heater that sporadically displays Error Code 11: No Ignition. This happens maybe 1 in 50 times of use. Other times it works normally. Essentially the heater fires up, ignites, and shortly after the flame goes out. Checked the ignition system and seems to be in working order. Coincidentally I am having a similar issue with a gas-powered furnace. Turns on, but after a minute or so shuts off.

I'm wondering if these problems could be related and if it has something to do with my gas line. Both appliances seem to be in working order, but it seems like some kind of gas safety mechanism is kicking in and shutting down the units. If it wait an hour or so, everything is back to normal.

Any thoughts? Help is greatly appreciated. Thank you.

Check the gas pressure, that’s a common factor. Contact your local gas supplier, they have the necessary pressure gauge and expertise. If it’s a failing regulator or meter, it’s usually their responsibility to replace or repair.

It may also be a dirty pilot on both. Or more specific, a dirty flame rod. If you have medium mechanical skills you can probably clean both yourself. Look on You Tube, there’s multiple clips for both.

Thank you very much. I was thinking it might be related to the gas pressure. I've made an appointment with The Gas Company to take a look.

Are you on city water or a water well? Many times the well pump cycling on and off, causing the pressure to fluctuate between 40 and 60 over and over will reduce flow in the shower at low pressure and the flame will go out. I have heard it called a cold water sandwich. Lol!

Great news! Everything is fixed. Turns out it was a failing regulator, which the gas company came out and replaced.

Thanks for all your help!

Valveman said:

Are you on city water or a water well? Many times the well pump cycling on and off, causing the pressure to fluctuate between 40 and 60 over and over will reduce flow in the shower at low pressure and the flame will go out. I have heard it called a cold water sandwich. Lol!

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This is incorrect. 40 psi is plenty for a tankless to operate.