Takagi 510U Flame out (error 121)

[gmcmurry]

So I have a 2 week old Takagi Tankless that errors out about once every 24 hours. Gives me a 121 error which is a "flame out" error. I have been talking to tech support but so far nobody has an idea. If I reset the heater, it will work fine again. I cannot get through 24 hours without this happening.

Anybody have any ideas for me?

Greg

 

[Twowaxhack]

Just a guess......undersized/pressure on the gas line to it.

Has anyone connected a manometer and checked gas pressure at peak demand ? Just checked the gas pressure in general ?

Verify you have the correct heater fir the type gas you have. Propane or natural.

 

[gmcmurry]

This is the 2nd Takagi of the same model I have had in this installation. The other one sprung a bad leak at 5 years. I decided it would be easier for me to replace the whole thing than try to fix the old one.

I did put a monometer on the gas line. It measured 10 "h20 static and 8.7 when running. That should be enough.

I am trying to get Takagi to send me a new flame sensor to swap out but I don't have much hope that will work. I am afraid they will try to get me to change the whole computer board.

It does work most of the time. Just about once a day, I find it has errored out. Usually when I am not using it.

I do have recirc on this unit, so it does have to come on once in a while to keep the loop hot.

 

[Twowaxhack]

They should be able to walk you through the steps to test each part with a test meter instead of guessing.

If all the individual parts check out then it’s the brain board.

On Rinnai units if you replace the brain board you have to program the high and low fire with a manometer attached. It’s a process.

Good luck !