Takagi TK2 running at full blast constantly

[tomallinder]

I have the book but says nothing about the water heater running at full blast constantly. Filter is clean. It is providing hot water but will not shut down... Please help!

Thanks!

Tom

[hj]

Shut off the water supply and see if it shuts down. If it does you have a hot water leak. If it does not, the heater should be banging and pounding like crazy as it becomes a steam boiler.

[tomallinder]

Thanks hj, I will file that away for future reference. The last time the TK2 ran full blast, it was because the filter was clogged with sand... This time, I cleaned and changed all the filters but still ran full blast...

It gradually wound down over 30 minutes and is working (apparently) normally now. Not sure what caused the episode. We did have a power hit just before this happened though... Not sure what that would have to do with it.

Thanks again!

Tom

[MACPLUMB 777]

I Could Say Something Funny Like Get Some Rope And Tie It Down Before It Gets Away From You,

But Really You Need A Licensed Electrician To Wire A Surge Suppressor On That Circuit That The Heater Plugs Into To Keep From Frying The Board ! ! !

[master plumber mark]

If nothing was running in the home, and the unit was
trying to blast off like a .... F14-Tomcat....for 20 minutes

how come the t+p valve did not go off and relieve the pressure???

I would be worried that your unit has sustained
some pressure related damages to the heat exchanger
from this episode..


and I seriousley would change out your t+p valve.

that had to be one hot puppy........

[hj]

One reason is that the majority of tankless heaters, any brand, do not have T&P valves. They have "P" valves because the units are so well controlled that they cannot "run full blast" without a water flow, at least that is what the small print says. I, for one, do not believe it so I always add a T&P valve to the installation. But if it runs for ANY AMOUNT OF TIME without flow the heater WILL start hammering because it it generating steam. THEREFORE, if it is running and not banging there is a flow somewhere.