accidental dry fire on a Noritz tankless water heater

Jay Oxley

I am not sure how to find the fail safe but I will explore the possibility. Thanks so much!!

Jay Oxley

Noritz tankless water heater

I installed a new Noritz tankless water heater in my cabin. It worked great for the first 2 weekends. I then decided to drain my water lines for the winter and ran compressed air through them. I failed to turn the power off and dry fired the unit . It no longer works. There does't seem to be any reset.

Any ideas?

jp_2

fail safe sensor

there should be a fail safe on the heat exchanger. most likely not resetable but replaceable.

Jim Davis_3

Something doesn't sound right. The gas valve is activated by water flow and should not open if there is no water. Not sure how it could possibly dry fire???

Glenn Sossin_2

PROPELLER

Possibly - there is a water flow sensor - similar to a propeller. Air moving past it, especially at a high velocity, could cause it to spin making the unit think there was water flow.

Glenn

jp_2

that was my next

question, why did it dry fire? your answer sounds reasonable.

take the cover off and take a good look at the heat exchanger, you should find the sensor.

Rich Kontny_3

Dry Fire

A cabin application raises some red flags!

1. Type of water system and pressure differentials

2. Water quality (hardness? iron?)

3.Seasonal blow down and how you did it? It is possible the air flow lodged some debris in the fow switch and similated flow.

4.Power on was biggest problem as dry fire could not occur without it.

I just had a Takagi fail after 1.75 years on a test system I set up in my own home. I knew the conditions were quite tough for an on demand and I also have a supplemental "Heating Box" hooked up in series with it.

The heat source was a Takagi and they did replace it for a pro-rated fee and I do have to send it back to them for an autopsy.

Dry firing without water probaly did some permanent damage to your Noritz yet you may get lucky. Taking apart one of these is a little bit like working on a large watch with many small parts.

Let us know how this turns out. There is still a great deal to learn about field conditions and durability when it comes to on demand heaters.

Bob Sweet

Water quality

When I was a service provider for Rinnai, I had 2 occasions of HX failures both leaks were at the same location on the HX (upper right hand corner), imho I believe it was due to water quality. Both units were shipped back to Rinnai, never got an answer as to why.

These units were both installed on a water co-op feeding off the same source (very hard water). Water conditioning is a must for tankless water heaters.


Check the servo valve (flow sensor), if it was damaged it will not run.





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Jim Davis_3

Most tankless heaters I have checked use a diaphram much like a gas pressure regulator to open up the gas valve with water flow. Don't think a propellar would work. Even if the air leaked it couldn't have created enough flow to allow the heater to fire more than a few seconds.

Back in the 90's I sold Thermar, Vaillant & Aquastar Tankless heaters. I found that once we installed a Clearwave Water Conditioner on them we never had scale problems again.

Rich Kontny_3

Noritz Manual

From the Noritz manual:Page 18

Jay Oxley

Noritz tankless water heater

I want to thank everyone for their input. I will be going to my cabin this weekend and will take a look at the suggestions given on this forum. As far as water quality goes that is not a problem. Right now I am hauling city water to a buried 1000 gal. tank. I hope in the future to use my spring or to drill a well. I wished I was more qualified to know what I am doing. Anyone want to make a trip to the "wilds of Colorado?!"

Bob Sweet

Well

depending on were you are located I'm anywhere between 4 to 8/9 hrs from you, **** of a service call!!

Just can't see the unit allowing a dry fire, the compressed air up against the flow sense. Thats were I would start.

Good luck.

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