New Utica Tankless Boiler Booms and Rumbles

[Rick5150]

We just replaced an old Trianco boiler with a Utica Keystone UH3KW0.75 boiler. This is a tankless boiler that uses a powerventer directed directly through the back.

This is a brand new unit on January 28, 2020 and we are having a lot of trouble getting past the loudness of this boiler.

The main issue is that during startup, the powerventer will run as always for about 30 seconds, and then the boiler comes on with a boom. It will run with a rumbling noise for about 15 minutes before quieting down in bit. Once it shows off, the powerventer runs for about 2 minutes and then shuts off.

The other smaller issue is that the draft regulator really vibrates badly while the powerventer is on. If you touch it, it stops, but as soon as you let it go, it vibrates until the powerventer shuts off.

As this is a brand new boiler, I am hoping it is just a tuning issue. Any ideas are appreciated.

 

[Dana]

A 30 second flue purge seems a bit long- are you sure it isn't attempting to light up well before the "boom"?

The boom is an indication of an explosive mixture of unburnt fuel, something that a power-vented pre-purge is designed to prevent.

Did the installer use a combustion analyzer to set the air /fuel mixture properly?

 

[Sponsor]

 

[Rick5150]

Thank you for responding!

The technician never changed the power venter from the original settings when we had the Trianco. We have had that in place since 1990, bur midway through that we had to replace the power venter. It always had the 0:30/2:00 times. I cannot say for sure that it is not trying to relighting, but is doesn't sound like it.

They just tuned is yesterday, and were surprised to see that it is running at 86% efficiency. That is pretty lean. They used a few tools, but I have no idea what.

I am having them out Monday (the owner of the company) figure this out and to assess this boiler. Normally, I would be glad to mess around with things to check them out, but with a brand new boiler, I do not think I should have to.

In the past, I would look at the obvious stuff like nozzle size and electrode placement and once that is fine, it was always an issue of adjusting the air. But that is with one boiler, that I have had WAY too much experience with trying to keep it running. I do not want to start messing with things (personally) unless it is a last resort.

EDIT: I meant to mention that I always had no problems with the old boiler and we were using 80/0.75A nozzles. This new boiler is using 70/0.75B nozzles. Could the difference be due to the solid cone nozzle? Can a hollow cone nozzle help maybe?

 

[Fitter30]

Heres the book on the honeywell control. Purge has a 2 minute default timer page 7. Burner sounds lean.
https://www.google.com/url?sa=t&sou...FjAAegQIBhAD&usg=AOvVaw3I374WrzLdPgiBGmAIKRSO

 

[Rick5150]

The boiler is a lot quieter with the 70/0.75A nozzle, but it is still louder than I like it. I can live with it at this point, but the owner said it is about as loud as his boiler. I still think it can be improved.