Munchkin 80m roaring noise

Joe_91

...no it wasn't. Installed just like it came from the factory.
I bet it is gas valve related. When it gets a call for heat, senses that cold water, the brain tells it to "pour the coal" to the burner.......or something like that!
Maybe the combustion fan is ramped way up to be able to burn the large volume of gas and it overblows and the flame can't "catch up" and when I put my hand in front of the exhaust, the cfm flow drops and the flame manages to consume all the gas and stops the harmonics?
No, I am not a heating expert, but I did stay at a Super 8 (or whatever it is) motel last nite!!

Joe_91

Munchkin 80m roaring noise

I've got an 80m munchkin heating baseboard and a superstor tank in my house. Vision 1 equipped - Outdoor reset.
All winter my OWB was handling the load via a large brazed plate heat exchanger plumbed into the primary loop with the Munchkin. Worked just like I planned.
At the start of each call for heat, the Munchkin only fired for a little less than a minute til the temp in the primary loop recovered from the initial shock of the secondary circuits' cold water. I have the setpoint of the water set at 140*- that's where the munchkin fire goes out.
Now that it is warming up daily (60's and 70's), I let the fire go out in the OWB and isolated it from the plate heat exchanger.
Now, since I only get a call for heat a few times a day, the water in the secondary loop cools down to whatever temp it is in my crawlspace, when the Munchkin gets a call and fires, twice so far it make a sound I would characterize as what a vibratory sander on a 55 gallon drum would make. A loud, deep sound that I could even hear outside from my garage. It carries real well!
Anyway, the first time I noticed it, I went to see what the matter was. The sight glass showed that the fire was lit, but hadn't got the nice yellow glow going yet. I just turned off the power to the Munchkin, let it set, then turned it back on. Back to normal.
Today, I was out back in the garage and heard that distinct noise. Walked out the door and could tell it was the Munchking again. I just walked up to the exhaust and placed my hand over the outlet, and viola, the sound stopped and the heat/exhaust kept on flowing.
I suspect this is some harmonic vibration, caused from what?- I have no idea. It never did it when the primary loop temp stayed at a higher temperature when it was always cold out and the OWB was keeping the primary hotter via keeping the HX hot.
Any guesses or questions?

hr

Was the unit adjusted

and dialed in with a combustion analyzer?

The mod con "howl" is sometimes caused by mis-adjustment of the gas valve.

On the water side it's possible to get some noise from inadequate flow, or a scaled HX, but not usually a howl. More of a moan, like whale sounds

I'd suspect if you effect it by choking intake or exhaust it would be a gas valve adjustment.

I've had som LP units that had to be set slightly ouside of the "ideal" parameters to get the noise out. Do this with the analyzer and with factory guidence. Usually they (the factory) will note the adjustments and emission numbers when you "hyper" adjust them.

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hr

seek ye a

contractor with mod con tools and experience. Rare to find one perfectly adjusted out of the box. And how would you know?

Contact the local rep, or the manufacture to find a qualified serviceman.

They'd be able to look over the piping also.

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Joe_91

....Contractor?

The ones that sell Munchkin around here know zilch when it comes to hydronic piping. I've seen systems they've installed and I could give them lessons. This is forced air country and nothing else.

Our 3 story, huge brick junior high building (1923) was all steam heat. Had a bond issue to update the building, they tore out all the steam and put in forced air heat.
Was supposed to significantly lower their heating bills. A contractor friend of mine I asked about the building says the new bills are enormous and they asked him to come look at the system and see if he could "help" it out and he just threw up his hands and says they are on their own. He told me they had the designing engineer down to look and he basically was clueless, also.
I've got the Hydronics book by Seigenthaler and got that piping stuff figured out. Good diagrams in that book.
Now, I may be able to find someone out here with a combustion analyzer. I'll do some snooping and hopefully one will emerge with an analyzer and I'll get a clue.