Noisy/Smelly DHW combustion vent bothering neighboors

Mr. Tuttle

I recently had a new AO Smith Cyclone condensing hot water heater installed and I love it. It's providing plenty of hot water and I'm seeing a huge impact on the amount of gas we're using as opposed to the old heat exchanger off our steam boiler. Not running the boiler in the middle of Summer has been great.



So I'm ecstatic about it but my neighbors aren't as much. They're complaining about the noise as well as a gas smell coming from the vent. Usually there's a low rumbling sound when it's firing, but every once in a while there's also a banging noise. Is something wrong there or is that just how it is? Are there any kind of sound attenuators that are rated for condensing venting?



For the gas smell issue, I do detect a slight natural gas smell, especially at the start of the cycle, which I believe is some type of purge. Should I be worried that something is wrong with the firing? Should I have the utility come and check the gas levels at the vent? Most importantly, is there any way to reduce the smell?



Any answers or guidance is greatly appreciated! I'm getting in touch with a sales rep for the heater and will post any info I get from him.

Thank you

Mark Eatherton

Issues...

All gas fired appliance emit a slight gas odor when first started.



I am not aware of a noise attenuating muffler for any of the newer devices out there.



Have the installers or the gas company perform a combustion gas analysis.



Let us know what you find.,



ME

Jean-David Beyer

I am not a professsional, so keep that in mind.

"So I'm ecstatic about it but my neighbors aren't as much. They're

complaining about the noise as well as a gas smell coming from the vent.

Usually there's a low rumbling sound when it's firing, but every once

in a while there's also a banging noise. Is something wrong there or is

that just how it is?"



I have a gas burning mod-con. The loudest noise it makes is the circulators (Taco 007s). I can barely hear the blower in the boiler itself. It is easier to put my finger tips on the case and feel it.



So your "rumbling sound" when it is firing is either a different design where that is normal, or something out of adjustment. The banging noise worries me even more. Is it gas and air mixture exploding somewhere? I.e,. something like gas and air mixture going out the exhaust and igniting along the way?



It sounds as though you really need to get a pro in there with a digital combustion analyzer to see if everything is all right, and to fix it if it is not.

Greg Maxwell

Smelly vent

How far away is your neighbors house? Check the manufacturers instructions regarding vent distances from adjacent buildings, in a regular residential setting, they shoudnt be able to smell it at all, but if its too close, that may be why. I dont know of any reason why you should be getting any noise from that unit. It should be virtually silent, so you may have some other stuff going on. Contact the installing contractor for a review of the problem.

Mr. Tuttle

Further Investigation

Thanks for the advice guys, I think the consensus is right. The gas company came out and tested the exhaust vent during firing and found that there is no natural gas coming out, so that's good news.

I've also been in touch with a rep for AO Smith and they're going to send out someone to do a combustion analysis, something that looks like it wasn't done during the initial install. I'll post the results of that.

AO Smith also apparently makes a muffler for the exhaust side, which I'm going to try as well.

Our houses are pretty close together, by I think it's more an issue of my neighbors noticing as they walk between houses than when they're sitting in their living rooms with the window open.

Thanks again!