Rattling metal noise in gas furnace


Old 01-15-16, 10:27 AM
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Rattling metal noise in gas furnace


There is a rattling noise from inside the wall when one of our gas furnaces is running. Please note: I don't intend to do any DIY here. I am just wondering if folks think this is more of a HVAC issue and I should call a heating and air place, or my gas company.

I really just started noticing it getting worse in the past few weeks. But the issue is not new. We bought this home late last winter, and I recall hearing it a time or two then, as well. But I live in Carolinas, and we didn't have to run the heat often last year. And just really started using it for this season in past few days.

Here is the odd thing. The house has multiple gas furnaces. One in the crawlspace under the house (for 1st floor), one in the attic (above my master BR) for the second floor + third floor attic playroom, and one for an addition (way across the house).

So the thing is, I hear the rattling in the wall right behind my headboard in master BR....but only when the downstairs/crawlspace unit is running. Not the one up in the attic. If it was the reverse, would make more sense to me. Again, sounds like a rattling, starts slow, gets stronger and only happens when the furnace under the house is running. I am worried its a pipe or something loose. I have not gone under the house to see if its louder there. I can access the attic where the second story furnace is, and I can hear it loud/clear in there. But again....that's not the unit that is running. That's why I fear its some kind of gas line issue.

Is this a gas company thing to diagnose or a heating/HVAC place? Thanks,
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Old 01-15-16, 12:24 PM
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I doubt you'd hear a pipe rattling.... especially a gas line.

I find it interesting that you hear the noise louder in the attic. That tells me that you need to get to the crawlspace soon and see what's happening in there.

It sounds to me like you may have two furnaces or possibly a furnace and an air handler sharing the same duct work and that you may be hearing some type of damper.

It's so hard to diagnose remotely like this. If you can't locate it you may need to call an HVAC company. Ask your neighbors who they use.

Just as an aside..... since you have four conditioning units you need to ID the units to see which one are heat only and/or heat and cool.
Old 01-15-16, 02:16 PM
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thanks for the note! just to be safe I called the gas company. no safety issues that they detect. they think its likely something bumping/rubbing/shaking/rattling against the gas line somewhere and the noise is radiating up along the gasline. could be anywhere in the system...will be very hard to find....but I guess I will have to ask an HVAC tech to look.

take care.

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