Furnace Making Loud Noise

A boom at ignition or a grinding blower means a component is working under stress it wasn't built for, so call before it lets go.

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When this becomes an emergency

A deep thump or boom rolls through the ductwork the moment the burner lights.
Something is screeching or grinding near the blower housing.
A rattle builds as the unit runs and quits the second it shuts down.
Neighbors upstairs can hear the startup through the floor when they never could before.

What a pro does

Noise is a diagnosis, and the kind of noise narrows it fast. That thump at startup is usually delayed ignition, where fuel pools for a second before catching, and every one of those small explosions punishes the heat exchanger a little more than the last. Screeching normally comes from dry blower bearings or a belt gone slack. A tech listens at each component through a full cycle instead of taking the sound apart from a description. Sheet metal panels and duct takeoffs buzz at particular speeds, and that's the cheap thing to rule out first.

Frequently asked questions

How worried should anyone be about a thump at startup?

It deserves attention. Repeated delayed ignition works cracks into a heat exchanger over time, and a cracked exchanger is a combustion safety matter rather than a noise complaint.

Why does the racket seem worse in an old house?

Century-old framing and long duct runs carry vibration a long way, so a modest mechanical noise in the basement can arrive at a bedroom sounding much bigger than it is.

Can a rattle be nothing?

Sometimes it is exactly that. An unseated access panel or a loose duct joint buzzes convincingly and goes silent once it's fastened down properly.

Should the system keep running until someone looks at it?

Letting it run long enough to describe the sound accurately helps, but a fresh grinding or booming noise isn't something to live with for a week.

Furnace Making Loud Noise?

Get connected with a local pro now.

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