Noisy Forced Air furnace

[jimy]

My wife and I moved to our current house about two years ago. I haven't had forced air heat since my college days, so I may be out of touch with how much noise is normal. When we bought it, an inspection was done and the furnace guy said it was fine other than a minor exhaust (chimney) fan noise which he investigated and stated "There is no reason for the noise" which was rather comical to me.

I do hear a little rattle when the exhaust fan kicks on, but when the main fan kicks on things get pretty loud - although no funny noises. It certainly dominates whatever minor noise the exhaust fan makes (dunno if the exhaust fan runs whenever the burner is on or if it is just on to get the things warmed up and rising in the chimney), If we are watching TV we have to play with the volume as the furnace cycles on and off. The furnace is natural gas.

Now I believe at least part of the problem is that the home was built in the 40's and the basement furnace is directly below the center of the home and feeds old fashioned 12x14 wall vents for three rooms. The duct work run to each of these three rooms is a couple of feet from the furnace at the most. So I suppose that is pretty much worst case for getting furnace noise upstairs.

There are runs going to various other places in the house and the duct work all looks much newer than the 40's. The other rooms in the house are much quieter and have much smaller, more modern vents. But as a whole the ductwork probably was done piecemeal and may not be optimal. We are generally happy with the heat distribution - no super cold spots.

The furnace is a Heil and is perhaps 20 years old. I don't think we would replace it just because of the noise, but it sure would be nice if it was quieter.

1 - Assuming the main fan is working normally, is there any chance a quieter one is available? Or is it mostly just the CFM of airflow rather than the fan/motor?
2 - Is a new, modern furnace going to be quieter or is this just the way it is going to be?
4 - Anything I might be missing?

FYI - I just looked up the serial number and this furnace was manufactured in 1996

thanks,

Jim

 

[Showkey]

25 years old……….that’s getting close to end of life.
Does not look like any parts were removed. Did they inspect the exhaust blower for rust debris rattling around in the squirrel gage ?

Not related to the noise……….That vent pipe rust inspected and solid metal ?

A new 90plus efficiency two stage are so quiet its hard to tell if they running.

 

[nadogail]

Your sheet metal parts might be "Oil Canning". Rattling like a drum. Sometimes they can be mechanically dampened.

 

[jimy]

It is good to hear that a modern furnace would likely be much quieter. I may get someone in here for advice and an estimate. We won't plan on replacing it this year but it would be good to have some idea of our options now, rather than make a quick decision when it goes kaput.

thanks...Jim

 

[unslow1]

My Carrier furnace installed last month is much louder than the 35 year old one they took out. After searching the forums that is not uncommon so don't count on the new one being quieter.

 

[Bert_]

Does it just sound like fan noise? How big is the furnace and how much / size is the ductwork?

Undersized ductwork will be loud. A newer furnace could actually be worse in that respect, 90+ efficient furnaces need more airflow than an 80%.

 

[Showkey]

Does it just sound like fan noise? How big is the furnace and how much / size is the ductwork?

Undersized ductwork will be loud. A newer furnace could actually be worse in that respect, 90+ efficient furnaces need more airflow than an 80%.

Not sure where that comes from………on low heat stage one standing next to the furnace you can barely tell if it on and upstairs you can not detect any noise. The t-stat click noise is only clue.

On high heat makes about the same fan noise as the AC cooling. Noticeable yes, objectionable no.

25 year old 2 stage that was replaced the draft inducer motor made more noise than the main fan on low heat.

 

[Bert_]

Not sure where that comes from………on low heat stage one standing next to the furnace you can barely tell if it on and upstairs you can not detect any noise. The t-stat click noise is only clue.

On high heat makes about the same fan noise as the AC cooling. Noticeable yes, objectionable no.

25 year old 2 stage that was replaced the draft inducer motor made more noise than the main fan on low heat.

Most around here are single stage, so there is no low fire, but that would definitely reduce noise.

None of this is a problem if you have adequate ductwork, but there's a lot of houses that don't. Restrictive ductwork will make any system noisy. High efficiency can often make it worse because it needs more airflow.

A high efficiency furnace needs more airflow than 80% because it's rated for less temperature rise.