Turbine in my furnace?

[Mike Rocket J. Squirrel Elliot]

I've never had a house with air-conditioning before -- this is the first. I notice that the furnace makes a considerable amount of noise, of a type I am unfamiliar with. Maybe someone can help me understand what's going on.

Physical Description of system: forced-air natural gas furnace of the type I am used to seeing here in Southern California. It has air intake in the bottom, and hot air comes out the top which goes through sheet-metal ducting to registers throughout the house. Pretty normal so far. But above this furnace is another sheet metal box that that round ducting of the sort that Terry Gilliam put behind the walls in "Brazil" snaking off somewhere. Outside the house is a 2' x 2' x 3' metal cage with a circular grille on top and a fearsome-looking fan inside. I reckon this is some kind of heat exchanger.

Description of noise: With a "normal" furnace I expect to hear the gas valve open, a soft "whoosh" as the burner ignites and after some 30 seconds or so, the blower kicks in. With /this/ system, the moment I turn on the heat there is this jet engine whine that starts immediately and eminates from the furnace closet. The burner lights and after some

30 seconds, the blower turns on. What the heck is the jet engine whine?

[m Ransley]

It sound like you have a high efficency condensing furnace, the whine is a motor blowing the system clear.

[Bubba]

A motor, blowing the system clear? Ransley. Where do you come up with these terms? I believe you are talking about a Draft Inducer venter motor. It doesnt blow. It provides a negative pressure inside the heat exchanger. Is it a Tempstar, Keeprite, Heil, ICP furnace? How about a model and serial number? Bubba

[Edwin Pawlowski]

I don't know about the draft inducer on a home heater, but I do know a little about some gas fired boilers. Why is a negative pressure needed?

I'm licensed to operate high pressure steam boilers up to 300 horsepower. Any time the boiler is started, the blower comes on and there is a purge cycle. This is to clear the boiler and stack of any unburned gasses that may be in there. On modern equipment this is programmed into the controller, but on older systems it was done manually. Maybe Ransly knows about some home models that are similar.

[Mike Rocket J. Squirrel Elliot]

Oh, I get it: making me /work/ for my free advice! Well, I can play that game as well as anyone.

The furnace is labeled "Goodman Manufacturing Co," model GMP100-4 (rev B)

Mounted on the frontside, above the burners, is what appears to be a squirrel-cage blower about 8'' across in an enclosure. The input side faces into the furnace. This blower exits into a 5'' diameter round metal (galvanized steel?) vent pipe that vanishes up into the ceiling of the furnace closet.

When I turn on the heat, the sequence of events is:

WHIRRRRR (the turbine sound, comes from the squirrel-cage blower)

Tik-tik-tik (piezo starter) "Whump" (gas ignites)

Vwoooooom (main furnace blower pumping air into the heating ducts)

After a short bit of time, the small 5'' duct gets hot. What do I have here -- a furnace with a forced-air burner chamber exhaust? Never had such a thing before.

Oh -- I forgot. In the morning, shortly following the "WHIRRRR" of the small blower, you can hear the dead awakening and cursing the noise.

[Bubba]

Now that helps a lot. Oh, the free advice...............its not free. hehe. You thought I was goina tell you for free what people pay me for. Yur killin me man.....yur just killin me. Bubba

[George E. Cawthon]

Yep, it is the inducer fan, induces a flow of air through the burn chamber and up the chimney. Somebody did a very poor seal around that fan in my furnace and it caused the furnace to not operate correctly. (A safety feature is a pressure switch that needs a negative pressure to operate and maintain the burn). Just hope you never have to replace the little, noisy SOB. They will cost you upwards of $300. Glad I don't have a high efficiency water heater too. Sounds like you have an exceptionally noise furnace. The burner on mine makes way more noise than the inducer fan or the distribution fan. It is probably normal for your furnace. A few kinks (of the sound trapping kind)in your air system might be able to reduce noise distribution from your furnace.

[Mike Rocket J. Squirrel Elliot]

I've never had a furnace with an inducer fan. Was I just lucky? How does an inducer fan affect the performance of a furnace? I mean -- why the frick would someone want to mount such a noisy little bugger onto an applicance which up until now I considered a fairly quiet device?

The inducer fan's noise is not audible through the ducting. It comes right out of the closet. Which has a louvered door. Exactly NOT the kind of door I'd choose to use for sound-isolating.

[Mike Rocket J. Squirrel Elliot]

All right -- you outsmarted me. Go ahead, hold on to your darn advice. See if I care.

[m Ransley]

Bubba what the He## are you doing here if it is not for free helping advise? Your advise is worth nothing -zip-nada,as it benefits no one on this thread. You are worse than Dave or Stormin in this area, at least they try. Is it a motor blowing- blower motor- motor with blower-inducer-inducer blower- blower- . In the context of OPs question they are equal in my opinion.

[Bubba]

Whats wrong Ransley? Am I getting your panties in a bunch? Poor baby. You want me to get a pacifier for you now? Do you give out free advice because you cant hack it as a real service tech? I choose to get paid for a living an not subject the unsuspecting to harm and death. Ever read the caution and warning labels on something as simple as a circuit board change out? webtv..............that is just classic. Bubba

[George E. Cawthon]

Oh well, hell why didn't you say so. Oh, I guess you did. Why do you have a louvered door? Is it part of the air supply for the furnace. If not put something over the louvers. If it is, then put in a separate air supply or fix the louvers so that sound can't travel straight through.

The damned inducer is what you pay for having a higher efficiency furnace. Is it worth it? Probably not.

[HvacTech2]

Hi Mike, hope you are having a nice day

On 20-Dec-04 At About 00:00:01, Mike Rocket J. Squirrel Elliott wrote to All Subject: Re: Turbine in my furnace?

MRJSE> From: "Mike Rocket J. Squirrel Elliott" MRJSE> The inducer fan's noise is not audible through the ducting. It comes MRJSE> right out of the closet. Which has a louvered door. Exactly NOT the MRJSE> kind of door I'd choose to use for sound-isolating.

The louvered door is to allow for combustion air and is needed.

-=> HvacTech2

[BRIAN W GUNNING]

replying to HvacTech2, BRIAN W GUNNING wrote: Oh man, this whole string was worth the price of entry. Kudos to everyone who threw down for no reason at all.

I have two identical furnaces and we had the inducer fan replaced two years ago. Now /that/ furnace makes a great turbine like whine as it starts up, but the other doesn't. So I would cautiously offer than not all inducer motors are the same, and some may be more whiny than others. Our after-market one is WAY louder.

Solution? Just imagine you're jumping to light speed every time and it's really a nice sound effect to have in the house.

Par for the course folks.