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Hello - just found this forum - very interesting

My house was built in 1979 and I have an AH130 furnace from Airco Products of Vancouver. It has been working fine but recently developed an intermittent vibration noise that wakes people up in the basement bedroom next to the furnace room.

I have taken off both front panels to see if there was anything loose and to reinstall the panels tightly. I have pulled out the fan and motor and put a few drops in to both ends of the motor.

Does anyone have a probable suggestion what the noise may be?

Can anyone recommend a service person who works with Airco furnaces all the time?

How long do these furnaces last - some people say this is a very durable furnace that will out last the new furnaces ??

Should I be thinking of replacing it - if so what HE type can you suggest ?

Many thanks Bob

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I'm not familiar with Airco products so I have no comment about how long they last.

For the noise, check your supply and return registers. They sometimes loosen and rattle.

If that's not it, tape over the interlock switch and run the furnace with the blower door off. See if you can figure out where the noise is coming from. It sometimes helps to use a dowel to press on various parts of the blower assembly - the motor, the mounts, the shroud, etc, to see if that makes a difference to the noise.

Pay particular attention to the mounts on the blower wheel. These sometimes have rubber bushings, which might have worn through or fallen off. Alternatively, there are other mount designs that crack over time, causing a rattling noise.

If you can't find anything that's loose, the blower wheel bearings or bushings might be bad. It's also possible that the blower is no longer balanced.

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I'm not familiar with Airco products so I have no comment about how long they last.

For the noise, check your supply and return registers. They sometimes loosen and rattle.

If that's not it, tape over the interlock switch and run the furnace with the blower door off. See if you can figure out where the noise is coming from. It sometimes helps to use a dowel to press on various parts of the blower assembly - the motor, the mounts, the shroud, etc, to see if that makes a difference to the noise.

Pay particular attention to the mounts on the blower wheel. These sometimes have rubber bushings, which might have worn through or fallen off. Alternatively, there are other mount designs that crack over time, causing a rattling noise.

If you can't find anything that's loose, the blower wheel bearings or bushings might be bad. It's also possible that the blower is no longer balanced.

Jim-he does not need to worry about the interlock switch-it will not have one.

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  • 8 months later...

Howard Pike is the man, Airco furnace expert.

Chimo Furnace Service in Coquitlam.

He will be posting here shortly to tell you all about your furnace. You should post the Serial #

Thanks for the vote of confidence, John. I've got a new computer and a sick old one. Sort of lost TIJ through the transition.

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  • 1 month later...

Airco furnaces that were built from the early 1970's until 1985 used steel ribbon burners fabricated from slotted steel pipe and pressed venturi. They were great for natural gas but never worked well enough for propane. They howled.

Gas burns, but not like the flame of a candle. As the gas (actually, the gas-air mixture) blows out of the burner, the flame runs down the gas, consuming as it goes. When everything is balanced, the flame consumes the gas at the same rate that the gas flows from the burner, and the flame appears to sit on top of the burner. However, on Airco's steel burner, the venturi effect was too efficient and drew in too much air, causing the velocity of the gas to exceed the rate of combustion. In effect, the flame would momentarily lift from the burner and then jump back onto it as the gas-air mixture further mixed with more air, moving it into the range for combustion.

This is no big deal, as it happens intermittently on all furnaces. We all know that gas burner flames are erratic. The problem with the Airco steel burner was that it could be tuned - the air shutter opened up - to get the flame jumping at a regular frequency. And, to make matters worse, at a frequency that was in harmonic to the height of the heat exchanger.

The flame would lift and jump back, sending a pressure wave up to the top of the HX, which would then reflect back, hitting the burner in time to augment a subsequent lifting/jumping of the flame. This quickly turned into a very loud trumpet blast that became known as the "Airco Howl".

It is a minor problem that is easily caused by giving the burner too much air, and easily fixed by adjusting each air shutter closed, and then opening it until the yellow flame just disappears, PLUS a little bit more. Don't ever operate an Airco furnace with closed air shutters - it will soot up in a few hours of operation.

The usual problem found in the field is the air shutter slowly increasing its opening over years of operation. It will then cause the Airco Howl on start-up when the burners are cold.

The fix is to close each air shutter somewhat, while avoiding the yellow flame.

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Thanks howardpike !!,for such a nice information about airco furnaces.But,does this problem comes in every model of Airco furnaces or in selected one's.?

Basically, yes. From the introduction of the "steel burners" in the early '70's until the last "Airco" was built in 1986 - the Highboys, Counterflows, and Lowboys; the standard and mid -efficiencies - whatever was built to burn natural gas with the steel burners, had the potential for the Airco Howl. The cast iron burners weren't affected.

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