Solution for furnace knocking...

[snfexpress]

As some of you may know, I had to remove the furnace last winter to get it fixed. Well, in the removal and re-installation process, I must have done something that caused the furnace to start making knocking noises.

These noises were a consequence of thermal expansion and contraction of the exterior metal skin. My solution? Eighteen inch long pieces of angle aluminum and some epoxy. I glued the angle aluminum to the exterior skin where I could push it in (slightly). Now, the skin is rigid and no more noises.

[Ozz]

Good job, Michael.
Generally that noise is called 'oil canning' Common in sheet metal, they break support creases in it to keep it from doing that, you made a good field repair.

[snfexpress]

Ozz,

Thanks - didn't know the proper term. Before I took out the furnace, I cut a part of the outer metal enclosure to try to get a new circuit board in, hoping that would be the cat's meow. As it turned out, I needed to replace the electrode, requiring a total removal of the unit. I riveted the cut that I made, but this must have been the cause of the "oil canning".

[scductman]

Ozz is right we have to brace our big duct systems. They can sound bad in a ceiling if you dont. bobby