Banging heat exchanger

John Mills_5

Thanks, Randy, that did the trick. Took 3 tries but when he asked the lady if she heard it anymore, she said heard what?

John Mills_5

Scorched air

11 year old Ducane oil furnace, heat exchanger and chamber gone from no maintenance. We cleaned everything, changed the exchanger which included new chamber, serviced the burner, firing at the lower of 2 firing rates. After running and just after the burner stops, the heat exchanger lets out a big bang, like a sledge hammer on an old drum. Tried another heat exchanger, same thing. Temp rise below maximum, stack temp a bit high to get 0 smoke, otherwise all looks fine. It has been suggested to yank the blower wire and let it cycle on limit a couple of times and that should stop the kaboom. Anybody heard of that remedy or heard of problems with new Ducane heat exchangers?

Timco

After burner shuts down, but while fan is still running? Mechanical boom (like a hammer hitting it)or like a small explosion boom (softer)? Gas valve not closing all the way when it shuts down, buildup ignites?

Tim

John Mills_5

hammer

Sounds like a big hammer smashing into the heat exchanger. It is an oil burner!

Ed_26

hx noise

Intertherm/nordyne once told me to find the approx. spot where the hx was flexing, & 'peen' it there. Maybe this will work for you. (if all else fails, use a bigger hammer)! Might be worth a try.

Randy Berg_2

Try this

diable the blower motor, run the burner and let it cycle on high limit, let the unit cool on its own to ambient, reconnect the blower cycle and see what happens, if it still cannon's recycle again as stated above. Had this problem on a 3 millon btu oil fired air rotation unit, and their rep told me to try this, and it worked, hope this helps,