# Loud, low toned hum from high efficiency furnace.



## SKIP4661 (Dec 3, 2008)

That noise is normal with the pulse furnace. it is a good furnace but loud. Also heat exchanger issues are common with this furnace. May want to have it inspected.


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## Yoyizit (Jul 11, 2008)

SKIP4661 said:


> That noise is normal with the pulse furnace. it is a good furnace but loud. Also heat exchanger issues are common with this furnace. May want to have it inspected.


What is the 
"small round metal muffler looking part" and 
how is it making that noise?

http://www.inspect-ny.com/heat/lennox1.htm


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## sktn77a (May 11, 2009)

The droning noise is basically a single cylinder internal combustion engine in the Pulse furnace! The muffler damps the noise down somewhat. These were the "buzz bombs" of the mid 80s and famous (infamous?) for this noise. Isolate the furnace from the house so that vibration isn't transferred directly (compliant stand, flexible plenum coupling, etc) and that's about all you can do.

If you have an additional noise that goes away a minute after the furnace starts up and doesn't continue while the furnace is heating, it could be the induced vent motor about to give up the ghost.


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## yuri (Nov 29, 2008)

Get a Lennox tech to thoroughly check that furnace. The air flapper membrane in that "object" of yours may need replacing. The gas pressure should be checked and Lennox recommends the heat exchanger be pressure tested every 4 yrs. That furnace is like a Porsche and very few people know how to fix it properly. I know them well, started installing them in 1980.


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## Ryan C (Oct 15, 2009)

Thanks everyone for the help. I am going to get someone to come inspect it very soon.


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