Lennox Pulse furnace problem

Old 09-21-11, 05:28 PM
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Lennox Pulse furnace problem


I just bought a house and as an HVAC tech I checked out the Furnace and Condenser before the home was bought. Much to my dismay, it was a Lennox. But it seemed to be working correctly. When I first switched the stat over to heating, I noticed the furnace made some clicking noises for a few minutes before it fired up. I didn't hear the normal sequence of events that come with most furnaces. But I was satisfied that it did its thing.
After moving in, I decided to check the gas pressure to make sure it was correct. But the furnace never came on. The stat was sending the call for heat and I heard various clicking coming from the unit, but the inducer never kicked on. I had to remove a heavy plate that was fastened with 6 bolts to even get to the inducer (which sat atop another device covered by insulation). Very bizarre component configuration.
I have voltage going to the inducer but it wouldn't start up. Just random clicking, which sounds like it's coming from the gas valve. Has anyone experienced anything similar or have any tips? Right now I'm thinking it's a bad inducer, but this thing is so complicated to what I'm used to (Goodmans) that I'm not sure..
Old 09-22-11, 04:56 PM
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Pulse furnaces are one of a kind. The heat exchanger need to be pressure tested every year by a Lennox tech. They are a positive pressure heat exchanger and actually use a spark plug for the ignition. Obviously if you have power to the draft inducer then I would say you need a new one of those. Parts are harder and harder to come by for that furnace. Below the inducer is the air flapper assembly, for maintenance purposes remove the 1/4" screws holding it on, Circular, Dont remove the middle screw yet. Now that it is off and in your hands, remove the middle screw. There is a nut on the back and you will have to hold it while removing the screw. BE CAREFUL! There is a washer in between the plates. Note where it goes! Now, remove the air flapper, Paper like circle with holes in it. Clean the air flapper with a clean cloth and reassemble. The air flapper maintenance as I have described is general maintenance, but has nothing to do with the problem you are having with the inducer not running. Sometimes the flapper will actually need replaced instead of just cleaned. DO not try to get to the spark plug and flame sensor unless you know what you are doing as they break easily! Let a Lennox PRO who knows the pulse furnace do that.

AGAIN, have the heat exchanger pressure tested! It is very important do to it being a positive pressure heat exchanger!

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