Lennox Traditions T300P Rumbling Sound

[kplmn]

I just purchased and installed a used Lennox Traditions T300P pellet stove. I think it’s a great looking stove; it's in great condition and seems to work fine, except when heating, after the combustion air blower slows down, the stove makes a loud rumbling for 2-3 minutes. This is probably 8-9 minutes after the stove turns on. It’s not the combustion or convention blowers, they seem to run smoothly. It’s a loud, lower rumble sound that can be heard upstairs in the bedroom, with the stove on the main floor below. When I open the front door ever so slightly, the sound stops. If I close the door tight again, the sound returns. It only happens for a couple minutes during each heating cycle. I have played with the draft control and it doesn’t seem to make a difference all open, in the middle, or closed. I have cleaned the stove well and it does seem to help a little, though not eliminate the sound. When the stove goes a few more days between cleanings, the sound does seem to get louder. To me it seems like the stove is wanting for more air. Any ideas? Any thoughts would be helpful. Thanks. KL

 

[Delta-T]

might be part of the chassis/body vibrating until it heats up, expands and stops. check the trivet on the top when that happens, and just go around touching the body to see if you can make the sound stop. wear a glove, part of the body get pretty warm. the ash pan has a funny latch thing i think and the flat ash pan could vibrate pretty freely and make some noise. noises are so challenging to troubleshoot sometimes, especially over the internet

 

[kplmn]

I have touched and fiddled with everything that I can touch, and I haven't been able to isolate the sound. To me, a non-professional, it sounds almost like a vacuum is created as the heat really starts going up the exhaust. The sound is almost like a diesel truck idling outside the house. I have opened and closed the ash pan while the sound is happening, and it doesn't really change the sound. I thought the house might be too tight (I did put a 3" fresh air intake int he basement last winter), but I have opened a window in the same room with the stove and it doesn;t seem to change the sound. Is it possible the path of intake air from the small damper below to the brun pot has an obstruction? Or, could the path of air up and over the heat exchanger be blocked somehow? Thanks. K

 

[Delta-T]

just about anything is possible. take out the firebricks (carefully of course) and open up the channels on the side of the combustion chamber to look for obstructions. you might need a coat hanger or some other long flexible thing to break up any mass that has accumulated in the passages from the combustion chamber to the exhaust flange. it can be difficult to get behind the HX tubes, but that same coat hanger can be good for that. there a piece of gasket around the damper plate that can get funky too. I usually associate low rumbling to the auger motor, but you say the sound is continuos for 2-3 minutes? I dont think the auger runs continuously for 2-3 minutes, so I'm stumped.

 

[Wood Heat Stoves]

start with all the basic svc, then see whats going on...
need a copy of the svc book? shoot me a pm with your email
dave

 

[kplmn]

Well--I went back to the manual and read about adjustments to the stove. I re-read the section about the damper and then moved it all the way to the other end. Surprise--the rumbling has decreased about 95%. I think I had the damper all the way closed rather than all the way as I had previously thought it was. The flame burns very bright and tall, so I plan to try closing the damper a notch at a time to see how it behaves, but I thnk I've found the problem. Thanks.

 

[Wood Heat Stoves]

glad it was a simple fix

 

[kplmn]

Well--not so fast. I moved the stove to the other side of the house, to a new horizontal thru the wall vent. The rumbling is still present, but no the draft is terrible. The stove smokes us out between cycles as it relights. I broke the stove down and cleaned out everything. I did find the back passages of the flue behind the firebox are not accessible by any means. I used a coat hanger and was able to insert a vacuum hose in the exhaust through the combustion fan house, but it's not great for cleaning thoroughly. Anyway, I found the manual damper was only opening about 60%. The additional 1.25" or so was binding so bad that it would not open. Some WD-40 and gentle prying with a hunk of wood unbound it, and now it moves like it should. I just put it all back together and no smoke out on refiring. I like it. I still do not like the lack of access to cleaning the flue. I'm considering cutting a circle in each side on the back of the firebox to insert a vac into the flue. I'd have to fabricate a couple access plates to cover the holes, but new stoves seem to have the same access holes in the fireboxes. I'm also thinking about selling this Lennox T300P and buying a new Bosca Spirit 500 that a local dealer has and will sell at a great price (plus I get a direct 30% tax credit). Any thoughts about all this out there? Thanks. K in the UP of MI (245" of snow last year).

 

[krooser]

Use a leafblower to suck out all that hidden ash....

http://www.youtube.com/watch?v=aLRfu4WNaR8

 

[pastera]

I have the same stove - it's great looking but pretty brain dead on the controls side. Good news is the controller is a PIC16f877 and I will be updating it to have a high/low thermostat burn mode to save the ignitor.

If you are getting a smokey startup and need to open the damper over half way then the stove is clogged up somewhere.

Pull the combustion blower - you will need a 12-15" extension to reach the three nuts holding it in.

With the blower out

The damper should just fall out - clean it and it's mating surfaces. Most likely there is a lot of carbon buildup that is causing it to stick (did on mine when I bought my house - stove was filthy)
Clean out the blower housing and wheel. Vacuum the dust out of the motor internals (best effort don't stick anything in there).
Scrape down the exhaust passages as much as possible from the rear through the damper opening - no need to vac if you have a leaf blower

Reinstall the blower and open the damper fully

Remove the burn pot, heat exchanger baffle and the firebrick

Vacuum out the igniter tube - this is very important if you are getting slow, smokey startups. Ignore it and get ready for a new igniter ($120 and a few hours work)
Pull the tube scraper up, brush and vacuum the bottom of the tubes. This area is very hard to clean if the fire brick is in place
Stuff a rag in one of the exhaust ports at the bottom of the heat exchanger tubes.
With the door open, run the leaf blower cleaning until the air is nice and clean.
Swap the rag to the other exhaust port and repeat the leaf blower trick.
Pull the rag, close the door and hit it with the leaf blower again

Reassemble completely and set the damper to three notches open from fully close if you have a short horizontal run or five if the exhaust is long.

Check the door and window gaskets - a leak here will cause the burn pot to starve for air and could be causing the smoke to start a secondary combustion in the hot exhaust passages. An uncontrolled combustion could cause a rumbling

Startup and let the stove get up to temp on medium - once the stove is up to temp adjust the damper so that the smaller coals just start to 'dance' when new fuel is dropped

Aaron