Excessive Ash Buildup in Heat Commander Burn Tubes

[Citationls]

Hello again, I hope I'm not creating a redundant post. I was surprised to find lack of info when I used the search function for this issue.

I seem to be having excessive ash buildup in the exhaust tubes of my Heat Commander and I'm wondering what the cause may be.

I've had my Drolet Heat Commander for almost a couple months now and I love it. I inspected the burn tubes after burning continuously for the first two weeks and they looked relatively clean with a little creosote buildup.

Since then, I've been using the Heat Commander on and off for a little under a month. The weather keeps getting warmer so I've had more cold starts than I had during the first two weeks of use. It is also definitely harder to establish a good draft when the weather is warmer (over 50F) so the cold starts take a little longer to get up to temp, meaning more smoke for longer on startup. However, I'm getting better at cleaner startups.

I did burn about one full firebox full of what I believe to be some sort of pine 4x6s that were 10 to 15MC. I didn't burn any more of them because they produced excessive ash that floated out the door when I went to reload the stove. I like to keep things clean so I wasn't a fan of the messy ashes floating out.

I have also been using small, dry, pine pallet pieces to start my fires because they burn fast and hot. I've been doing that since day one though.

Considering I only had creosote and little to no "ashes" in the burn tubes when I inspected them after the first couple weeks, it seems weird that there is so much "ash" in the burn tubes after checking them a month later.

Any ideas what would cause this? Possibly the pine? Or would it be more cold starts? Or is this normal? I also included pics of the stove pipe by the barometric damper. Ignore the ashes in those pics, they are from putting a piece of newspaper in there to establish draft so I could clean out the stove without a backdraft.

Furnace is installed in basement of 2 story house. Barometric damper set to .06. Figure lower setting would introduce more cold air meaning more creosote.
Wood is all around .15 to .20MC on average. Not ideal, will be better next year.

Sorry for the lengthy post and thanks for reading.

 

[sloeffle]

Had a Caddy ( same firebox design ) for 10+ years and I never saw ash like that in the heat exchanger tubes. The ash that was in the tubes on my Caddy was like dust. Was diligent about cleaning them out every week though. The more ash you have in the tubes, the less heat is going into your house.

A few times I would get creosote in them if I was burning less than ideal wood but the creosote would burn off once I got back into dry wood. I burn mostly ash and I've seen some pretty big clinkers ( look like rock ) left in my firebox in my OWB and Caddy before. That's almost what it look like but it's made it into the HX tubes. Spit balling here, I wonder if the ash has clumped together due to the pitch in the pine. If I was to guess, I'd say it's due the pine.

• Do you get the same ash buildup in the HX tubes when you burn all hardwoods ? If you don't have any hardwood, throw a FEW bio brick in with your load and see if you continue to have the same issue.
• Any idea what your exhaust temps are ?
• Have you called PSG to get their opinion on the issue ?
• I'm not sure if the Commander has the baffle board on top of the burn tubes inside of the firebox, if it does, is the baffle board pushed all the way to the back ?
• Do you see fire coming out of the burn tubes in the middle of a burn cycle ?

 

[Citationls]

Had a Caddy ( same firebox design ) for 10+ years and I never saw ash like that in the heat exchanger tubes. The ash that was in the tubes on my Caddy was like dust. Was diligent about cleaning them out every week though. The more ash you have in the tubes, the less heat is going into your house.

A few times I would get creosote in them if I was burning less than ideal wood but the creosote would burn off once I got back into dry wood. I burn mostly ash and I've seen some pretty big clinkers ( look like rock ) left in my firebox in my OWB and Caddy before. That's almost what it look like but it's made it into the HX tubes. Spit balling here, I wonder if the ash has clumped together due to the pitch in the pine. If I was to guess, I'd say it's due the pine.

• Do you get the same ash buildup in the HX tubes when you burn all hardwoods ? If you don't have any hardwood, throw a FEW bio brick in with your load and see if you continue to have the same issue.
• Any idea what your exhaust temps are ?
• Have you called PSG to get their opinion on the issue ?
• I'm not sure if the Commander has the baffle board on top of the burn tubes inside of the firebox, if it does, is the baffle board pushed all the way to the back ?
• Do you see fire coming out of the burn tubes in the middle of a burn cycle ?

Ok, so sounds like it isn't normal. I've been burning red oak since I got the stove. It seems like I may have been using the wrong terms for burn tubes. Are burn tubes where the secondary air goes into the firebox? If so, yes, I do see flames coming from the burn tubes often, it looks like flames coming from a propane grill. I will check the baffle board next time the stove is cold. I have not contacted the manufacturer yet, wanted to verify with you guys that it isn't normal first. Exhaust temp on magnetic guages placed on the exhaust tube clean out door usually read 200F to 275F depending on heat demand. I haven't tried a biobrick yet but will certainly consider it if the issue persists.

One thing I did just think of with your mention of pine resin potentially causing sticking is that I do tend to have a slight downdraft in the flue. We've definitely had some damp days due to our lack of winter and surplus of warm, rainy weather here in Connecticut. I noticed when I cleaned the ash drawer out today that the ash seemed a little damp. Not wet or sticky, just not super dry/fluffy and dusty like it normally is.

Now I'm wondering if the combination of the downdraft/backdraft when the stove isn't in use and the damp weather is causing the exhaust tubes to get slightly damp when not in use. Then when I use newspaper to start the fire, the burnt pieces of newspaper are floating up through the damp exhaust tubes and "catching" or sticking to the slightly damp surfaces of the exhaust tubes, leading to this weird ashy buildup. Seems like a bit of a stretch but not sure what else it would be.

 

[sloeffle]

Are burn tubes where the secondary air goes into the firebox? If so, yes, I do see flames coming from the burn tubes often, it looks like flames coming from a propane grill. I will check the baffle board next time the stove is cold.

If you are seeing flames from the burn tubes that means your wood is dry and it's off gassing correctly. These furnaces don't really burn the wood, they bake the wood at a low temperature which causes the wood to make wood gas, and then what you see being burned by the secondary burn tubes is the wood gas being burned off. That's why you get a lot of coals too.

Wood gas - Wikipedia

en.wikipedia.org

When I would do a cold start, I would actually put a lit piece of paper in my baro to get the draft moving in the right direction. Most of the time it would be okay but more than once it would draft back into the house if I forgot to do it.

Are you using a 6" SS flue, and if so, are you following the 3/2/10 rule ?

 

[brenndatomu]

To me I don't see anything to get too excited about...does look like you need to clean the HX tubes more often though...it is SOOO easy to clean those SBI furnaces, do it weekly, I did...I miss the ability to clean in a couple minutes like that now!
Cold starts cause more buildup, period.

 

[Citationls]

Ok, thanks for the wiki link/info. It sounds like it isn't too big of a deal and may be due to my increased number of cold starts and lack of cleaning. Thanks for the help!