Mini-Puffbacks: Consult Please

Reporting back on my experiment to put a small piece of coal--similar in size to the one I found--under the hopper gasket to see if I could replicate the puffing---Nada. Quiet, even burn with no signs of the earlier phenomenon. I am resolved to wait and see if I see the puffing again, then experiment to try to learn more. Merry Christmas!!

Be carefull. a coal fire follows the air. If you intentionally leave an air gap under the hopper lid on your stove, you will be allowing fresh air to enter the hopper, and the fire will travel up into the hopper.. causing lots of potential problems,, like warping the hopper, overheating the stove etc etc..

We have a forum member with a Hitzer 503, in western Michigan, near the lake, he has constant high draft.. His hopper lid gasket was loose and he had some fines holding the lid up a little bit.. he had the fire burn several inches up into the hopper,

So be carefull with your experiment..

As long as the mini-puffbacks and small,, just think of it as your stove muttering or snoring..

Greg L

LsFarm, good point about being careful. I will monitor and learn what I can. About the muttering and snoring, these are things I am getting used to, but I sure do appreciate the steady, even heat these days and with a major snow storm approaching.

You might try the opposite approach,, make sure the hopper lid is clean, the gasket clean, and set something heavy on the lid, to help it seal better, and see if that lessens the 'puffin'.
You might be getting a slight amount of fresh air past the lid and seal,, just enough to cause the 'puffin'.

Greg L

Update on the puffback issue. For the past several days and since my last post, no puffbacks. I have been examining the hopper door and sealing area. I made sure everything was very clean so that I got a good seal. Last night, my puffback friends were back. I noticed that this occurred after the stove had been burning since the morning and in a stable way. I decided to open MPD and ashdoor to "goose" the fire to stabilize at perhaps 100 degrees higher than it was to get some last bit of warmth out of it before I shook grates and added more coal for the evening.

After letting the temperature come up, I closed the MPD and ash door, leaving vents just as they had been set previously for the day-long burn. Very shortly thereafter, I saw about 4 puffs like those portrayed in the video I posted at the beginning of this thread. This time, I did not disturb the fire in any way and just watched. They soon stopped and the fire stabilized. I later shook grates, added coal, and got the stove set for the night. While doing this, I examined the hopper door and seal--clean as a whistle and no air getting in that way.

Working hypotheses at this point: 1). puffbacks not related to air getting in through hopper door area. 2). mini-puffing phenomenon caused by hot fire heating unburned coal in hopper, thereby producing volatile gases that eventually and periodically "spill under" the bottom of the hopper apparatus and then ignite. 3). puffbacks stopped when fire stabilized at a slightly lower fire and with less available air after I closed MPD and ashpan door.

I will continue to observe and further refine my understanding of this interesting phenomenon. Any other Hitzer 503 owners seeing what I am seeing?

Anything happen if you just open the hopper lid then immediately replace it? Any effect of disturbing/poking the coal in the hopper (from above, thru hopper door) without causing any to fall into the firebox or even affecting the fire itself at all?

Maybe, as coal drops onto the fire right below the hopper opening, as volatile gases are relased they go directly upward to collect in the free space in the hopper above the level of coal remaining in the hopper. As that gas pocket enlarges, it becomes big enough to be ignited by the fire.

Dean at Hitzer might have seen this before--you could email him and send a link to your YouTube video.

I will email Dean with a link to this thread. He might have some experience with this. Will report back after I hear from him. --thanks

I had a detailed correspondence with Dean at Hitzer regarding this puff back problem. He had many helpful comments regarding possible variables that could contribute to the puffing problem, but I think the main point I took away from our correspondence is the possibility that the increased volatile gases with my Superior coal might be a significant factor. When I recently burned 1000 pounds of Blaschak coal I don't recall having this problem.

Also, he told me about a past situation in which a "bad load of coal" --type unknown--caused some puffing problems that led to several consumers calling their coal dealer and ultimately the coal was replaced. This raised the possibility in my mind that coal with increased volatile gases might be part of my problem.

He also suggested that I keep the over-fire vent, intended to wash the inside of the glass on the door, open to increase the amount of air available in the firebox. I will continue to monitor my stove throughout the rest of this season and next year I might switch to Blaschak. As always, Dean was very helpful.

It's great to hear about a company that works with customers well.

Can you imagine the people at Harman ever interacting with a customer?!?!?!?! My impression from personal experience is that they go out of their way to avoid customers after the sale!

On Saturday, I had 4 tons of Superior nut delivered to prepare for next season. Given my experience with mini-puffbacks, I had considered other coal, but went ahead with Superior. I casually mentioned the puffback issue to my dealer, who surprised me by saying he had gotten reports from several of his customers last winter about this issue and that the customers who were reporting were not all using Superior. He commented that he investigated this and concluded that the amount of oil he added to the coal to keep the dust down might have been a problem. He had been using 1.5 gallons of oil per ton, but then cut this back to 1 gallon or somewhat less in an effort to correct the problem. After doing this, he says he had no more reports of puffbacks from customers who got subsequent deliveries of this coal with less oil.

Might this oil issue have caused my puffback problem last winter? This winter's burn with the less-oiled coal should tell the tale. I will report back....

I think that the stove is starving for top air to burn volatile gasses, and is pulling harder through the under air, and it can't get it because of the hitzer temp control therostat (more under air higher temp). So they build up and puff and build up and puff ( just my guess). With superior you do have to watch for gasses. IT is a tad gassier than others it seems, but i have good luck with this brand. It is a good value for the dollar with my dealer.

Another option you could consider and I'm not sure how feasible it would be for you and your stove layout would be a draft inducer. Tjerlund makes one that goes on your stove pipe just above your stove that you could turn on when you recharge the stove and turn off when everything gets to temp. That'll help to evacuate the buildup of gas out of the stove. You may also lose some heat too but since you can turn the inducer on and off it shouldn't be too much of an issue.

I was having the same issue after I reconfigured my piping on the DS this past winter. I ended up buying the AD-1 draft inducer I just mentioned; though I'm still undecided if I'm going to actually use it or not next winter.

Good ideas and feedback on this issue. I am hopeful that the change my coal dealer made--putting less oil on the coal--will reduce volatiles and solve my problem. That would be sweet! I will provide feedback on how things are going after the heating season gets underway.

Final Report on this mini-puffback issue. I think my coal dealer Vern identified the source of the problem when he and I had a lengthy chat this summer while he was delivering 4 tons of Superior nut. This is the same coal size and source as last winter when I had the puffing issue. His commented that he thought the problem was from too much oil (about 1.5 gallons/ton) and said he heard from other customers with similar complaints. I concluded last summer that I would wait to see how the new coal burned now that he said he was adding only 1 gallon or less of oil/ton.

I am happy to report absolutely no puffing from this year's coal. I am forced to conclude--happily--that Vern was correct. Anyone else who ever has this mini-puffback problem should move possibly too much oil on the coal to the top of the list of probable causes.

Wishing everyone safe and steady burns!

Outstanding BEEMAN.