Albie's Corner

Masonry heater smoking? It may not be what you think!

By January 26, 2015 No Comments

December 1, 2014
I was working on a masonry heater project in Pittsfield, Massachusetts in October (2014) when I received a call from my old friend Peter Moore in Vermont.  Peter, who builds exquisite masonry heaters and wood fired ovens (for 30+ years), was reaching out for help.  He had built a masonry heater for his daughter and she recently discovered that the heater was not drafting properly and was smoking into the room.  Peter went over to inspect everything in the heater – checked the dampers, soot doors and channels finding no blockages or open doors anywhere.  There appeared to be adequate combustion air.  Nothing that he tried to do helped the situation and the heater continued to smoke without any explanation as to why.  He was at his whit’s end and was both puzzled and genuinely concerned.  I told Peter that I did not know precisely what the problem was, but I knew it had to be either inadequate combustion air or a blockage somewhere in the system.  I said that I could share some smokey heater stories with him and perhaps my stories could provide him with some clues to eventually unravel his own smokey mystery.
I recalled the time that the owner of a ten year old double stacked heater (one in the basement and one on the main level) had called with a smoking problem with the basement heater which had always worked perfectly.  The house was only an hour’s drive from home so I said that I would like to come over and inspect.  I looked at the upstairs heater first and found everything in good working order.  The soot doors were tight, the channels were clean and the dampers functioned properly.  I did not try to light a test fire.  Downstairs in the basement, I went through the same drill; everything on the heater seemed to be in place, clean and operating correctly.  I then turned to the chimney to inspect it through the clean out door mounted at the base of the chimney.  The clean out door for the upstairs heater revealed no obstruction in the chimney but the clean out door for the downstairs was a different story.  Jammed tightly into the base flue tile exit from the heater into the chimney was a dead wood duck which had fallen 36+ feet down the chimney to the bottom where it couldn’t get out.  Wood ducks like to nest in hollow trees or wooden boxes so it may have found the top of the chimney inviting, but once in, gravity overcame curiosity and the wood duck fell to the bottom.  Chimney swifts are better adapted to life in chimneys and have little claws on their wings which help them climb out but nothing the wood duck had could let it escape.  I pulled the lovely male duck out and assured the owner that the heater would now resume working well.
I mentioned to Peter about my clients Roger and Ann, whom we had built a split face soapstone see through masonry heater with wrap aroundPizza Stone in Bake Oven-1 heated benches during an eight day power outage on a windy lake shore in Western Maine.  After a few very successful seasons of using the heater on a daily basis, I got a call from Ann (who was home taking care of two young boys and the hearth), saying that her recently lit heater was smoking.  I asked her to go carefully through the drill of checking all the dampers and soot doors including the chimney clean out in the basement to see that they were all closed and that the dampers were in the correct operating positions and she assured me that they were.  On my job in Pittsfield, Maine and it was nearing the end of the work day so I told Ann that I would head West towards her house immediately.  She lived about one and a half hours away.  As I approached my home in Norridgewock, midway on my journey to her house, I got another call from Ann saying that she had found the cause of the problem and fixed it.  Her partner, Roger, had always cautioned her to leave the upper chamber bake oven door closed once the firing process was underway, but after trying out all the other options with no luck in solving the smoking heater issue, she decided to open the oven door, and there perched nicely on top of the smoke throat in the floor of the oven, was the pizza stone that they had used the previous night and forgotten to remove after the pizza baking was done. She reached quickly in with a gloved hand, removed the pizza stone and everything worked perfectly again. The smoking stopped and I did not have to continue my drive beyond home.
I then reminisced about the story of the architect/builder/sailer and his wife in New Hampshire who had me build a double stack heater for them.  We finished the heater before the house was done and as the house neared completion and the weather started to turn really cold, the owner decided he needed to take a break and headed to warmer climates for a solitary sail to unwind a bit. His partner was left to run the house and the heater which she had no previous experience with. I began to get calls from her saying politely that she was having some smoke problems each time she lit the stove and put it in the down draft mode after initially firing it in the updraft mode.  My over the phone check list of solutions did not solve her problem, so I said that I would drive the four hours to their home at no charge but that I would also bring with me a licensed chimney sweep friend and that he would bill for his time.  Once we arrived, I inspected all of the doors and channels and found nothing open or obstructed and asked her to go through her firing drill for me.  As noted over the phone, she opened the by-pass damper as prescribed for start up and several minutes into the smoke free burn watched her shut the by pass damper and the unit immediately began to leak smoke into the room around the soot door and loading door apertures.  I asked her if she had opened the shut off damper to the chimney that regulates the draft for the unit especially when the heater was operating in the down draft mode.  She replied, “What shut off damper?”  I explained that her chimney and heater were separated by a couple feet and that there were horizontal brick transition flues at the top and bottom of the heater.  The top horizontal transition flue housed the bypass channel and the bottom horizontal transition flue housed a second damper to control the unit during down draft operation.  We had not mounted the lower damper in the chimney because the basement unit and the upstairs unit shared the same chimney flue and it’s important to always have the chimney flue open for either one or both heaters.  Both units had base exit dampers mounted in the horizontal transition sections leading to the chimney.  Upstairs, where our client was trying to light the stove, the family had pushed a firewood container in front of the horizontal transition section and in his hasty departure, our architect/builder/sailor had forgotten to tell his wife about the damper behind the wood storage.  We pulled the wood storage container out into the room a bit, opened the shut off damper and the smoke disappeared.  I smiled, her heater was now fixed. My friend Mike was paid for his time, and we drove four hours back to Maine.

A retired couple in New Hampshire with 40 years of wood burning experience had me build a brick masonry heater and chimney in their new home.  For the first month or so, everything worked perfectly and the couple developed a technique on their own of bumping up the upper chamber oven temperature one hundred degrees above “normal” by loosely laying three smaller split pieces of wood over the incoming smoke and flame throat at the center of the oven floor.  Burning gases coming through the throat would easily ignite the second tier of firewood and as those pieces burned directly in the oven they would add the increase in oven temperatures that the couple desired since they were doing lots of cooking and baking in it. One day, I got a concerned call from George saying that the heater was starting to smoke a bit.  I asked him to check all soot doors for tightness, passages for obstructions and dampers for function. He reported that he found no problems.  The next call was a bit more concerned and not able to solve the mystery.  By the third call, there was genuine anger/frustratichimney2on in his voice and I knew it was time to load up the truck and make a courtesy call to New Hampshire to see the problem.   When I arrived I checked all the soot doors for tightness, channels for obstruction and dampers for proper operation – no problems.   Everything on the main level of the house where the heater sat seemed in perfect working order.  We went into the basement and I opened the 8” by 8” clean out door there and asked for a small pocket mirror which I placed inside the chimney at an angle so that I could see it and the image up through the chimney looking for any obstruction that might be in the chimney.  I could see a clear white square up at the top of the chimney meaning no obstruction within the chimney.  The mystery remained unsolved, I next asked for an extension ladder, went outside and leaned it against the roof.  From the roof to the ridge required a second ladder and a hook or me working my way up the roof with hand holds along the roofs edge.  At the roof top, the walk along the ridge to the chimney was short and there atop the chimney I found a square of 1/4” hardware cloth fitted over the flue to keep out squirrels, bats, chimney swifts or maybe wood ducks.  The owners had decided, with no discussion with me, to add this fitted square of hardware cloth after my departure.  I noticed that the entire panel was completely occluded with a fine layer of fly ash nicely caught on the mesh.  I gingerly removed the mesh panel (being careful not to dislodge the fly ash film), and worked my way down to the ground.  I handed the mesh to George let him know his heater was now fixed and to please leave the chimney “open” thereafter. We always put a masonry rain cap at the top of the chimney about three courses above the termination of the flue.  Nothing the owners had done affected the rain cap in any way, but the mesh had slowly filled up with fly ash over a month or two of operation.  A hand shake and a smile later, I was wiser and no richer headed back to Maine. No more smoke calls occurred after the wire mesh was removed.

In China, Maine we built a beautiful “Corinthian” stone veneered see through heater with wrap around heated benches and a side exit chimney.  The heater worked perfectly for several years and then one day I got a call from the owners that it was starting to smoke.  More puzzling to them was the fact that they had just had the chimney and channels professionally cleaned by a Sweep.  I turned to my apprentice, we cleaned and put down our tools. I told him to come along with me as this would prove to be a good piece of education and that I could predict right then what the problem was going to be.  We drove the half hour to the job.  The family was dining at their table for supper.  I asked them to keep eating while I inspected the system.  Armed with a flashlight, we could see that the channels were all clear, the soot doors all tight and the dampers working properly.  Next we descended to the basement.  I recalled that the chimney was towards the outside wall in a space not as tall as the rest of the basement and therefore not inviting to inspect easily.  I had placed the clean out door for the chimney on the face of the chimney towards the house foundation wall.  When we reached the far side of the chimney where the clean out door was, I found (as I had suspected) a wide open door.  After his thorough cleaning, the Sweep had left the door open and without adequate draft within the chimney, through the heater rather than through the open clean out door, the heater was smoking.  I left the door open and called down the family. One by one they trooped down the stairs and came through the lower space to the far side of the chimney to witness the open door.  I gently shut the door and announced that the heater was now fixed and then we were on our way.  Another smokey mystery was solved.
I told Peter a story about a heater that an apprentice of mine, John Fisher, (a very gifted artist and craftsman) had built out of field stone with an owner builder in New Hampshire. John had prepared a lovely colored pencil proposal drawing of the heater before he began.  When finished it was beautiful and followed the proposal sketch closely.  To celebrate the completion of the heater, the owners decided to have a house and heater warming party to which I was invited.  I arrived with people draped all around the heater and seated on the heated bench with a fire burning merrily in the firebox.  I caught a whiff of smoke in the air which nobody else seemed to notice and decided to investigate a bit on my own so it wouldn’t ruin the mood of the party. I made my way down to the basement and where the clean out door to the chimney was supposed to be, there was nothing but a hole.  The owner had promised to mount a clean out door there but had forgotten to.  We gathered up some pink insulation to make a temporary plug for the hole. The smoke smell immediately disappeared of course and the clean out door was added shortly after. John Fisher went on to design and build many beautiful masonry heaters with me and others. He followed his heart and a young woman to Sweden where he learned to speak Swedish and became an antique tiled heater repairman and eventually established himself as a master oven designer and builder.
In New York, I built a top exit (five tube design: up the center for one, down the two front corners for two and three, and up the rear corners for four and five, and then together and out the top) custom made polished soapstone heater for a couple from Maryland who were going to move to their new home in New York on masonry-heaterfamily land. I negotiated the project by phone and email and built the heater to receive a UL listed metal chimney all without ever meeting the clients in person.  When the house was finished, the owners came to the home for a weekend, armed with my Owner Operating and Firing Instruction Manual and decided to light the heater which also featured an upper chamber oven that they intended to use frequently for pizza which they love.  The break in burn efforts proved unsuccessful however, and several attempts at lighting the stove produced smoke but no good draft each time.  I told them to be patient and that I would gladly stop by and find the problem on my next pass through New York on my way to New Jersey within a month.  There was no rush as heating season had not started and I finally got to meet my clients and their troublesome heater.  I spent several minutes on my hands and knees opening all the soot doors and peering into the channels with a flashlight to look for any problems and found none.  I checked the dampers, they were working properly or so it seemed.  With a top exit chimney there was no need to go to the basement to look into a chimney there, as there was none.  I laid a very small fire with kindling and paper and lit it, but I didn’t have any more luck than my clients had experienced, and we soon had smoke leaking out around the doors into the room.  Thinking, I puzzled over this for about fifteen minutes until I finally remembered to open the upper chamber bake oven door and there the mystery was immediately solved.  As a special gestOven-bricksure for my pizza loving clients, I had installed a pair of split firebricks on little cut in shelves in the oven throat so that they would have a solid oven floor and not need a special pizza stone during their pizza baking. Before each burn, the firebrick splits needed to be removed and set to the side of the smoke throat during the burn, and after the burn could be gently placed in their seats to create a solid heated floor.  There was no mention of these two firebrick oven floor splits in our operator manual because it is not something we normally do, so my clients had not tried to move them or seen them as the source of the problem.  Once we did move them, however, our smoke constipation problems were over and everything worked perfectly.  More smiles and handshakes and I was off to New Jersey.
I recalled the story of the heater that we built for an owner builder/artist and his wife in South Egremont, Massachusetts.  The house was slowly and carefully built around a gorgeous timber frame.  It took two more years after our departure for the home to be finished and only then did the owner try to light his heater.  When he did, it started to smoke, so he called and asked for help.  The Massachusetts border is six hours from home and when none of my normal solutions offered an answer, I decided to call in a friend, Steve Bushway, who lived not far from South Egremont and had a chimney scan camera as part of his chimney sweep business.  Steve climbed atop the chimney and lowered his little video camera and there at the position of the horizontally mounted guillotine damper, found a perfect thin layer of mortar indicating that we had somehow built the chimney and failed to take out the damper from its frame while we built the chimney.  I was working with a friend at the time and it is always fun to say that my friend left the damper in.  When we build chimneys we always take the damper out and mount the damper frame as part of the stacked and flexing flue tile system which rises and falls a bit with each burn and is not attached to the veneer masonry.  As we go up, we build two feet of masonry and leave a plywood plug on top of the last tile with a handle sticking out of the top of the plug. We scrape mortar off the plug and then gently lift it up with any remaining debris on it, brush off any remaining mortar debris and let down the next two foot section of flue tile with refractory mortar already troweled on to the bottom of the unit. Around each tile we cut two inch strips of quarter inch mineral wool, fold them double and tuck them in all around the newly placed flue tile to keep out excess mortar as well as to stabilize the flue. At the base of the chimney we put sand or some loose empty mortar bags to catch any falling mortar and not build a plug of mortar on the bottom of the chimney.  In this case, one of us had left the damper plate in and any falling mortar had landed on the damper plate and left a thin layer of mortar covering the damper.  Once the damper was removed for lighting the heater, the thin layer of dry mortar had remained and the heater would not draw.  Steve solved the problem once he found it, by dropping a brick or two through the system from the top of the chimney and everything then worked fine.  In older days, it is said that masons often left a piece of polished glass similarly locked in the chimney which would be invisible with the mirror test at the bottom of the chimney. Until the masonry work was paid for the fireplace would not draft at all, but once payment was complete, the mason could drop a brick through the chimney and everything would work perfectly.

My next door neighbors, Al and Patty Baldwin, recently talked with my son Scott about converting their thirty something year old masonry heater into a wood fired brick oven.  It was one of the very early masonry heaters that I had built and is documented in one of the self published newsprint Masonry Stove Guild Newsletters that we sent to people all over the States in the late ’70s to get the masonry heater ball rolling.  We built the Baldwin heater in a hands-on workshop format and it included a heater with no upper chamber oven (which was invented years later in Finland by Heikki Hyytiainen) as well as a large cookstove made up with metal parts from an antique lumber camp cookstove.  We built the foundation with a center partition and I recall working on one side while another IMG_3042person did the other side.  We came out of our respective holes when each side was finished     and laid down the form for pouring the concrete capping slab and got the slab reinforced and poured.  The next day I inquired where my second wooden step ladder was.  It turned out that the apprentice building the other section had left it in the hole and there it remains today.  Al punched through the wall a little getting ready for the oven conversion and said that it is still there in good condition.  Scott and Al worked out the basic design for the oven conversion but I was assigned to do the building, and Al did all the demo and prep work with a young friend.  He also wanted to change the cooker to a down draft exit versus the originally exposed top exit stove pipe exit.  As he was upside down inside the partially deconstructed cookstove trying to create a base exit flue under the original firebox of the heater, Al encountered something very soft and furry and quickly jerked his hand back. The object did not move so he reached in again gingerly and pulled it out.  It was a large bird that it had worked its way up into one of the heater channels.  He thought it might be a Pileated Woodpecker because of its size and distinctive crest.  The mummified bird was completely black on one side but the other side showed white and a mahogany brown and the crest looked to me like the crest of a Merganser. I went home with bird in hand and looked it up in my bird book and noted that the Merganser has a pointed bill and serrated teeth on the bill just as my handheld specimen had and of course webbed feet.  The one un-charred foot showed the remains of a distinctive webbing.  It was a Merganser for sure, dead and dried and at the bottom of a very tall chimney, the second duck trap heater chimney we had found.

We restored the cooker with a new base exit and changed the heater into a bake oven with a reduced size custom cut Le Panyol core with a fourteen inch cantilevered projection into the room built on a reinforced black concrete molded slab that Al designed and poured.  Everything drafts well and Al cooked his Paradise Heater-1Thanksgiving in the oven.  earnest_chebeague_1A friend on Chebeague Island in Casco Bay off of Portland, Maine, had me design and build a heater in a new passive solar home for him and his wife a few years ago.  It was a stuccoed brick see through heater with an upper chamber oven and a large heated bench and wood box and a metal chimney transition off to one side.  It has always worked well. After this jump into passive solar Green building design, Bob became quite committed to building more Green homes and eventually found another heater project for me just two lots away from his own home.  Ryan Neidhold and I built the heater last spring in a modest, well designed, very tight house for a recently retired couple who helped us out a bit with hands on work during some of the project.  We were very happy to find a red rock on a local beach that was almost a perfect map of the outline of the island so we set it as a little sculpture in the face of their chimney.  The house was not completed for some months after we left and late in the fall the owners decided to try some burns in the heater.  I was on the road at the time and began to get calls and emails from Bob indicating that there were some smoke issues with the heater.  There was a sophisticated air exchange system in the house, but no direct outside make-up air placed in the vicinity of the heater, so we wondered if that might be the issue.  Both Bob and the owners were certain that the heater was not at fault, but the mystery remained and the smoking problem got worse and quite serious.  Finally after a very concerned communication I got a message that the problem had been solved.  The combination of green wood and a spark arrestor on the chimney top, had, like the hardware cloth in New Hampshire, gotten completely clogged with soot and fly ash. (No wood stove should ever be burned with wet wood.)   With the spark arrestor removed and a swap of green wood for dry, the smoke problem disappeared.

Anyway, after Peter’s initial concerned call, I continued to work on the big heater project with Ryan and Peter Skove in Pittsfield, Massachusetts. After a few days of hearing my smokey heater stories, Peter Moore called again this time with a very buoyant, relieved tone in his voice.  I first asked him how he felt instead of asking him about the problem, he responded that he was elated. Armed with my many stories he had gone back again to his daughter’s heater with new courage, determination and a very powerful lamp.  When he got to the base of the chimney, he could see light at the top of the chimney but only through the small carbon monoxide slot in the damper which we heater builders all include.  The rest of the opening appeared to be occluded.  With some excitement, Peter climbed to the top of the chimney and shone the powerful light down and there, sure enough, was the tell tale layer of thin mortar that had formed over the damper which had been left in position by mistake while the heater was being built. Peter knew just what to do. He went down, removed the damper and then came back up the chimney with two bricks; voila! He was a confident heater builder and father once again.  The draft was restored and the smoke was gone.  Smoke, or “Mr. Smoke” as we like to call him, does not want to or like to get stuck.  He wants to get up and out.  He only comes into the living space when he is either sucked into the room or he can’t find a way out.  Give him a draft and a passage and he will find a way up and out.
The heater we just finished in Pittsfield is another top exit unit with a double down draft layout.  It was built inside an existing fireplace shell.  To create an exit to the chimneyDSCF0293, we went up the center and turned the bake oven ceiling around so that the second smoke throat at the top of the bake oven exited at the rear.  The smoke then comes down a total of four channels (two on each side) and then slides under horizontal baffles made of a double layer of kiln shelves and comes all the way forward into the lower front corners of the front mounted heated bench.  It then heads on each side toward the center of the bench, climbs up to a second layer around another set of baffles and then reenters the heater at the front corners, climbing up two channels on each side (making a total of nine channels not including the four bench channels), and reaches the top of the heater where the channels come together above the oven arch and are separated from the back channels by a by-pass damper and a cast refractory vertical baffle which we poured there.  The unit has a tall chimney and the house is perched on a little knoll.  With the by-pass channel damper open to establish the draft with no ducks in the way or open doors, the first fire and all those after, have worked like a charm; the fire and Mr. Smoke move easily into the down draft mode without any complaints, enchanting the room with firelight from both the firebox and oven, filling the house with warmth and beckoning the capable cooks within to bring the pans to the oven which will be ready, once the fire is down to small coals, ready to do its baking job.
Albie Barden

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