From OWB to EFM520 Installed in Truck Box

Congatulations!!!

You will LOVE this EFM! If you put your auger strait into that big bin your talking about building, the only tending you need to do is dump the ash pan every few days. Unless you come up the an ash auger system. This winter you will have so much more time on your hands you won't know what to do with yourself!

What model is it? 520, 700, 900?

RobR. is correct about the chimney draft, don't under estimate this. Yes, a coal stoker has a foced air blower but, you need to have enough chimney draft to evacuate that air from the fire box. If you don't, the fire box inside pressure will become positive. When that happens, hot gasses will try to get out any way they can, which will cause all kinds of problems AND you will use more coal than you need too.
The cheapest way I have found to overcome this is to find some used insulated stainless pipe. DO NOT get the tripple wall air channel type pipe, that has no insulation, great for keeping high temps off of flamable objects but BAD for keeping heat in the chimney to maintain a draft. You will need 8" ID or bigger, there is a lot of used 6" ID out there for sale, don't be tempted, it isn't big enough for your EFM.

You also can't use a short chimney like on your OWB. Your EFM does such a good job of scrubbing the heat from the outlet gasses that at full burn your chimney temps will be under 300 degrees. Heating DHW in the summer they will be well under 200 degrees. So, you need to keep as much heat in the chimney as possible and you will need a high chimney, I would guess at a minimum 10 feet.

Keep us up dated on the install. Heck, I might even stop up there to see it if I'm in the area, looks nice!

-Don

Ditto on the above post. Read it a couple of times.

The manual calls for 8x8 masonry w/tile liner, min 15' height, or 9" dia. Metalbestos, etc. min 15' height, sufficient to produce at least -0.05 draft. Old-school specs recommended 8"x8"x30'.

Mike

So a masonry chimney will build up temp wise & hold that heat till the next firing ? We have been looking at an 8" ductile iron pipe with a thin cement liner,i think they would be used for water mains ? If we go masonry chimney,maybe set it on the floor in the box ,up thru the roof ,that would eliminate the chimney thimble & box at odds with each other as the box shifts from freezing & thawing ground below. Thanks to all who have sent advice on here & with pm's,keeps the thinker going for possible better/easier/cheaper ways. Rob,i was planning on drywall on the walls & ceiling,you have me thinking about a cheaper way. Sometime back in a thread that I can't recall,i stated that we had been getting free wood from a local truck box builder & that from time to time we were also able to get some usable lumber & plywood for projects. I got raked across the coals from a certain member who did not take the time to read thoroughly because " there is no such thing as free wood" & "your neighbors probably love you for the smoke from burning plywood ".Well,free lumber to our $$ rescue, we have some plywood pieces & boards that can be used on the walls,thanks for the brain nudge.I am enjoying all the answers & opinions so far,the chimney idea might raise our project $$ higher but we can conserve a few $$ on some other things.

The 15-30' high chimney is measured from where ? Footer to top ,or thimble to top ? Does the clay liner actually hold the heat for hours ? If we install a pipe 25-30 feet high,will it not be sufficient height to draft properly ? Must there be heat in a tall chimney in order to have the correct draft ? When laying chimney block ,is there a required gap between the block & wood? as in a wooden wall ?

windyhill4.2 wrote:The 15-30' high chimney is measured from where ? Footer to top ,or thimble to top ? Does the clay liner actually hold the heat for hours ? If we install a pipe 25-30 feet high,will it not be sufficient height to draft properly ? Must there be heat in a tall chimney in order to have the correct draft ?

I would measure the chimney hight from where ever the flue outlet of the boiler is, since that is where the heat comes from.

If you build a masonary chimney, a round clay liner insulated from the outter masonary with vermiculite (I may have spelled that wrong) will work best, I think. Vermiculite is also used in gardening, same stuff.

A chimney works because there is a difference in pressure between the inside of the chimney and the outside atomsphere. This difference in pressure is caused by the difference in temperature between the gasses in the chimney and the outside air temperature. Hot gasses flow faster than cool gasses, relative to outside air temps. That's why when outside temps go up, it's more difficult for the chimney to maintain draft. There are other factors that will effect how the chimney drafts such as, wind and atmoshperic pressure changes.

The hight of the chimney helps keep the momentum of the gasses going. A short chimney cannot keep the momentum as long as a tall chimney.

Basically, you want a chimney the can pull more draft that you need and you regulate it with a boro dampener.

By the way, you will also need to plumb in some make-up air so the combustion blower has something to breath.

I am not a chimney expert but, since I installed my stoker boiler last January, I have learned that what I did was wrong. It all still works but, It will work better once I put up my new chimney. I'm just trying to make sure you don't make the same mistakes I did.

I hope this helps,

-Don

What ever you decide to do with the chimney your going to like the boiler. It was the best thing I've ever done. I was burning 3 to 4 triaxles of logs every year. Now I burn 9 tones of rice. I did replace the 45 foot masonary chimney through the center of my house though.

I like the masonry chimney idea,but the $$ required & the fact that the box might just move up & down a bit as the ground freezes & thaws & the chimney would stay put,resulting in thimble stress or an elongated hole,i think we will go with double wall insulated stainless chimney with a rain cap on top.Is the Ventis brand a good quality brand ? This would be roughly 1/2 price of a masonry chimney & I think I can install it my self,i do not do well with working high off the ground. cArNaGe , sounds like we both were burning the same amount of wood,if I can burn less than 15 tons I will be ,although I am not quite anxious enough for cold weather I certainly have some interesting things to look forward to this coming heating season. ONLY 9 TONS

Go through the top of the box. You will save hundreds and draft will be stronger for equal height.

franco b wrote:Go through the top of the box. You will save hundreds and draft will be stronger for equal height.

Are you saying that by going strait up I can delete one length of the vertical pipe ? (the one from the thimble to about the roof line) That would save some $$ but then I would have a potential roof leak .( flat roof on the box) & would allow any rain water that found its way into the chimney to leak down into boiler room & maybe into boiler ? Out thru the wall has less leak potential + Any rain that does make its way into the chimney would come down into the clean out tee at the bottom of the chimney & would still be outside.

You've Done It,Windy!

HB, we are DONE with wood & the WORK that goes with it. We are now done with site prep,done with making the trailer a box on the ground (that was a big step),i'll be glad when this project is completely done & the EFM is making the water hot & standing by ready to heat the buildings as needed.

windyhill4.2 wrote:

franco b wrote:Go through the top of the box. You will save hundreds and draft will be stronger for equal height.

Are you saying that by going strait up I can delete one length of the vertical pipe ? (the one from the thimble to about the roof line) That would save some $$ but then I would have a potential roof leak .( flat roof on the box) & would allow any rain water that found its way into the chimney to leak down into boiler room & maybe into boiler ? Out thru the wall has less leak potential + Any rain that does make its way into the chimney would come down into the clean out tee at the bottom of the chimney & would still be outside.

You can save a lot more than one length. You save a very expensive tee, the through the wall one foot piece, and maybe two lengths. You wont need the outside support but will need a roof support. Just as easy to cut a hole in roof as side wall. Flashing piece for flat roof that can be nailed or screwed down bedded in roofing cement if need be. Will also need brace for chimney above roof. Four feet of cheap galvanized pipe inside and one four foot section and one 3 foot section and one one foot section for 8 feet outside. 12 feet total chimney which I would try before adding more, which is easily done. the reason for the one foot section is that it is at the point where corrosion is most likely and cheaper to replace than a longer piece. Straight up and out will draft stronger than through the side wall which needs two right angle bends for the flue gas. Servicing the chimney is also easier with one 6 foot step ladder on the roof with no leaning out into space.

Excellent point. I forget the rule, but each 90 degree bend effectively "shortens" the chimney by a certain amount.

The trick will be a leak free transition through the flat roof. If sealant is required, I recommend a product called "Through the Roof". It works better than anything else I have ever tried.

Just make a "pitch pocket". Form a square out of 2x4's and fill it with roofing tar. That's how they do it on flat roofs.