Lots of smoke out the chimney ...and other problems.

I have an 8 inch system with a 29 inch riser, a burn chamber of 14 inches, and only about 20 feet horizontal capture. My exhaust is an "H" cowl atop about 4 feet of vertical stack. My RMH is dry. I have used only firebrick, cob, and granite around my ducting for the bench along with vermiculite insulation underneath. I burn only small pieces of well seasoned maple and oak. I also spent months making sure that all my internal measurements are the "ideal" proportions described in Ianto's book.

My Problems:

Even with the burn chamber just 2 inches below my barrel top, water boils VERY slowly. It takes hours.

With only 4 inches of cob and granite atop my ducting on the bench, the bench only gets warm within a foot of the barrel, and never really gets hot. I thought with only 4 inches I would be in danger of burning pillows and so forth. Nope.

The exhaust after only 20 feet of run is cool leaving the house, and produces thick dark wood smoke, the kind you would expect from a traditional wood stove.

Blow back. Even with the "H" cowl and placement on the lee side of our house, we are only able to run our RMH on the stillest of days.

?

Am I correct in assuming that the gasses are not mixing properly in order to re-burn?

Will shortening the burn chamber remedy my issues?

Are there any other solutions?

I live off grid, 5 miles from the nearest road or neighbor in northern Canada. If I don't get this fixed soon, it's gonna be a baaaad winter!









Thank you fire gurus for all your help.

You need a chimney. that pipe going out of the wall with the H cowl is worth fcuk all!

Put two 10' lenghts of pipe on top, to raise it above the apex, and insulate it. Then you'll see what it's worth. Your transition area might be a smidge small too.

Also, what is your top gap? Side gap? Heat riser and burn tunel insulation.

Satamax Antone wrote:You need a chimney. that pipe going out of the wall with the H cowl is worth fcuk all!

Put two 10' lenghts of pipe on top, to raise it above the apex, and insulate it. Then you'll see what it's worth. Your transition area might be a smidge small too.

Also, what is your top gap? Side gap? Heat riser and burn tunel insulation.

Thanks for your input. The top gap is 2 inches, Sides are 1.5 inches. Heat riser is insulated 9 inches on all sides with vermiculite/clay. Burn chamber is insulated 4-5 inches on all sides with vermiculite/clay. I belled out the transition area as described in Ianto's book.

I will try your suggestion, and am certainly not dismissing it. However, I was under the impression that since the exit temperature was already quite low (barely warm to touch), that my problem was further upstream rather than at the exit.

Can you take the top off the barrel to see how strong the basic feed tube, burn tunnel & riser are drafting?

You say 1.5" space around the sides of the heat riser & barrel, and "9 inches" of insulation. Are you saying the insulation is 9" thick around the riser? That seems like overkill, and if you only have 1.5" of space, you might be too tight for good flow there. Also, with only 1.5" of spae at the point where the manifold meets the horizontal duct, you would need a very wide duct to allow the gases to make the sharp turn. This is another potential major bottleneck.

Glenn Herbert wrote:Can you take the top off the barrel to see how strong the basic feed tube, burn tunnel & riser are drafting?

You say 1.5" space around the sides of the heat riser & barrel, and "9 inches" of insulation. Are you saying the insulation is 9" thick around the riser? That seems like overkill, and if you only have 1.5" of space, you might be too tight for good flow there. Also, with only 1.5" of spae at the point where the manifold meets the horizontal duct, you would need a very wide duct to allow the gases to make the sharp turn. This is another potential major bottleneck.

Thanks Glen,

I cannot take the top of the barrel off. However, in my mock-up, the j-tube proportions were very rockety. The space at the manifold is significantly wider than 1.5 inches, closer to 3-4. The barrel is also slightly offset creating a larger gap towards the manifold.

Carl Mathews : MAX is right! You will need a much taller final vertical chimney to clear all obstacles, minimum distance is 4' above the peak of the roof !

This will give you a much greater draw, and will greatly enhance your burn! If possible an effort should be made to ether box in or insulate the exterior
stove pipe. perhaps by a second stove pipe of larger diameter and seal the bottom and pour in penlight or stuff in fiberglass or rock wool insulation and
seal at the top very carefully ! Wet insulation is no insulation ! and frozen insulation will kill any draft you have !

This should take care of your exterior chimney and its draft, greatly strengthening your RMH and its performance !You should plan on joining your pipe
sections with at least two sheet metal screws, and adding bracing back to your roof or use guy wires !

Iwish i could say that this will solve all your problems, However -

With that conifer tree as close as it is to the side of the house you may need to go higher yet to deal with its closeness affecting your chimney when the
wind is From the wrong direction, even then this may only be a problem on starting a new fire in a cold RMH !

I hope this is timely and helps, for the good of the Craft ! Big AL