Secondary Air Distribution System

Oh ok I understand now..

I wanted to do an update on my secondary air system. Today, I had the "salt and pepper" caps on my secondary air inlets. These caps only let a tiny amount of air in over the coal bed. Currently, I'm running a medium heat output fire, it's mature meaning about 10-11 hours into the burn cycle. My over the load door temp holding steady at 289 degrees and pipe at 198.

I decided to see what response I would get if I completely sealed the secondary air inlets. In a matter of 15 minutes, over the load door maintained 289 but pipe has fallen 10 degrees to 189 and is holding steady there.

I still see blue flames on top the coal bed.

My conclusion to this experiment is that a mature coal fire doesn't make any profitable advantage with secondary air. It seems that enough oxygen is still getting thru the coal bed to burn CO at the top. It's during the bake out of volatile gases after loading where I see the advantage of secondary air.

I realize that these characteristics may be different for different appliances under different conditions.

Would there be any advantage to using a heavier pipe, instead of the conduit, for the air tubes? Like either black or galvanized gas line? Heat transfer wise(which could be worse this way) and to last longer being the reasons.

Im thinking of trying something similar on an old stove I have but don't want to have to replace it in a few years. It would be for multi-fuel, hard/soft coal and some wood. It would lay on top of the firebrick and wrap around the stove with one air inlet.

Lightning, thank you very much for all the informations you took time to share on the forum.
Many say things but not many take time to verify what they say.
Have a Merry Christmas.

Warminmn - the lite weight electrical conduit has help up great so far. As far as preheating the secondary air, it's hard saying if a different material would make a noticeable difference. My pipes don't get much abuse thru using anthracite since the volatile gases are quite limited. If using bit or wood, I would definitely use something more substantial. I think the black iron pipe would be a great candidate. A secondary air distribution system for fuels with higher volatile gas levels I feel would have a huge impact on combustion performance. I may just do some testing with bit and wood to see, just not sure when lol..

Nortcan - thank you for the kind words sir and thank you for sharing your beautiful stoves. I always look forward to seeing your pictures and reading your posts.

Merry Christmas to all..

Thanks! I'll give the black iron a shot then. I want to keep my options open with this stove as to what I burn as it may end out being in an outbuilding at some point. And yes, great post! Ive read it thru a couple times in the last month.

I have black iron pipe in mine, routed in a way that pre heats it, without drilling holes in my stove.

Hotblast 1357 Mods

I want to chime in the "thanking Lightning" department. His experience, research and videos are the major reason I have stepped up my game in coal heating. Berlin is the "Wizard of bit" for sure but the testing/trial and error of Lightning (the mad scientist of Clayton type stoves) has been motivational for me. Thanks Lighting!

Thank you for the mention my friend. I take solace in knowing what I've learned and done can help others. As many with their own trials and tribulations have shared as well, to help others.. Thank you and Merry Christmas..

hotblast1357 wrote:I have black iron pipe in mine, routed in a way that pre heats it, without drilling holes in my stove.

Hotblast 1357 Mods

Thanks as I missed this post somehow.

We'll see what I come up with for preheating the pipe before it goes in as Im not 100% sure yet. Its a somewhat octogon shaped stove so it may be hard to go completely around it. Ive got the stove apart so it gives me options. Im not much on figuring out coal and temp usage data except useage for the whole season, just want to make it more useable.

Just a note regarding heat transfer in tubing/piping - if you look at commercial units that heat using tubes, inside the tubes they use what are call turbulators. Now of course these typically are designed to increase the transfer of heat from the hot gas running inside the tubes to the outside of the tubes, while in your application you are transferring heat in the opposite direction. However the basic principal should still apply. The turbulators cause the gas flowing inside the tubes to have greater physical contact with the tube walls, increasing the thermal transfer between the gas and the tube walls.

fwiw

dj

Lightning,
I forgot to say that: thank you for the Honest feed back you gave us about the modifications you made on your stove.
Too many times we read super restoration jobs, stove modifications...but never see the REAL results or a fire in the stove.

OK, so I installed 2 black pipes, one on each side on top of the firebrick. This way I can remove them easily compared to one pipe wrapping around the stove. I used 3/4" since Im using 2 of them. I did use regular galvanized on the flanges and washers as they are on the outside of the stove, but did burn the galvanize off them on some burning coal. The rest is black pipe. This is going to be a slicing grate, not a rocker/shaker, in case you notice the flat grate. And the threaded rod is just there to hold a couple fire bricks for a heat baffle.

After coming out of the stove I used a few large washers and a floor flange. Then a plate, spring, and bolt. I would like to get a couple dog ear/teardrop looking things for the covers, but for now a steel plate will work. I had to drill another hole in the plate so it will open all the way, and Im wondering if a normal spring will hold up to the heat but time will tell that.

Im not sure if I will have to drill a hole in the plate to keep a little air going thru the pipe or not. There is a little leakage around the plate.

I thought with Clayton/Hotblasts it was good to block the secondary air by putting insulation between the liners thus more air through coal bed. Why then are you adding secondary air back in via the tubes? Forgive me, im confused...

Stoker6268 wrote:I thought with Clayton/Hotblasts it was good to block the secondary air by putting insulation between the liners thus more air through coal bed. Why then are you adding secondary air back in via the tubes? Forgive me, im confused...

The first instance is bleeding off primary air. By adding the pipe the secondary air is independently controlled and added at a better place.