Exhaust in brick

[Exhaust Many Channels]

I'm considering venting my (1st) Rocket Mass Heater into a "chamber" which will then empty into individual brick channels which will then empty into a final chamber & from there into an 8" pipe to go outside.

I'm considering doing this so that I don't have the elbows in my "heat battery"

I'm open to anyone giving me the pros / cons to such an approach.

BTW, the floor of my new addition to my house ( affectionately called The Rocket Room ) is sand, sand and more sand ( and a fair percentage of clay-ish soil ).

I plan on digging down into the soil and building the base of the rocket so that the top of the base ( feed tube & fire tube are at ground level ). My exhaust will similarly be "buried" and become part of the floor, such that when you walk into the room, you'll see nothing but sand and perhaps a little bit of the top of the brickwork of the exhaust channels.

I'm thinking on laying down 2" aluminum foil sided styrofoam insulation under the exhaust channels so that I'm heating the ground below the channels as little as possible, tho not sure the insulation "is up to the task".

I know, a picture is worth a thousand words but I ain't got no pictures ... yet.

I know just enough to know I've got a lot more to learn ... so "larn me good" ;D

[larsmith]

You can tell that the above message was one of my first, posting as I typed in a description of topic where I should have been typing in my user ID. Sorry about that.

I'm surprised to have had so many reading the thread but again surprised I've not had the privilege of responses. Are there any out there who have any thoughts about this ?

[chronictom]

I think you have to keep in mind that everyone is doing other things as well and don't have time to respond as quickly as some of us would like...

I probably check back here about 100 times between peoples posts. lol

As for your idea itself, I can't tell you anything, I'm new to all this myself... but I will say that it does give me the impression of causing a lot more headaches to figure out and set up then using a run of pipe (or channel) through a bench.

That could be from a lack of understanding just what you mean though. I suggest you go get google sketch up and draw a rough idea of what you mean in it and then post a link for us. That way we all are starting at the same point in understanding what you mean.

Sketchup is free from here;

sketchup.google.com/

[larsmith]

My plan is to build a multi-channel exhaust "bed" and bury it in the sand floor of the room, as opposed to having a cob bed / bench above ground. I figured if I make a flat & (potentially) wide bed of exhaust channels, running horizontal to the ground, I could provide adequate flow as well as heat battery with reduced back pressure due to pipe elbows which are common to cob bench applications. I expect that a brick exhaust channel "bed" would reduce the chances of CO leaking ( as it is reported to do thru porous cob ). I've got the time. I've got the brick & mortar. I'm just wondering if I'm over-looking some (important) principles which I perhaps should be more thoroughly examining / considering.

[chronictom]

"I expect that a brick exhaust channel "bed" would reduce the chances of CO leaking ( as it is reported to do thru porous cob )."

I wouldn't swear to it, but I think you will find that issue was more of theorized it was possible to happen, not anyone reporting it had already happened.

As for the rest, it will have to wait til someone who has experience to answer in terms of the end effect of it.

Right off the bat, I think I can see you running into a problem that you will suck all the heat out of the exhaust and end up with nothing left to drive the draft up the chimney?

[chronictom]

Actually, on saying that... perhaps if you had the chimney base close to the stove itself, it could pick up enough heat from it (if you had solid thermal mass between them) to drive it?

As in, from the stove, it runs to your heat battery (floor, and drifts through there), the heat from the stove transmits across the thermal mass heating up the base of the chimney, starting the draft....

Just pure conjecture though... lol

[chronictom]

Sorry about yet another post in a row... my mind responds to the written word even if they are my own words... lol

This could apply to both your system and a bench system...

If you had a bypass damper system... so when you light the stove, it runs straight to the chimney, once it gets hot and is burning well, flip the damper over so it blocks the path from the stove to the chimney and opens up the pathways for the floor/bench??

[larsmith]

I'm considering a horizontal exhaust exit, directly out the side of the heat exchanger and directly into a box-shaped area I've simply called a "chamber". From that chamber, two or more exhaust channels, completely encased in firebrick or red brick, will continue away from the rocket heater. Instead of having one exhaust pipe, weaving back and forth thru a cob bench, totalling between 20 and 30 feet before exiting the building, I hope to have two or more individual channels, running side by side towards a final chamber to which a final exhaust pipe will be connected and exit the room.

What this would mean is that I would have, under sand, a number of exhaust channels adequate to equal the flow of one 8" exhaust pipe. I've even thought of having say four channels, two on top of two, forming an almost cube shaped exhaust which heads towards the exit wall. I'm make up in a relatively short linear distance the equivalent air space for exhaust to 1) heat the "heat battery" as well 2) reducing back press and 3) most ( any ? ) concerns about CO infiltration into house.

It "may" create some clean-out issues which I believe can be overcome by careful design.

[chronictom]

okay, the only thing I can say to that would be that having the channels on top of one another wouldn't be the way to go, I don't think. Having them spread out so each one is heating it's on section of floor may be better. Otherwise, the bottom channels will be bleeding heat into the upper ones.

[Donkey]

Hey.
Sorry it's taken so long for me to respond.. Been quite busy lately and missed a few posts.

I see no real trouble(s) with your plan in theory. I know someone who made a similar setup using square steel pipe and he is overjoyed with it..

The multiple channels should have conveniently located clean outs for each channel. You want to be able to reach all the dark, hidden parts.. Remember, when you double the size of any channel you quadruple its area. So working backwards - four, four inch sections of pipe (channels, etc.) would be used to split one eight incher.

Rigid insulation is not really meant to handle much heat and may off-gas, melt or catch fire close to the hottest side of things. Look around for alternatives, pumice comes to mind.

Roman hypocausts, which were made of clay tile, had a history of breaking, releasing CO into homes and killing folks.. Be aware that brick of just about any type can do the same. Perhaps you should think about using some other material for the top.. Steel plate or something..

[larsmith]

re: Bricks Breaking & CO issue ... We've purchased a new digital-LED CO detector expressly for that room and we have two other CO detectors through out the family ( a recommendation we make to all who're using CO-emitting equipment ).

TY for the notice re: bricks breaking in the hypocausts !! ... tho I didn't understand that CO concerns are nearly common with rocket heaters. How real are the possibilities ?

I've built a well-insulated 8'X8' room, in which I'm putting my rocket. I've purchased Benjamin-Moore fire-proofing paint and have ( so far ) used 2 gallons of that paint in the room and adjoining room ... and used a propane torch to test whether the paint actually works. I've you've not considered it yet, perhaps you should do your own research about using a intumescent ( fire-proofing) paint.

Is the possibility ( probability ? ) of breakage in a brick exhaust bed & leaking of CO any more real / tangible than with COB or other exhaust / chimneys in use with Rockets ? Or is it any more likely than breakage in "regular" russian / siberian masonry heater's brick exhaust structure ?

[chronictom]

well, this is an easy thing to avoid, although it gets back into using purchased products... we will be using actual stove pipe sealed with metal tape at the joints as out channel, which will then be encased in cob. The cob may crack, but there will be no leaks.

As for the CO detector, that is always good advice... for the cost of one, it would be silly to not get one at your earliest chance... (so says the guy who has been too cheap to buy one yet)...