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rocket mass heaters

RMH for Dummies! Please help guide me through my first build!

pollinator

Posts: 231

Location: Western Washington State

posted 7 years ago

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Quick background:
I am a stay at home mom with 4 kids (w/ a b.s. in Microbiology). I have no building experience and struggle mentally with spatial relations.
We are in Western WA. I am building a heater for an unheated addition (my kids playroom). We have been here 9 years and have used space heaters. The room is like a cold sink for the entire house.
I am using the book by Ernie and Erica and am using their 6" annex heater plans, as opposed to having design my own.
My goal was to be done by Thanksgiving. Now I am hoping for x-mas.
I have accumulated free fire brick and clay brick. I have been de-mortering, but still have a ways to go. It seems I need to get some additional fire brick.
I have 55 gallon drum. I ordered the ducting new, based on the list of material in the plans.
I am dry running layout and builds now.
We live in an unincorporated area. After inquiring on codes etc. and getting no where, I am just going for it. Since this particular design was used for getting a code in Portland, I figured I should be okay.
PLEASE HELP!! It is going to be a "babysitting" project (I will need lots of help).
Spec. on the plans:

6" System
riser: 47", 5x 5.5
burn tunnel " 21"
fire box: 5 x 5.5

Today's questions

1) If you look at the layout of the room, and the way I have done the layout (photo 1), the point of chimney is right in front of the window. Can I move it to behind the barrel, if I pull it up forward? It then juts far in the middle of the room. Is there another way to make it work? Chimney placement is on a low (to no) pitch roof). Could I rotate the J unit 180 degrees, so the firebox is parallel with the bench?

2) I am going to do a fire brick riser, wrapped in rockwool insulation. With the current width of the riser bricks. the insulation cage is going to create a tight fit with the barrel. Is this okay?

Thank you!

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thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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Hi Staci; Welcome to permies! To answer your questions ,#1 , yes the core unit can face anyway convenient, biggest thing is to have a large enough transition area from your barrel to start of your horizontal pipe . #2 , 2" is acceptable clearance as long as the transition area is of good size. I see all your firebricks appear to be full size and heavy dense ones ? Do you have access to split firebrick ? insulating fire brick ?Masonry supply houses are the place to purchase these specialty bricks. In Spokane you can buy them from (White Block in Spokane valley) In a perfect world you would have insulating firebrick for the entire core and riser and only use the heavy bricks in the feed tube . Sadly few of us live in that world... To work with what you have , have you considered making a matt walker style fireclay/perlite riser ? Very cheap & easy to make .... can be lifted off of your core and set aside in the event of a rebuild . If you search my posts you will find many pictures of one. Here is a link to a permies post about transition areas as well, if it doesn't work simply look on the best this year column . https://permies.com/t/61657/Flue-exhaust-transition-plenum-pictures#525886 . Your floor where you are placing this is concrete? If so you will want a several inch thick layer of straw filled cob under your horizontal pipes and under your core a mix of fireclay/perlite is recommended to keep the heat coming up not going down. Isolation from your outside wall as well.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 7 years ago

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Hi Thomas,
Thank you for the feedback/reply!

Based on Erica and Ernies's guidebook and plans, it was my understanding that firebrick heat riser was the way to go. The original design was a perlite/fire clay riser, but it was burned out in a short time. The updated design suggested firebrick with insulation.
What is the issue with the firebrick? Does it absorb too much heat?

I will read up on the transition are at the base.

Flooring is brick, I plan to insulate above it, as well as along the walls (clay/perlite).

Thank you.
** I found some insulating firebrick in seattle. $87 for 24. If that is the way to go, could I just do that for the riser??

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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My first fireclay/perlite riser lasted 3 years and only failed when the outer grease barrel rusted where it sat on the core causing the inner riser to slightly crack (still worked perfect) I should mention that it was removed 2 times and put back during core changes / rebuilds... try that with a brick riser.... I still use my second riser .... they are a good cheap alternative. Someday ... I will spring for a ceramic riser. I believe that 1/2 or split firebrick wrapped with rock wool is the suggested way to make a more permanent riser. Insulated bricks or a ceramic fiber riser would be the (Cadillac of risers) . Yes, the issue with the dense bricks is they hold heat ... stealing it from your burn until they are thoroughly heated up. Using the split bricks takes half the time to preheat . Insulated bricks or ceramic fiber steal virtually none. Your 5 x 5.5 burn tunnel is 5" wide and 5.5" deep correct ? I have only built an 8" where everything is normally 7.5 x 7.5" I made my burn tunnel 8" deep x 7.5 wide to allow for a 1/2" buildup of fly ash.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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Yes, just saw your edit. $87 or 3.60 each is a very good price and would be a superb choice for your riser ... and part of your core if you had enough.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 7 years ago

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Hi Thomas,

Based on cost, I think my options would be:

1) move ahead w/ hard fire brick as is, and insulating blanket

2) do a clay/perlite riser (would this be 6" pipe to maintain the CSA for the 6" system?), with insulating firebrick tunnel.
**could I insulate the riser with my blanket too...would that do anything? Hate to waste my $$ blanket

(then switch to insulating firebrick at a later time.

3) do a insulating firebrick (with blanket?) riser with hard firebrick tunnel.

Which would you think?
Thanks!

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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I vote for option #2. As far as your blanket goes, I do not think it would do anything on a F.C. perlite riser... not sure what you paid for it but I would either resell it to a like minded"permies" person who needs one or just put it aside for your second build. In your photos I did not see any "black" stove pipe sections. I highly recommend one stick leaving your transition area, as its a very high heat spot. Then switch to thin wall HVAC pipe ,use one more piece of black pipe where you pop up out of your mass as it is a high abrasion spot. Back to hvac up to your PROPER stove pipe roof jack. That is the spot any "inspector " would red flag instantly, also some later renter could try to run a conventional wood burner with it... As far as your riser construction, you can use a piece of 6" ID cardboard concrete form "sonotube" it burns out with the first fire. Find your 16 gallon grease barrel at most any quick lube store for free or cheap. Mix your clay perlite as dry as you can, too wet can cause your inner form to sag prier to first burn. Also if its not raining to much do a mock build and burn outside , your kids will love it and it gives you some practice. Were you planning on a cob exterior for your bench ? Or perhaps red clay bricks? For me, before my first build the making of cob seemed to be the mysterious portion of building a rmh ... its not ... its just sandy mud, lots of sand compared to the amount of clay. No ocean sand, its to fine , river / creek sand or builders sand. Be sure to find a barrel with a removable lid, it makes things much easier.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 7 years ago

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Hi,
My heat riser needs to be 47"...is the oil barrel that tall? Could I use 6" duct pipe with 8" duct pipe outer and pack this with the perlite mix to the proper height? (I know pipes would burn out). The clay store has something called refractory cement...would this have a use here.
My barrel does have a removable lid. I should cut out the bottom and then leave the lid on top as removeable? It does have a metal spout. If I seal that, would it be okay?
I will plan on some test fires outside. family event

Stove pipe is also going to lead to the (Class A) chimney set up.
Right now, I have a rectangle to 6" cirlcle duct piece coming out from under the barrel. A T is connected to this , to be a clean out. These should be stove pipe here?

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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The height of your 55 gal barrel is easily adjusted with bricks and cob to get the correct spacing between the top of the riser and the bottom of the barrel. Yes on cutting out the bottom of your barrel and leaving your removable lid intact. Both the lid and the "spout should have no plastic gaskets, they will melt. you need a rope type wood stove gasket for the big lid and refractory cement on the little screw cap. No on a 6" pipe inside an 8" that's only 1" thick in between , not enough , 2-3" minimum thickness. The thin wall pipe could melt in the temps just after the core. For your transition area I suggest a clay brick box with a clean out door and an ash pit before your horizontal pipe leaves. This is how mine is , you can see good pictures of it in the transition post I linked too earlier, or in any of my older posts. Yes , you could use refractory cement if it is insulating. Good to hear you have a class A chimney set up!

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For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
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thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 7 years ago

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Just realized what you were asking. No a grease barrel isn't quite that tall . You make your inner form the height you need and taper down your clay mix to the barrel.

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For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
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Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Hi,
So after an 8 month break, I am back to it. ALL/ANY help is appreciated.
3 questions now: (I tried to attach pics)

1) I have salvaged fire brick. All are dense type. Some are grey and smooth, others are more grainy/coarse and yellowish. I bought splits for the heat riser ($4.05/ brick was the cheapest I could find.)
Is it okay to interchange these types of bricks in the RMH?

2) Building the mock up riser and burn tunnel is a challenge already. I have a huge deficit in spatial relations/orientations. Feeling defeated before I begin. I am going with a 6" system (in hindsight 8" might have been easier, but I already have the 6" stuff).
I am experimenting with 5"x6", 5.5" X 5.5", etc. dimensions, keeping CSA of 30. No matter what, I have a gap too narrow to put in another split or a full brick in the area between the feed and riser.

3) What determines the height of the burn tunnel?? My stats so far: 48" riser, 23" burn tunnel, 16" fuel feed

Thanks!!

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Eric Hammond

Posts: 400

Location: SW Missouri

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posted 6 years ago

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Staci Kopcha wrote:Hi,
So after an 8 month break, I am back to it. ALL/ANY help is appreciated.
3 questions now: (I tried to attach pics)

1) I have salvaged fire brick. All are dense type. Some are grey and smooth, others are more grainy/coarse and yellowish. I bought splits for the heat riser ($4.05/ brick was the cheapest I could find.)
Is it okay to interchange these types of bricks in the RMH?

2) Building the mock up riser and burn tunnel is a challenge already. I have a huge deficit in spatial relations/orientations. Feeling defeated before I begin. I am going with a 6" system (in hindsight 8" might have been easier, but I already have the 6" stuff).
I am experimenting with 5"x6", 5.5" X 5.5", etc. dimensions, keeping CSA of 30. No matter what, I have a gap too narrow to put in another split or a full brick in the area between the feed and riser.

3) What determines the height of the burn tunnel?? My stats so far: 48" riser, 23" burn tunnel, 16" fuel feed

Thanks!!

1) mixing and matching is fine, the only issue you might run in to is if the dimensions of the bricks are different from each other. I would segregate the bricks into piles by size with matching lengths widths and heights. Then try to complete each course with one size of brick. If they all measure the same this is irrelevant.

2)The book says in this course only, you may shift the back bricks of the heat riser forward to compensate for problems like your having. This will create a step in from the burn tunnel to the heat riser and from there up you will match the inside edges. I would try to use a thick bed of mortar between all of the bridge bricks in that course to take up some of the distance. It's hard to read the ruler but it looks like about 7/8ths. If you could use at least an 1/8 th inch mortar gap between all the bricks in that level you can bring the shift in at the back down to a half inch or less. Edit I went back and counted, it looks like you have 7 spaces in the burn tunnel that could be made to 1/8th mortar. It should end up pretty close.

3) the thickness of the bricks in row two and 3 determine the height of the burn tunnel, row two is layed normally and row three is placed on its side in your picture, flipping the orientation of row 3 would shorten the burn tunnel and flipping row 2 would raise it.

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Yesterday I put in the bottom foundation. I put in a 1.5 inch layer of clay stabilized perlite and then laid the bricks. I was careful to level. I dusted with sand and made effort to fill all of the cracks. This morning after settling, the sand appears to be running out the bottoms of my imperfect bricks- mainly those on the outside perimeter. I did not do a frame as Eric Hammond did so nicely, but retroactively framed to hold in the perlite.
QUESTIONs:
How do most people stabilize the perlite on the perimeter ?
Should I disassemble and start over?? And frame the outside?
There is sand now mixed in with the clay-perlite- is this a problem?
I have no grout- can I block the crevices with clay?

Thank you!!!

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thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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I would use a construction adhesive to stick those "perimeter bricks" down to the floor and to seal inside to each other. No worries about the sand mixing in , it won't hurt anything.
Seal with construction adhesive, (PL Premium) or you could use clay/mixed with sand to seal joints.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Glenn Herbert

Rocket Scientist

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Location: Upstate NY, zone 5

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posted 6 years ago

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Re the perlite running out and leaving gaps between your base bricks, once you have the surrounding bricks secured in place, you would want to fill level with perlite or perlite-clay anyway for best insulation. Just make sure to repack any empty crevices as you do that.

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Okay, Foundation, fuel feed, burn tunnel, heat riser all DONE. Measurements are consistent for 30 CSA (6"). Burn tunnel is 23", fuel feed 16", heat riser 48", 5.25x5.75 of fuel feed and heat riser AND all is level.

Onto....manifold?? Doing a brick manifold with a cleanout. In the "book" it says manifold should be 150X CSA where it is changing direction, and 2-4x where downward flowing.
Does this mean it is a cone shape with bottom bigger??
For 150 x CSA of 30, I calculated the diameter of the manifold to be 37.8 "... it that correct?
ANY help with brick manifold build would be appreciated. I plan to use red brick and clay slip and then cob over--sound okay?

THANK YOU!!

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thomas rubino

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Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Hi Staci; Here are some early pictures from my first build. You can see my brick transition area taking shape. Remember as you build your mass , rock holds more heat than cob... so if you use more rock ... you need to make less cob.
On your build, your going to want to think next about making a seat for your 55 gal barrel. The transition area is easy with a brick box. As you can see in the photos I molded an ash pit with cob at the very bottom and made sure my horizontal pipe was higher. A smooth finish of cob inside to promote gas flow, and A clean out door to empty the fly ash in the spring. Topped it off with a large flat rock ... feels great to rest on.

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For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Thank you, Thomas Rubino!
I have the chimney pipe set up to go sandwiched behind the barrel and the wall..can my cleanout still go back there?
I will use as much brick/stone as I can. Is the barrel support incorporated in the manifold?
I will do some mock up/playing around today and post some picks for feedback, if that is okay.
Thank you!

thomas rubino

rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Stacie; If you look back in this post you will see a picture from me called sizing it up. It clearly shows where the 55 gal barrel sits on top of the core. The "manifold" or transition area is behind the barrel , that is where your one of your clean outs should go. The other clean out should be at your 180 degree turn .

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Hi,
So I have laid out my pipes. I need to do some cuts to make it all fit. It will be about 20', which is small. I have been playing with manifold and getting very frustrated. I measured the height of where the bottom of the barrel needs to be for the 2" top clearance and marked it on the brick and with a cardboard bottom.
The chimney needs to go behind the barrel. (because of the window).

QUESTIONS:
- Does the barrel need support on all sides, or can 3/4 be supported with a quarter left "free hanging"?
-Is there clearance specifics between chimney and manifold. (I have 6" chimney clearance from wall with single wall stove pipe, but plan to add a heat shield, which I believe make is okay).
-LOOKING at my photos...any thoughts/recommendations??
-Cleanouts planned: under chimney, at 180, manifold, and just after transition from manifold to bench.
-Plans I am using have a rectangle to circle piece (okay for csa) for manifold air exit...any thoughts.

Thank you!

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thomas rubino

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posted 6 years ago

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#1) 3/4 of the barrel gets support , the rest hangs open to the manifold. #2) The chimney pipe where it pops up from your mass should be 130-150 F , not hot enough to do anything. The barrel will give off way more heat than the chimney. Finally in answer to your question, there is no specific clearance.
Your photos look good ,hard to see, but the transition area (manifold) you might want to make it a little larger. Bigger is better at that spot! No problem rectangle to round .
All around your looking Great , for a first build with no hands on help. Remember that cob comes apart easily and you add water and reuse it,(unlike concrete) !
If things are not just right on your first attempt its very easy to do a (on site) rebuild!

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Thank you, Thomas for all of your support and input! I feel so in over my head.
I hope to make some good progress this weekend.
Cob...another new thing to master!

thomas rubino

rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Hi Stacie; Cob... most people new to RMH fear making cob. Nothing is easier...work ...yes, but easy, kinda fun. Depending on the quality of your clay you may want as much as 3x sand to clay... yes that,s a lot. You can mix cob wet or you can mix it dry.
Personally as it was summer when I built my first rmh, I used dry clay. Throw down a large plastic tarp , bust dry clay into powder, add appropriate amount of sand, MIX , I just rolled the tarp around until I thought my mix was good then add water and do the same roll tarp stomp up and down on it add water as needed. If you are making insulated cob you would add straw at this time. After my cob was ready (sticky mud) I hauled the whole tarp indoors and went to work. I looked like a native, I turned dk tan, no shirt sweat running stomping in a little dance of cob making... all I needed was a feathered head dress! Great exercise.
Others choose to soak their clay in buckets of water creating a clay slip, then add sand do the cob dance and go to work.
One thing about your RMH , if you are enclosing your mass with brick as I did , then the consistency of the cob becomes much less important than if you are making an exposed cob bench.
You make cob ONE time , then you can reuse it forever! Wonderful stuff !!!
Good Luck Cobbing, have fun with it get some preteens involved .

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Thomas,
I have calculated the intended manifold area to be approx. 6, 216 square inches. Erica and Ernie's book says at least 150% of the CSA, so I am well over that.
For bricks, can I just use mortar I make with clay and sand?
For cob, I have dry fire clay and sand (free from someone). My first "play" attempt, yielded mortar-like substance. I collected some backyard dirt, it is VERY rocky, so it needs sifting first. I will try to add that in the mix next time.
NOW: off to cut some brick for the manifold.

Thanks.
Staci

thomas rubino

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posted 6 years ago

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Yes , fire clay and sand is a perfect mortar for sticking your bricks together. When mortaring brick you want only a thin layer, just enough to fill imperfections not the 1/4 " thick layer you would use with a concrete mortar.
If your manifold is larger than Ernie recommends than that will be fine. Was hard to see from the photos.
Is your mass going to be exposed Cob ? Or is it going to be encased ?
Fire clay for cob will certainly work, you would want 3 times as much sand in the mix.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

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Location: Western Washington State

posted 6 years ago

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Here is my work today. It doesn't look like much, but trying to get the bricks to fit in good order and size was a challenge. This is my dry run before mortar tomorrow.
I went with rectangle brick...but how to I cover and seal the top and side gaps?? Can I bridge bricks between the wall and lip of barrel?
Wondering if I should scrap and go round.

I planned to do exposed cob. My 4 year old wants it to be molded like a dragon. We'll be lucky if it is anything but ugly! :)

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thomas rubino

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posted 6 years ago

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Gaps can be bridged with rabbit wire & cob no need to change to round. Several inches thick minimum.
Exposed cob benches can be beautiful works of art. Your top two inches of cob on the bench will need a good mix .
I hope you have a good source of fire clay. Did you know home depot sells 100# sacks of builders sand for around ten bucks ?

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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CLEANOUTS- help!

I have 1/2 of my manifold mortared and set, 1/2 to go.
Planned cleanouts: 1) at the 180 turn
2) at a "T", placed just after the manifold to bench transition.
3) Barrel will have a removable lid
(chimney pipe is telescoping, so this could also be lifted up and then resealed).

QUESTION: Do you think the T- after the manifold id sufficient to clean the manifold (see pics). I can put my arm in and snake it a bit, but not so far. I am guessing we need to invest in a shop vac... would that work?
OR should I add another cleanout into the manifold directly?? IF I need to add another: Can I place it adjacent to the other tube? OR can it be in the TOP of the manifold??

Please help, as I want to get moving on the rest of my manifold ASAP, but need to know before if I need to add cleanout.
(I cross posted this).
Thank you!!!

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thomas rubino

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Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Stacie; I think the manifold needs its own access. Placing one on the top is not a good idea, too much chance for carbon monoxide leakage. The opposite side of the brick manifold would be perfect. That way when it is open you could look down your horizontal pipe. If you cant put one across, then adjacent will do. You need easy access to the manifold as it is your major ash collection point. The tee clean out you currently have past the manifold will not be very useful. The removable top on the barrel will mainly be to inspect your riser, not a lot of fly ash will collect there.
Shop vac's have a hard time with fly ash, it is so fine it eats up the motor. I do use one if I have to but I have found removing most by hand and then using a leaf blower to blow out any ash that has collected in the horizontal pipe works best for me.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

L Cho

Posts: 30

posted 6 years ago

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Staci,
I just came across this thread, and I noticed you have a vertical chimney. I hav only read part of the entire thread, but I wanted to point out that the design sketch you are working from has a horizontal exhaust, which in your case, would exit out under the window. The sketch shows a pipe pointing upwards like a chimney, but I am pretty sure that is a clean out port. Since a properly designed rocket mass heater has a very low exhaust temperature, a normal insulated chimney is not necessary. Exhaust temp should be like that of a clothes dryer.

Staci Kopcha

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Posts: 231

Location: Western Washington State

posted 6 years ago

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Thanks, Thomas.
I SO hate to undo my already mortared side BUT better in the long run.
Thanks for the quick reply.

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Worked hard today. Masonry is definitely not my forte. Should have known by the fact that I was never into Legos.
Still, I managed to get in the cleanout, and nearly finish the manifold (sides). I think the clean out should be flush against the bricks on the inside (?), so I may try to trim retroactively.
Cutting the ducting and fitting on the cap was another struggle.
Still, all in all, a productive day.

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thomas rubino

rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Stacie; That looks AWESOME ! Your doing a fine job! A new career for you in bricklaying!
I do agree trimming the inside is a good idea.
Keep up the good work.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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L Cho;
Although the original rmh by Ianto Evans used a horizontal exhaust it takes a special micro climate to have that work reliably year round. Most locations will have variable wind directions and will blow back thru your rmh, even a hot one that's running... scary scary that means smoke and sparks /flame inside ... A really bad deal.
Indeed the exhaust temp is 130-140 F similar to a cloths dryer . However any long exposed outdoor chimney pipe needs to be insulated . With a cold outdoor chimney the draft on a rmh will not want to flow... that translates to smoke back in your home... not good...

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Stacie; For the exposed clean out pipe inside. Use tin snips and make multiple short cuts towards the wall then simply fold the sheet metal tight to the wall. you could cob it over to keep smooth larimar flow.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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I woke up this morning and had a moment of panic. I forgot to put in the ducting to the bench. Ugh!! I paused to make dinner last night and was so eager to get back to it and finish, completely left it out.
SO, today I need to take apart the other side and re-do.

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Okay...today's pressing question ("please help!").

I am trying to put in ducting from manifold to bench. Plans called for a rectangle to circle piece (all within specs of CSA) (see first pic). For some reason, this looks like it would have some decreased air flow verses a direct circle. IF I do a direct circle, I have a moveable elbow to use, then comes a clean out and then the ducting .
Which seems like a good bet?

ALSO, is there anyway to connect two duct pipes without the pre-fab tapered end?

Off to domestic chores while I wait on this. My 8 year old is currently hand mixing clay slip!

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thomas rubino

rocket scientist

Posts: 6570

Location: latitude 47 N.W. montana zone 6A

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posted 6 years ago

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Stacie; Been busy today sorry for not responding sooner. The square to round adapter should be the same csa, but I think I would , just go with your round flex piece . Be sure to metal tape every joint especially the flex piece.
If it were me I would leave out your tee after the manifold, you won't need it anymore, after building the manifold access.
There is a crimping tool you can use to make stove pipe slip joints but it isn't free... somebody near you must have one (i do here in montana) but locating one closer could be hard. Possibly if there is a chimney sweep or a mason who builds block chimneys near you, they could have one.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Anthony Ryan

Posts: 1

posted 6 years ago

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Staci - Great post at an opportune time as we are just starting our 6" rocket stove working off the same drawing here down in New Zealand.
I was just about to order the fire bricks, yes was going to use full ones for the riser as well!
Following the response and threads;
1. I will look at a cast riser, or at least split bricks.
2. I had not thought much about the transition to the flue, this looks a key ash clearance area and the attached thread invaluable. good access ash pan and smooth chamber required.

Questions;

1. Are you going to introduce secondary air into riser tube? I have seen some information on this but no drawings, just comments on a sketch.
2. I intend to install water heating tubes around the main drum to run a wetback radiator system in the house. I have seen pics on this, are there any issues with cooling the drum that much? Does anyone have experience on this?

Cheers Anthony
Makahuri
Otaki
New Zealand

Staci Kopcha

pollinator

Posts: 231

Location: Western Washington State

posted 6 years ago

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Thanks, Thomas!! I scored a ton of free wood today, so have been loading/unloading that all day.
Have to make myself presentable and now go to School open houses, so manifold with ROUND port to bench will be tomorrow. Do I understant right that need to tape ALL the joints (so most of the pipe) of the flex- 90 section?

Thanks again!!

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