https://www.usstove.com/product/6-pack-pumice-fire-brick/
This is what is offered to buy as "single" fire bricks - priced per brick.
They are pumice so insulate better but actually...
THESE ARE CINDER BLOCKS & THEY MELT!!
Says one Amazon review.
So that's what they look like - melted and destroyed...
concrete
bricks will explode if they get wet and heat up before they dry out.
The heat will push the water out faster than the brick can take, Then
boom you got fire everywhere and hot brick too...
So that's probably what's causing the breakage... kind of interesting.
This fire brick is very porous.
So they are a "ceramic-sand" mix.
These don't hold up for the temperature I need...
The bricks feel very light and actually melted when they were around a hot fire
Several of the bricks cracked during the first fire after installation. Would not buy again.
...I made with over $300 of US Stove Firebrick. First step was a small
fire around 275 degrees for a few hours. The next morning I saw that 4
bricks had cracks in them!
the weight and composition is basically the same as a typical concrete paver so in a way I feel kind of ripped off.
This doesn't appear to be firebrick at all. This is more like cinderblock- very porous and light weight.
All these bricks broke after I fired my woodstove.
one cracked a bit and I never got the grill over 210 degrees.
These are lightweight bricks. (I believe the white specks are perlite) They are meant more for insulating from heat.
OK so those are 2.7 pounds each. How much does the brick I got weigh each?
So those first fire bricks definitely are not durable at high temperature. So the kind I got is Meeco but they are discontinued apparently - actually it is the same fire brick that Rutland sells.
Approximately: 21.5 pounds for six.
3.58 pounds! Wow definitely heavier!!
OK I think those are the same as the Rutland...
Rutland says 24 pounds for six. But the weight on the Meeco was not provided by Meeco - rather it was provided by the retailer. So probably just an approximation for sure!
Rutland duty fire bricks tested at 2500F for several hours and worked fine without cracking.
So much stronger!!
Not crumbling/cracking in the slightest
None of the ones I installed two years ago have broken.
The over all performance of the stove has nearly doubled.
Going
on our third season with this wood stove, the porous concrete-like
firebricks that were originally supplied with the unit were already in
need of replacement, with one brick broken, another deeply cracked.
After ordering one box and determining the Rutland bricks appeared to be
much better quality, opted to replace ALL 13 firebricks.
After just a couple successive fires, we've noticed these bricks insulate much better than the old ones,
So because they don't crack then they actually insulate better than the more porous "bricks."
I'll weigh them to see if they actually are the same as the Rutland bricks
NOPE - the MEECO are also crumbly!! I opened the box and took them out. They must be bigger than the US Stove bricks but they're the same material. Porous crumbly sandy.
Hmm they have the exact SAME dimensions as the Rutland brick.
That's the Meeco fire brick.
What's the Rutland?
says they have "crystalline silica" but no SDS. So they ARE different.
I bet this is the same brick - so Rutland orders them from this company I bet.
OK I'm ordering the Rutland bricks aka BNZ (wholesale). I can't buy them from BNZ since they're only a wholesaler.
OK I ordered it for pickup in a few days - I'm NOT gonna use crumbly firebricks that crack at low temperature after becoming too brittle. No - because with the ceramic fiber board the stove should be too hot! The Double M Innovations ceramic fiber board mod was based on SWITCHING to the better more dense stronger fire brick - so I gotta follow his plan.
Century Heat FW3000SD question" OK that thread on shows your steel
baffle!! It is the old model and has a hollow center - so it's a
"double" steel baffle!! Very wild. THAT clarifies everything. thanks "Mine has a hollow steel baffle that is part of the secondary air system. The back part of the baffle is made of firebrick." - from another thread called, "Century heat FW3000" (2017) - I knew I wasn't just making up what I was seeing. haha. It's a DOUBLE baffle!!
The label on the back of the stove says it's an S244 (CB00001 model), 2015. I'm pretty sure I bought it in the fall of 2016 from Menards, and it was around $350-$400.
@Double M Innovations A retail store has that model for $800 now but otherwise it's discontinued. haha. Definitely listed as secondary air stainless steel baffle. So you got really lucky with that design for those 1400 F. temps!! Otherwise that exhaust would not have cooled off so much by the time it leaves the collar. Pretty wild.
@Double M Innovations So here's my plan. I ordered from 3 separate businesses the stainless steel pipe and a coupler and a 90 degree elbow - all 1/2 inch 304. So I got that all together - as my secondary air going to the back up the wall behind the baffle - preheated along the bottom of the stove. I just ordered the BNZ (Rutland branded) dense strong firebrick like you have. So that will hold up the S-valve (as the batch box people call the secondary air tube). So then I have the 1 inch ceramic fiber board. I will then have the secondary air go up in between two baffles of ceramic fiber board. The top baffle will go up against the back stove wall. The bottom baffle will leave the space for the smoke to rise up to go into the secondary air and then in between the baffles to the front.
I already have a steel baffle with some space behind it. So I put one baffle on top and then some side wall fiber board to hold up a second baffle - and more fiber board on the back wall.
Then the six firebricks - four on the floor of the 18 inch long x 11 " stove and two on each side walls. Or maybe the two should go in the back. Actually I also got those cheap crumbly insulating pumice bricks. So I could put those in the side walls along the base.
So my stove is only for a 10 x 12 hut with my stuff too close to the stove - so I don't want any 1400 F. temps. haha. Also I don't have a ceramic door. I got a infrared gun rated to just over 1000 F.
So I also got the aluminum heat exchanger strips - six of them - and an Ecofan. I also got a stainless steel 4 foot duct pipe but I'll put it in later in the spring - along with a stainless steel elbow. I got duct clamps with the worm gear - four of them - I'll put those around my 30 degree angle duct pipe that is already drilled together. I'm just concerned the higher temp and pressure will blow the duct pipe apart.
If it gets too hot on the stove on the top then it's a problem - like 700 F is too hot as it would glow red and weaken over time. I got a tow chain 3/8 inch also to use as a thermal mass on top of the stove plus a 4 gallon pot of water.
So hopefully the exhaust will cool off enough by going up front through the two baffles and then back to the collar - by having those two baffles with the preheated secondary air. It's a five inch collar that increases to 6 inch stove pipe.
So as per your "rocket stove" flow area - I would need 19.625 inches flow rate area but I don't think I'll have even 1 inch of space between the baffles and the flue collar - with 11 inches wide - but it's 18 long. ... so should be fine - for flow rate...
Hopefully the secondary air will suck the smoke to the back of the stove - instead of back draft when I open the stove door.
We always wrapped a nice thick tow chain 3/8" or bigger around the
bottom 4 feet or so of our flue pipe, it threw a ton of heat and we
checked/cleaned our chimney twice a year! It always added to the heat
output and didn't ever cause any condensation or issues. But , then
again , we used common sense and checked and maintained our stove &
pipe regularly... The chain always let enough heat sink into the pipe to
burn off condensation, but also threw more heat than the pipe alone
did...you see, the chain allowed 'convection' to spread the heat, but
the stovepipe stayed hot enough to burn off properly.
I don't think I would conclude any secondary air is what is cooling off the exhaust; but that the heat is being conducted into the material of the stove above and to the sides of the insulated burn chamber. That improvement is resulting in only using about half as much fire wood as before. If more secondary air would be what is cooling it off by mixing in with it, (if that's what you mean) and going out the chimney; I wouldn't be seeing the improvement. When the exhaust goes out of the burn chamber, it spreads out over a large surface area and conducts heat into it. -that has always been my view. It's a hotter fire, but a smaller size fire now, then before the insulated burn chamber was added. I think the BTU's are about the same as before, just more heat is kicked out the front. Less heat is going out through the stove surfaces. -that's what I'm observing.
@Double M Innovations Thanks for your explanation. I know when I burn my stove with the front primary air fully open then the back top of my stove will glow red. I just have a steel baffle. So the exhaust leaving my stove is at least 600 F. with the top back of the stove before the collar - probably 800 F. When you say "heat is being conducted into the material...of the insulated burn chamber" -
I think what you mean this:
"Ceramic fiber board is thermally inert -- it does not absorb heat on the way up and does not release heat on the way down. This will generally allow for more firing cycles per day as you do not need to allow added firing time for the heat absorbed/released by regular clay kiln shelves or to avoid thermal shocking clay shelves."
The big dense firebrick obviously absorbs the most heat and also the two big stainless steel baffles absorb heat. So you are referring to all the dense firebrick absorbing heat - all those big dense firebricks. Less so the cheaper pumice firebrick. The steel obviously absorbs the heat of the exhaust - as the exhaust goes between the steel baffle and the ceramic fiber board. The secondary air tubes are below the steel baffle but are fed by the secondary air chamber between the lower and upper steel baffle - going off to the sides and then into the secondary air tubes. So the steel is absorbing the heat and the exhaust is burning off in the burn chamber and secondary burn and tertiary burn - and so it cools off due to that combustion process with the heat absorbed through the steel and firebrick but NOT through the ceramic fiber board.
So obviously if you are reading about 450 degree F. maximum on the top of your stove and 1400 F. maximum in your insulated fire box then you have an amazingly dramatic temperature difference. Yes the fire brick absorbs the heat but the "rocket" flow rate causes your exhaust to exit as a very high temperature - just as in a rocket stove.
That was my initial concern with your stove - somehow there HAS to be a dramatic cooling down of the exhaust before it hits the top steel of your wood stove - because a red hot glow of a wood stove means the strength is deteriorating over time and can crack.
So I'm sure having a Double Steel Baffle can absorb a lot of heat but also the air is absorbing a lot of the heat. The fact that the baffle is STAINLESS steel makes a huge difference as Stainless steel can handle a much higher long term temperature.
In rocket stoves - the secondary air is NOT used because it would cool down the burn chamber too much! So that is why I am claiming that your secondary air also cools down the burn chamber.
In Peter's Batch Box rocket mass heater his "P-channel" is based on a kind of baffle (called a heat riser port) that slows down the exhaust. So the air is preheated from going through the top of the stove but it has to be fed into a slow down in the flow rate. This is what creates the infamous "double horn" vortex as an "after burn" effect in the base of his Batch Box - it is precisely his secondary air that goes against a lower flow rate. Then when the riser turns 90 degrees that forces the flow rate to slow way down and the air then mixes with the exhaust for the reburn.
"For secondary combustion air to be most effective, the air is injected at a point in the fire box that best makes use of turbulence....This narrowing creates a Bernoulli effect, in that the gas velocity goes up temporarily accompanied by a pressure drop. So it will suck in air from behind the plate, cooling the plate and the first firebrick in one go."
So that is also what's happening in your stove.
The dimples act, in effect, like a trip wire. They promote a transition
to turbulent flow. By doing so, we get higher skin friction (yet another
name for viscous losses). BUT, remember the definition of a bluff body?
A golf ball is a sphere - and spheres are bluff bodies. Most of their
losses come from the wake - so if we can move the wake further back, we
can reduce the wake size and reduce the losses from the wake. It just so
happens that by increasing the turbulence, you decrease your drag by
reducing where most of the drag is coming from - flow separation (wake).
https://ecomodder.com/forum/showthread.php/crash-course-aerodynamics-introduction-turbulence-1132.html
The explanation for the lack of corrosion is that the inside of the
duct is cooled by the incoming air. And the duct itself is in an oxygen
poor corner of the firebox while the burn is going on, steel won't
corrode in the absence of oxygen.
So, this is one of the few steel parts inside the firebox which isn't
destroyed in ten runs, durability is reasonable. My next channel will
be made out of stainless steel 304, life time expectancy should be even
better.
https://batchrocket.eu/en/designs#pchannel
