# Fireplace construction



## bytor (Jan 23, 2010)

Thank you for sharing those pictures Francis.... Sure helps to explain things.


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## Fancis Casini (Jan 31, 2013)

re;Thank you for sharing those pictures Francis.... Sure helps to explain things.

that damper I first made around 1986....and then I made another for my house never realizing its potential.....I'll sometimes get slight eddys and it scared me at first....so I took a wisk brush and cleaned off the blade and front skirt...instantly stopped with a 1-3/4'' by 47'' ...smooth plate helps too. Watch hen u but a plate for the damper....many times they are bent.
I cut them with the demo saw and if bent trhey can be straigtened with some heat and pressure. It's been a while but I think I put some insul at the ends of the lintel for expansion....Ive had 12 and 14'' logs blaring with not one crack.....however the lower f box is rapidly spalling due to much less room air hitting it and cooling it.....ie if I burn for 12 hours I'll get nearly 3 days radiant heat from the masonry in the imediate room as well as the dinning room which is at the back side.

My woodstove has been rusting for two years now.....we love the fireplace now more than ever....no more drafts and cold backs.


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## dom-mas (Nov 26, 2011)

Installing the damper on top of roxul...forgot about that. Hope i remember again by the time i do the next one


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## Fancis Casini (Jan 31, 2013)

dom-mas said:


> Installing the damper on top of roxul...forgot about that. Hope i remember again by the time i do the next one


Sean no.....I meant at the ends of the long outer L..or just rake out some of the mud.


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## dom-mas (Nov 26, 2011)

Anywhere that has steel and can get hot is a good area to lay the steel on some roxul and a bit on top, somewhere for expansion...I'd forgotten about it


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## Fancis Casini (Jan 31, 2013)

dom-mas said:


> Anywhere that has steel and can get hot is a good area to lay the steel on some roxul and a bit on top, somewhere for expansion...I'd forgotten about it


Sean it's a triangular load bearing lintel....been time proven under rigorous 40 and 60 hr burns for 22 years ,the last 2 being at 1-3/4'' throat where the breast gets pretty darn heated.....at each end is sufficient of the lintel is good the back piece at the firebox is cut a tad shorter than the box side walls front to back I did nothing however a piece of sill sealer can be placed on the fireback and let be burned out whatever.


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## Fancis Casini (Jan 31, 2013)

bytor said:


> I always thought this was not good practice...?
> Of course I can't find the article just now, but read a while back that the turbulence caused by trying to direct the gasses into two flues was so great that it reduced the effective flue size to the equivalent of only one of the flues.
> 
> P.S Francis, I'd love to see some pictures of one of your dampers if you're willing to share...


Bytor / J this basically what I've said and more per the thermodynamic aspect of double pipes equalling a single larger one. 
Again same lengths and hieght, a plenum being the smoke chamber,while cutting the inside adjoining flue wall at the top by 8'' or so is even double insurance.

The thermo explaination says making one hotter than the other to draw more is moot being at equal lengths extra heat would need to be generated without work.....impossible . Note I said keeping the flues together originally which means equal in temp....if masonry is less around one than the other and on a exterior wall it could lessen flow in the colder flue during non wind only...but that's highly hypathetical however one never knows what the trowel man is thinking!:whistling 

I posted a similar post on the Rumford Blog in a rebuttal to Jim Buckley's disapproval of two identical flues for a fireplace! He also is bent on straight back firebox supremacy still, yet the ratio is in my favor by 50%

Perhaps He and J can come over for a live tutorial....we'll put it on you tube at a later date......What better advertisement :thumbup:

Buckley thinks I'm just a mason.....heck my first fp was in a undergound fort ...we put a bag of portland on our bicycle and wheeled it up main st ......then the old man comes by waiving that hand 

I have another question about the bernoulli equation. Let's says that I have a 200 gallons per minute flow on a 5 inch pipe and at 26 psia then the flow is divided equally into 2 pipes (each with a 2 inch diameter). And I wanna know what is the pressure on those 2 pipes. We can ignore any friction losses. All 3 pipes have the same elevation. I want to know if my bernoulli equation is correct

(P1/density)+((V1^2)/2G)=(P2/density)+((V2^2)/2G)+(P3/density)+((V3^2)/2G)

Where 
P1 is pressure on the main pipe (the 5 inch pipe)
V1 is the velocity on the main pipe
P2 pressure on one of the 2 smaller pipes
V2 is the velocity on on the smaller pipes
P3 pressure on one of the 2 smaller pipes
V3 is the velocity on on the smaller pipes

Those pressure, flow and velocity numbers are made up. What I really wanna know is if the bernoulli equation above is correct fore this system, where a pipe with a given diameter is divided into 2 other pipes with a smaller diameter. And the flow is split in half between the 2 pipes.

http://lofi.forum.physorg.com/bernoulli-equation-for-split-flow_14070.html

Can someone tell me if I'm right?
mr_homm
11th April 2007 - 02:23 PM
Unfortunately, that is not correct. In fact, Bernoulli's equation is NOT sufficient to determine how the flow splits into the two pipes, because the flow in each pipe also depends on conditions downstream of the split. For instance, if one pipe is partially clogged later on, you will see less flow into it here at the junction.

Here is an analogy which may be useful in thinking about these problems (assuming you are familiar with electric circuits). The Bernoulli formula B gives the energy per unit mass carried by the flow, just as the voltage gives the energy per unit charge carried by electric current. The mass flow rate m' acts just like electric current I, in that both mass and charge are conserved. Power carried by the flow is B*m' and power carried by an electric current is V*I. Current splits when two wires are parallel, and mass flow splits when two pipes are parallel. The voltage drop across two parallel wires is equal, and the drop of B (head loss) across two parallel pipes (i.e. they split and then rejoin later) is also equal. Voltage changes across two resistors or batteries in series sum up, but the currents through them are equal, and head changes across two clogs or pumps in series sum up, but the mass flows through them are equal.

The analogy is quite exact, and all the same kind of reasoning can be applied. In the case of your branching pipes the analogy would say that since the voltages of three wires that are joined at a point are all equal, then B in the three pipes must all be equal at the junction (though they may change later due to clogs or pumps). This means that you DO NOT ADD the B values for the two smaller pipes. Instead, they are EACH equal to the B of the larger pipe. Therefore, your equation should read:

(P1/density)+((V1^2)/2G)=(P2/density)+((V2^2)/2G)=(P3/density)+((V3^2)/2G).

You will also be able to apply the equation of continuity, m'1 = m'2 +m'3, which in terms of velocity is v1*A1*density = v2*A2*density + v3*A3*density, where A is area.

There are 4 unknowns (two velocities and two pressures) but only 3 equations, which is why more information about conditions downstream is needed, just as with electric circuits.

By the way, many people make the mistake of thinking the pressure must be equal in all 3 pipes. This is not true. B must be equal in all 3 pipes, because it represents the energy per unit mass carried by the flow. If B were higher in one exit pipe than in the other, then it would also be higher than B in the inlet pipe (since the average value of B in the inlet and exit flows must be equal by conservation of energy). But that would mean that you could concentrate energy into one flow without doing any mechanical work. If that were true, you could build a system that would violate the second law of thermodynamics, by using heat o drive the flow in the first pipe, then concentrating the energy into one flow, and then converting it back to heat. Since there would be more energy per unit mass, the final temperature would be higher than the initial temperature of the heat source that was driving the flow, so you would have made heat flow from a cold temperature to a hotter one with no applied work. If that were possible, I would already have patented it. 

Hope this helps!

--Stuart Anderson


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## Fancis Casini (Jan 31, 2013)

Here are some exterior pics I was sent. Could of been smoother inside the flue. He hired out the exterior work


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## Rockmonster (Nov 15, 2007)

Did you say he's a roofer, and he's working on his own home, and he's in his early thirties?

Boy, did *I* go into the wrong business......


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## JBM (Mar 31, 2011)

I love that roof line held up by a lally column. That wont crack.


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## superseal (Feb 4, 2009)

That's a bad azz roof...he's knows what he's doing :thumbup:


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## Fancis Casini (Jan 31, 2013)

Rockmonster said:


> Did you say he's a roofer, and he's working on his own home, and he's in his early thirties?
> 
> Boy, did *I* go into the wrong business......


Its all thin stone and not my cup of tea.....but this is his second home and it has no mortgage :thumbsup:He does roofing / remodeling as well as stamped crete.


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## Fancis Casini (Jan 31, 2013)

JBM said:


> I love that roof line held up by a lally column. That wont crack.


yes it will and its not due to strength, rather if it's steel there will be about an easy 1/2'' difference when the studs and joists dry.


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## Gordon Forsyth (May 18, 2015)

A real fireplace should be built by someone who knows what they are doing


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## Fancis Casini (Jan 31, 2013)

Gordon Forsyth said:


> A real fireplace should be built by someone who knows what they are doing


lol Real Fireplace? How do you build one?


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