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[Scott7m]

Ok...  I've got a situation i'm trying to work out here.  This customer has a stoker coal furnace, big cast iron burn chamber that has 3-4 air tubes that travel the full length of the burn pot.  This coal stoker gets so hot, you dont wanna stand in front of it and the cast iron turns red.

Its located in the garage 180 feet from his home, I know I can get the heat to the home, but how do i capture it....   Here is my thoughts.....  directly in front of his air ports on his stoker, which is driven by a big fan, there is just enough room to place a 15x17 heat exchanger.......  in this case a heat absorber lol 

Sooo.....   If he tries to keep his garage 75, where this is located, the fan should have to kick on enough to be putting a lot of heat through my coil. 

other thoughts/problems/ideas

can i utilize a hot water tank to gain some water capacity? 

If i use an isolator valve with fill up port to put water in the system, how do i regulate the pressure?  ORRRR how can i make it a true open system?  i thought about putting a T at the top of the system and running a piece of pex straight up on the suction side and let the water rise in the pipe as it got hotter, i'm not sure how to do an expansion tank in this case?

[martyinmi]

Scott,
   How old is the stoker? If it's very old and inefficient, a man of your caliber should be able to easily talk him into one of your stoves! Seriously though, it sounds like a lot of work for you in that he essentially wants you to make a boiler out of a burner. How hard would it be to plumb in some heat exchange tubes that you could circulate water through and into an external storage tank? A big issue that I can see might be excessive water temperature in the event the house doesn't use as much heat as the garage. Or could you set up water to air exchangers in the garage too, then maybe have a couple hundred gallons of storage capacity that thermostatically controls the damper on the stoker. I'm assuming his stoker is forced air.
   Sounds like quite a challenge. Commission on a large OWB would  require a lot less work and thought!     

[Scott7m]

It's a good stoker, fairly new.  He won't buy a boiler, he knows that I'm theory it is possible of making wayyy more btu's that the garage requires and he wants to send some of those into the home. 

 My first thoughts were tubes filled with water but the whole thing is cast iron and really no where to run them, I'm curious to how much heat I can pick up, the air out the front of the stoker is generally so hot yo u won't stand close to it

[martyinmi]

Is there room for you to hang small water tanks in strategic locations on the stoker to collect heat, then circulate the water from them to a larger insulated tank, then pipe it to the house? I built my brother a small tank(2"x15"x24") out of .125 metal that he hangs on the side of his pellet burner in his basement. It holds about 3 gallons of water that he circulates through 150' of half inch pex that is fastened to his floor boards under his kitchen and bathroom. When the burner is circulating the water in the pex is only about 95*, but he claims his room temperatures in those two zones stay 3*-5* warmer. Your project actually sounds like fun.

[Scott7m]

Oh my, hope my dad doesn't read that about the pellet
burner, he's messin with his to do what you did.

As far as water tanks on it, not really, it's an enclosed unit, he wants it to remain "factory looking" that's why I have to put a heat exhanger down in the space provided,
or at least try to!   

It is fun, and a challenge, a chance to learn something, so I'll try it. 

If use an 80 gallon water tank for extra capacity, is there any way to utilize an
expansion tank to control pressure build
up

[RSI]

Is there any chance you can post a picture of it?

[Scott7m]

Is there any chance you can post a picture of it?

not at this time.....  he lives in the next town over, i've been there to look at it but thats it.. 

I to have thought a bout copper around through the air ports it already has but I donno, it looks like a heat exchanger down in front of them might be the best, it would be sitting right near where the burn pot turns red but not touching it. 

[Scott7m]

Project complete....  Success

Ok..  So, after much thinking I decided to place a 16x18 heat exchanger in front of the air tube that pass through the firebox of the stoker.  I installed it inside of the cabinet/frame of the unit and the fit was near perfect.  Beside the stoker we mounted a 55 gallon hot water heater, it sits roughly 4 feet off the floor. 

I took out the drain and put in a 4" piece of black pipe and mounted a wasser pump on the the nipple as well as an isolator valve with water hose connection.  At the top on cold side was where my red or hot pipe first went from the exchanger in the stoker.  Also on the same wall I mounted a 20 plate for hot water in his shop.   Out of the top of the tank on the hot side I had a piece of clear tubing 1 1/4" diameter feed up about 5th into a catch tank.     

So let's simplify this..   Water enters the heat exchanges in the stoker, travels through a 20 plate and then into the top cold port of the the tank.  The pump pulls out of bottom and through the drain into the pex time saver pipe, it then travels 190 feet into a 1600-1800 sq ft home and through another 20 plate exchanger and a 16x18 in a forced air furnace.  Then back to the shop to the stoker. 

The questions I worried about was how could it be regulated? How much heat could the heat exchanger in the stoker actually absorb?  Would it work?

Well, it works and works amazingly well!! The regulation factor kinda takes care of itself, as the garage needs more heat, naturally the house does too. So that's not been an issue in our experiences so far.    As far as temp of the water, it's not as high as we see with our boilers but it is enough and is working well.  After a week the water checked by a heat gun on a pipe has averaged 147. Even this temp the water in the home "domestic" is slightly hotter than before and the temp out of the registers has went up over 15 degrees.  The customers are thrilled and can't believe how great it works!  I guess there is more than one way to skin a cat lol