Another idea in hot water

[lectraplayer]

I'm working on a storage hot water heater from a propane heater (seperate thread) but am also wondering how much heat I can get from my Wonderwood 2600 with a collector coil in the top few feet of my stack. The stack is 10 feet straight up, and I'm thinking about a half inch dia. soft copper coil about 3 feet long at most, and adding a new 1 foot piece of insulated chimney to be placed as the top piece (and my cap on it) for this, sealing with fire putty. My questions include:

1) how many feet of pipe can I coil up before I kill my draft

2) how much heat can I get with a decent fire

3) where do I need my safety valve

 

[TCaldwell]

In theory it will work, however not practical for a cord wood fired boiler. As you touched upon the ammt of copper coil you would need in the flue to produce enough heat to charge a hwh will severely limit the overall boiler output from the reduced draft. The low temp inlet water will cause condensation on the coil reducing it's effiency. You might look for a coil location on a exterior boiler surface.

 

[lectraplayer]

I don't like the idea of wrapping the lower section of my flue as it would take away from my draft and be a creosote factory. I was hoping I could get my draft going and THEN collect heat at the top. Wouldn't I eventually get enough heat, though not all at one time after an all day fire?

 

[maple1]

It doesn't matter where in the stack you put it, with respect to limiting the draft. If it's going to restrict, it will restrict at the bottom or the top.

And will make creosote like crazy.

And it won't give you much extra heat. The first fire will make a layer of insulating creosote on it and pretty well kill that aspect.

 

[Bad LP]

I've also thought about doing a water coil on my flue pipe from the cellar wood stove as there is a lot of heat radiating off of it then pipe it to my fan coil unit about 25 feet away. It sure would be a fast way to send heat thru my AC ducts throughout the house for a fast heat up.

My thought was to spot weld a coil of pipe on the outside of some 8" (1/16-1/8" wall) pipe then cover that coil with a 10" section of pipe and cap both ends leaving exposed threaded ends for adaptors to copper pipe.

 

[hiker88]

I remember listening to the Hot and Cold radio show here in Maine one Saturday morning and a caller had the same proposal for Dr. Hill. If I remember correctly, Dr. Hill and his university students played around with the idea some in the lab but it wasn't practical in the end.

 

[lectraplayer]

The ultimate to me would be to have the water line coiled around the outside of the inner liner of the last insulated 6 feet or so of my chimney above the roof, that way everything can be fully burned by the time it gets to the collector coil. Since that's out right now, I'm going through a variety of ideas on heating water and (if I can) about 1500 sq. Ft. Of house.