Domestic Water Heat Coil Size

I am installing a Leisure Line Pocono.
I am building a jacket to tie into the heating system via the cold air return. My design is based on this idea:
http://www.leisurelinestoves.com/1904137.html

I have remove the "Lid" so the top of the burn box is very accessable.

This allows me to easily place a copper coil on top of the burn box. I plan to use 5/8 soft copper pipe to make the coil, and for the send and return from my existing 40 gallon hotwater tank.
The outlet in the existing tank will be the drain, the inlet will be at the pressure relief valve entry. The pressure relief valve is about 1 inch higher that the top of the stove where the coil will be placed.
I will try natural convection for the water transport, but will add a circulating pump if necessary.

Now, if the above doesn't make alarms go off in your head, my question is, how many feet of the copper tubing should be used for the loop.

Thank you
Don

Hello Don, you are planning on keeping the Pressure relief valve operational aren't you??

As for how many loops of copper to put on the top of the stove, I really do not know. I'd try about 3-4 and see how it works.

The inside the stove loops are a 'U' with a single pass over the hot 1500* fire. The top of the stove is probably around 250-300*, so you may get enough heat to effectivly heat the water with three loops.

It's going to be an interesting experiment..

Greg L.

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I would be leery of using soft copper. Even with a PRV, that tube can become a pressure vessel in a heartbeat under the right conditions. Soft copper has a low enough bursting pressure, I think it will drop like a rock with the temps it will see in a coal appliance.
My $.02.

Ian, X wants to put the coil on top of the stove on the outside of the box, do you think 2-300* will weaken soft copper?? If so, which SS will bend like soft copper so X can wind up a coil??

Greg

LsFarm wrote:do you think 2-300* will weaken soft copper?? Greg

300* will probably cut it 1/3? Outside the firebox should be OK. I would enclose it though.

Wow, I didn't realize it was "THAT' soft. What SS tube would be better suited for the coil??

Greg L

The reason I am thinking of a copper coil on top is that no one had a SS coil in stock. But looking at the weather report, it appears I have 4 days before the day time temperature will be below 60. I should order one today.

Thanks for the help

Don

I would expect soft copper to work harden after repeated heatings to temps over 5-600* (inside the stove), at that point it may just crack off near its fittings. Outside the firebox, it would not see those temps so it probably would not be an issue. I wouldn't use it myself though.

3/4" or 1" 304L 16Ga tubing will work well but it will require a bender rated for a 6'- 8' handle to be attached to make the bends. A hydralic bender is even better. Stainless tubing bends very hard with the exception of 303 and 303L but it doesn't have the burst strenght required . It would be easier to bend type L copper to make the coil. If you want to put it inside only type 316L stainless will do. Make sure it has the L on the end. They sell/make plain type 316 tubing/pipe and it has 3X the amount of carbon as the 316L so it is less heat and chemically resistant to the by products of a coal fire. We have run 150lbs steam through 16ga tyep 316L for years with no problems with corrosion.

Stainless steel tubing can be found at mcmaster carr. 304 welded tubing in 5/8" is $17 for 6 feet. Not to mention the cost for the parker or swedgelock fittings that you will need. So I think that it will be a little expensive for what you want to do. I think copper will be plenty strong, easier to form, cheaper, and have better heat transfer than ss.
The soft copper that they have listed has a .040 wall thickness and 501 lb working pressure. Most home water pressure will never exceed 60lbs. The temp of the copper should not exceed the temp of the water it contains. So I would say if you put a small pump on the line you will never have to worry about the copper getting to hot. You can look up the properties of the tubing you want at mcmaster carr They may also have a pump but I am not sure. Others may know a cheaper place to get a pump. I just thought of something else, the copper tubing that they sell at home depot and lowes is thinner wall so I would avoid it unless it says it is for refrigeration. I hope this helps.

xackley wrote:I should order one today.

Don, did you ever end up ordering the coil? Looks like we have nice warm weather for a while yet.

Nope, I looped some copper and will be waiting to test it out. But the more I think about it, the less optimistic I am. But there is no way to know for sure until this summer weather ends.