heat exchanger

[laketom]

Hi to all:: OK.. In my infinite thinking brain, here goes:: I have a LP forced air furnace in the garage with AC coil along with a forced air wood burning stove. So now, I bought a outdoor boiler. So here's my thought:: Can I use the current coil in my LP furnace as a heat exchange coil??

I'm not a professional wood burner and new at OWB. So just checking for help

Thank you all!

 

[motoman3b]

dont think the manifolds are set up large enough to flow enough water to make it efficient

 

[Whitespider]

No... at least not without some heavy modification.

 

[CoreyB]

I was going to ask a simular question. Wharf about a small radiator. Like one off a motorcycle or transmission oil cooler.?

 

[stihly dan]

Your ac coil? An lp furnace should not have a water coil.

 

[CoreyB]

So adding a small radiator in the return duct is not ok? Any reason specifically not to.

 

[Whitespider]

So adding a small radiator in the return duct is not ok?

Why would you put one in a return duct??
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[Iska3]

You want to use the AC coil as a Heat Exchanger coil? Why put it in the return line?
Some say that the AC coil does not have large enough flow tubes so your BTU's might be restricted. My plate exchanger has small tubes so I have 22 psi pressure on my pump side and after a log period of time the hot water will cool down some but this is a small plate and only use for hot water. I have a large heat exchanger in my furnace also. Well worth the money and you only need to do it once. My friend took a oil cooler type radiator out of an old D8 cat and he had that as an exchanger in his garage. In his shop he used an old car radiator with a fan behind it and that works well. Most will work but keep in mind that with a lot of restrictions you put a pressure on your pump and you might not get the BTU's that you want.

 

[Whitespider]

The problem with an A/C evaporator (the coil inside the house) is it's designed to flow low-side (low-pressure) gas, not liquid.
Also, it will likely have some sort of metering valve, orifice tube, expansion valve, or other type of restriction(s) built into it.
To make it work as a liquid flowing heat exchanger you'd probably need to do some cutting and soldering/brazing to get the unrestricted flow required.
The A/C condenser (the coil outside the house) is designed to flow liquid.
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[Iska3]

I agree with Spidy. Some coils have a flow control inline but even then the flow is less and you will not get the BTU's like you think you should. It's not worth the efforts.

 

[NSMaple1]

What is a 'forced air wood burning stove'?

If there's something there already that burns wood, can you just use that?

Running good underground pipes from an OWB usually isn't cheap & easy. Or if it's done cheap & easy will send a lot of heat into the ground.

 

[stihly dan]

So adding a small radiator in the return duct is not ok? Any reason specifically not to.

That would be ok. I was stating that a lp furnace has a flue gas heat exchanger. You can have a water coil in ductwork but it is not typically found in an lp furnace. I think he was asking about his evaporator coil.

 

[CoreyB]

That would be ok. I was stating that a lp furnace has a flue gas heat exchanger. You can have a water coil in ductwork but it is not typically found in an lp furnace. I think he was asking about his evaporator coil.

Ya I did not realize that his questions where different then mine I was just trying to save an extra thread.

 

[stihly dan]

Ya I did not realize that his questions where different then mine I was just trying to save an extra thread.

It would be best to put it in the supply, having hot air blowing over the fan motor will shorten its life.