Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: sceptre74 on November 13, 2011, 05:36:29 AM
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I've lurking around this site for a few weeks and I must say that it's awesome. So much good info for someone that is new to the game. I don't have an owb as of yet, but i hope to be building one in the near future. I have an indoor forced air wood system now and I will obviously be putting a water to air exchanger in the plenum. What I'm thinking of doing is getting the exchanger now and plumbing it in to my electric dhwh by hooking into the bottom drain and the pressure relief valve with a circulating pump in there possibly wired into the furnace fan so it only runs when there is enough heat to properly heat the water. Power rates aren't getting any cheaper these days. Lol. Does anyone think this will work and would it be worth my while? Thanks
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Welcome to the site, I don't know if the cost to reheat the water in the hot water heater would be cheaper than running your furnace (gas or electric) but I have thought about this in the past. It would be a good test.
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It is actually a wood furnace so it wouldn't be costing me anything extra. I figure if the pump is controlled by the fan, it won't be circulating cooler water through the dhwh. I'm just wondering what size hx I should get. the plenum is 24 x 29 and the btu output 110000.
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Welcome!
The smallest recommended on here is a 20 Plate. (Or sidearm). 20 plates offer the least (minimum) amount of restriction for water flow.
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Does anyone think a water to air hx could work in reverse the way i'm planning on using it? Would the heat from the furnace heat the water enough to make it worth my while to try this?
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My home built OWB feeds an 18 X 18 heat exchanger in my oil furnance plenum. When I go on holidays, the OWB is shut down of course and the house is heated by the oil furnace. Because the circulating pump for the OWB is left running, heat effectively flows in reverse and is transfered from the oil furnance, into the heat exchanger and to the OWB. The temp of the OWB reaches about 70 to 80 deg. It is for this reason that I do not use glycol with my system.
My OWB is 160 feet from the house and contains 600 gallons between the boiler and storage tank. My location is central Ontario.
In your case I would think it would help supplement the hot water temp but may not be enough on its own. You will be buying all the needed parts when you build your own OWB anyways so it would cost you very little to try it. Hope my .02 cents helps.
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OK I think I understand what you are wanting to do now, use a water to air HEX to heat water going into your water heater. Is this correct?
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Sounds like it would pre warm the water so the water heater doesn't have to work AS hard to heat it, but I seriously doubt it would heat it enough to keep the element from having to kick in.
My humble opinion.
Welcome to the family
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Yes bull, that is exactly what I want to do. I'm pretty sure it won't heat all the water, but if it does pre warm the water it should make a bit of difference in the power bill. I've got three daughters and I can just imagine how much hot water they will be using as the get older. Can't wait to get my owb built and running. Lol
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A side arm on the side of the tank probably wouldn't work very good.
If you put a plate heat exchanger in series with the cold it should though.
One possible problem is that you really have no control over the temperature and you don't want it boiling the water in the heat exchanger. If you put a recirc pump on it and have it pump through the tank when it gets too hot it would help.