So our hot water heater is in the basement, just below our wood stove. I'm tossing around the idea of adding a loop on the supply side of the heater to divert water up to the wood stove, to preheat 52° water coming in from the street. 1) in the winter, the stove runs 24/7. This isn't intended to be used in summer, although water taking a circuitous course through the warmer kitchen might be useful. 2) copper pipe zigzagged across the ceiling above the stove is my instinct. Ceiling is open. So I have unlimited space to tinker with. A ss water bin/trough/tank could also be suspended between the joists I bet. 3) is a T&P valve a good idea in a loop like that (even though the hwh has one)? 4) or, would it be better to figure out a different loop to the tank and back, and run a circulator pump? I have not considered cost of said hairbrained idea over money saved yet....am aware this could get spendy. Sca
Do you have room for a small tank? I think a tank about 20 gallons might do better than a small loop that isn’t gonna do much when the cold water starts to flow where the tank would have 20 gallons preheated? Safety first with type of setup though! Good luck!
Pretty much the space between joists. Not sure what there is out there, perhaps will need those to fabricated. If I ran 4' runs, spaced half an inch apart, maybe 6 runs per bay in 3 bays....painted the copper black....might preheat a bit. Course the cost of copper and all those elbows might outstrip any savings in electricity. Till the electric prices go up... Sca
You are going to see VERY little gain from this...just not enough temp differential...plus copper prices... You'd be better off installing a HPWH and duct the intake/exhaust to upstairs for the winter, downstairs for the summer, so you can take advantage of the dehumidification...I installed one a couple years ago and see a $15-20/mo savings paying less than $0.12/KWH YMMV
Several years ago I had the idea of pre-heating water from the hose when we filled my in-law's swimming pool in the spring. I took a 5' section of 3" pipe, capped both ends and welded some hose fittings on it. I placed the pipe in the middle of a raging fire. I expected a lot more than what I got. It worked, but only kinda sorta. What you are describing would have very little impact on your energy bill, if any.
I have experience with 2 versions of robbing heat from wood stoves to heat water. The first one in the 70's was a welded steel tank behind a wood stove, The tank was tied to a 50 gallon electric water heater on the opposite side of the wall. Hot water from tank would rise into top of water heater and cold water from water heater would flow out of the bottom of the water heater into the tank. In the morning you had 70 gallon of really hot water. The electric water heater was turned off all winter when the wood stove was in operation. My Dad and a friend came up with the idea. I learned to stick weld when we built the tank. The second one I built after "acquiring" a 80 gallon heat exchanger tank from a Friendly's Restaurant fire renovation I did in the 90's. This tank has 4 separate loops in it that took heat off of the restaurant ice cream freezers to preheat water. I was installing water source heat pumps in Mrs PMM's family homestead to replace the ancient oil burners and electric AC units. The Florida heat pumps when operating in AC do the same thing as the ice cream freezers and I just happen to have 4 of them. So with the heat pumps in AC and all 4 running I'm preheating 80 gallons to 90 degrees on hot summer days. Back to the wood stove water heater. I ran 3/4 copper from the bottom of the 80 gallon tank to the top of the wood stove, built a 3/4" 4 tube manifold across the top of the wood stove and ran that to the top of the 80 gallon tank. I've had mornings where the 80 gallon tank is 115 degrees. Most mornings it's around 100. I think it depends on how much hot water we use the day before. So our electric water heater gets a 5 month break in the winter and 2 to 3 months in the summer. Bottom line. You need a tank and a heat exchanger on or in the stove.
You can get a stainless loop to install in the fire box of the stove. Then plumb it in. Mostly wood cook stoves use them. I've though about installing one with a range boiler. There's a few ways to hook up a range boiler without a pump. I guess US manufacturers aren't allowed to make stoves with hot water setups unless it's a cookstove. Other countries you can get them.
Those dang things are expensive and take up space in the stove. But they are supposed to work really well. I opted for 4 lengths of 3/4" copper pipe across the top of the stove since I had it from past jobs.
We can heat enough water for day to day needs on the cook top. I will think about utilizing that heated space above the stove a little further. Even a couple of ss tanks plumbed to the shower might be useful....even for one shower. Further mulling. Sca
Given the small savings I don't think it's worth it not just from the expense/ROI but also weighing the possibility of water born bacteria that multiply in stagnant unhot water. Probably less of an issue in a home with lots of peoples.
Like a valve getting closed or a pump failing? My Dad took the handles off the gate valves. I zip tie mine open when it's heating season.
