Pre-heating (warming) water to water heater

[bigbadbob]

I built a pre heater for my hotwater.
I used a hotwater tank stripped for the preheat.
I bent two coils of 3/4 stainless (scrapyard, easy to bend). Welded that in my woodstove near the top.
Got a blowoff valve. Vented it outside.
Had the tank sitting so convection would circulate the water.
Worked very well.
Only had the water go back wards a few times, just use some up and it was fine again, man it makes a lot of noise going back wards.
Had it blow off a few times, have to get busy using up the water. Neighbors wondered what was going on with all the steam!!!
As I built it I had it check out by a friend who is familiar with furnace boilers etc.
Was amazed how much wood it takes to heat thae water.
Just do you homework and fly at it.

 

[timbrjackrussel]

Heating water Be careful

Read this, It can be done!!!
http://www.woodheat.org/dhw/dhw.htm

 

[2manytoys4me]

Being as an electric hot water heater can be 30% of an electric bill and the rates just keep going up through the roof, I'm thinking about doing things which will reduce my electric bill.

One thing is that the water coming into my house from the city is very cold...

And the walls surrounding my wood stove are very hot!

So.... I was thinking about installing an old fashioned steam heating radiator or some sort of coil of pipes going back and forth along the wall next to my wood stove. Then running the cold water from my main through this and THEN out and into the cold water inlet of my electric water heater.

So when burning wood, the heat from the wood stove would "pre-heat" or warm this water before it gets to my electric water heater. So less heating would be required from my water heater and a lower electric bill.

Anyone done anything like this?

(I don't expect this to get the water hot, just to warm it up a bit...)

sent you a pm

 

[Billy_Bob]

I've decided on what I am going to do...

I went and looked at solar water heating systems and they were about $6000. Solar systems basically pre-heat or warm the water in a separate tank and then the water goes from that tank to the water heater for additional heating.

Basically I have two sources of heat for pre-heating water. In the winter next to my wood stove and in the summer my attic gets to be quite hot.

So I am going to get two of those old steam heating radiators and set them along the wall next to my woodstove. Then run the cold water into the bottom connection of one. Then pipe from the top of that radiator to the bottom of the next. Then run a large 2" or so pipe out of the top of that radiator and back over the top of the two radiators (water will flow slowly to gather more heat from stove) and then transition down to a 1/2" pipe to go through the wall to my water heater.

My water heater is right behind the wall of where my wood stove is. I am going to elevate it so it is as high up as I can get it. Then run the 1/2" pipe from the radiators into the drain pipe on the bottom of the water heater. (Instead of running the cold water into the top of the water heater.)

Heat rises, so some heat may travel up the pipe and into the water heater. But at least the water will be pre-heated by the woodstove and warm water will be going into my water heater instead of very cold water. So less heating will be needed by my water heater most of the time.

This will work throughout the day as we frequently use small amounts of hot water for washing hands, doing dishes, etc. This of course will not work for long when taking showers as the hot water is on for a long period of time.

Then for the summer, I am going to run some large 2" plastic water pipes back and forth in the attic. (Water would flow very slowly in the very large pipes allowing time for the water to warm up.) Then divert the water coming from the radiators next to the wood stove up to the large pipes in the attic. Then the warmed attic water will then flow to the water heater. We get very cold water year round, so the cool water flowing through the radiators next to the wood stove will help to cool the room in the summer, then will be heated/warmed in the hot attic.

I'm using plastic pipe in the attic so I will be able to drain the water out of the attic pipes each fall to prevent freezing and so they will not rust on the inside.

And of course I'll need to install an assortment of pipes and valves to bleed the air out of the attic pipes when first running water into them in the spring. And to switch the attic system on/off/drain. And I will need to install drain valves at the low points of the radiators to flush them from time to time to remove accumulated particles which will be at the bottom. (Will work the same as a water heater drain.)

I would estimate this whole pre-heat setup will cost just a few hundred dollars.

In the future, depending on how this all works, I may get an additional insulated tank (maybe old water heater) and get a solar cell on the roof to power a pump to circulate the water slowly from the radiators/attic pipes to this "pre-heat" tank. Then I would have a whole tank of pre-heated water which would work for showers as well.

 

[geofore]

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Chit

To stop heating the water in your pipes and heat only the water in your tank, take the out flow line from your water heater up then back down 6"-12" (a loop) then feed the house hot water. Most folks don't know that because they did not put a 6"-12" loop in the hot water line after it left the water heater that the hot water flows up and heats the line and as the water cools it returns to be reheated over and over again. They are trying to heat their house using their hot water line as a heat exchanger. By putting a loop in the line it stops the hot water from moving out until it is called for. Heat rises, the loop prevents the hot water from moving past the loop and heating the entire line. I cannot tell you how many hot water systems I have fixxed because the installation was done without the loop in the line. you are wasting energy trying to heat your house using the hot water line as a heat exchanger.
For the cost of a few elbows you didn't put into a loop you are paying for the cost of trying to heat your house with the hot water heater. So either spend a few pennies on elbows and put a loop in the line or waste dollars trying to heat your house with the water heater.