# hot water thermosyphon



## MELOC (Sep 26, 2005)

right now i am just using the water heating coil in my wood/oil furnace as a pre-heater for the electric water heater. i have decided i wish to try to hook up to the water heater's drain port and thermosyphon the hot water through the furnace coil.

the top of my water heater is higher than my furnace coil and the drain port is lower than the coil. i am hoping it would work ok without a pump. i think it is worth a shot.

my concern is regulating the water heater temperature. right now, i have the furnace set the cycle heating water and also utilize the oil burner from a low of 145 to a high of 165. well, i guess the water will cycle at a low temp of 145 and the oil heats to a high of 165 if needed. i have overload circulation when the wood heats water to 180. 

my concern is that the water in the water heater could heat to a potential 170-180 range on a warm day if the fire is not regulated well by the auto-damper.

my plan was to use a thermostatic valve to shut off the water return from the water heater and stop the thermosyphon. i would probably like to set that between 135-150 tops.

i would prefer a non-electrical valve but would use an electric valve if i have to. where should i shop for valves? 

i am also considering using a bypass valve and makeing the furnace coil a second heating circuit for a room that is not heated by the furnace currently. i figure i could use an automobile heater core, a coil of copper or another type of heater like a baseboard heater or an old school bus heater. i should keep it clean though, so copper coil or something else new and compatible with potable water should be used.

any thoughts or suggestions?

thanks


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## WisJim (Jan 14, 2004)

If you stop the thermosyphon and are still applying heat to the coil or loop in the firebox, the water left in the loop or coil will boil and you will get some odd burping etc in the coil. Don't impede the thermosyphon at all. It would be better to have a pump come on when the temp in the storage reaches a certain point, to circulate the water through a floor coil or radiator, to disperse some of the excess heat. I am using a 55 or 60 gallon electric water heater (not connected to electric) as a preheater/storage tank, thermosyphon circulation to a loop in my wood furnace. The thermosyphon works fine, and if I get enough hot water I will add a pump to circulate to the in-floor coils that are in my sun room floor. If you had a radiator or coils of copper to disperse heat, you could use thermosyphon effect to circulate the water through it, too, if you arranged the piping etc with that in mind. I think it would be best to make it all non-electric if possible (I'm going to try my set-up without a pump first, to see if it works). I just installed my new wood furnace with a water heating coil this fall, so it hasn't worked through a heating season yet.

I have my cold connection to the furnace water heating loop connected to the drain of the water tank, and I took out the top electric heating element and have my hot connection to the furnace loop there. I used a cross tee at the drain so I could also hook up a drain valve and a return connection from my in-floor heating coil there.


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## MELOC (Sep 26, 2005)

thanks for your reply

the water jacket on the furnace should overload cycle at 180 degrees dumping heat into the radiators of the house. the only time i am really S.O.L. is if the power goes out and the pump cannot circulate the heat. it actually happened once. i walked in just in time to drain the water jacket as the system was starting to boil and get dangerous.

i really just want to keep the water heater at a reasonably safe level. no need to have anyone get scalded. really, 135 is probably too hot.


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## WisJim (Jan 14, 2004)

I re-read your messages, and realized that you apparently just have one tank, your electric water heater, not 2 tanks like I have. I would suggest having a second tank that is actually heated by the wood stove jacket or coil, as a preheater tank for your "regular" water heater. It would save a bit of energy in the summer when the furnace wasn't running, too, by allowing water to warm up closer to room temp before going to the water heater.


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## Al. Countryboy (Oct 2, 2004)

I also have 2 water heaters. One on each side of my chimney in a small room. Cold water comes in where the drain was. A pipe connects where the bottom element was and goes through my chimney about where the heat from the heater inters into the chimney. This is a pipe that is about 1 1/2 inches. I used those metal mesh hydrolic line that are flexable that run to the bottom and top of the pipe going in and out of the heater. This makes hooking up much easier. This pipe is about the lenght of a hot water heater. Then another elbo at the top and reduced back down goes back through the chimney where the hot or cold water originally came into the heater. The hole at the top is where I run my pipe that goes to the cold water side of my heater (with elements) on the other side of the chimney. During this time of the year, I know my electic heater doesn't kick on very often. Sometimes my wife will say that the hot water isn't real hot. I grin and think to my self that this is because heated water is entering into the other tank at a temp. that does't let the element kick on using all that elect.  When clothes are washed or baths the elements do kick on and the water is warmer, but just hand washing and a few dishes I don't think it ever kicks on. One problem I had for a while was that the heating and cooling of the pipe inside the chimney caused the elbos to leak some, but they finally sealed off. The galvinized pipes going into the chimney are 3/4 inch at the top and bottom, then steps up to a 11/2 inches in the chimney the elbo and reduced back down to another 3/4 inch pipe going out. The hydrolic lines attach to these then to the heater. Installing the pipe would be a bit hard if your chimney is already built. I installed mine when I built it. It has been in use for at least 8 years and I know that we have save $$$$$$$ with this method. Even in the summer I feel that the water in the first tank probably warms up some before it goes into the second tank.


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## Abe R Crombie (Mar 13, 2005)

I am working on a loop to run from the kitchen range upstairs to the(electric) HWT downstairs.The hot water first has to rise,then cool to drop(very slight temp. difference)I used heater core on a 3/4 copper pipe at the top of the loop and some on the run down.At the highest point you need a air bleeder vent,or air in the line will stop the movement.The loop is about 24FT in length and I have had hot water return back to stove.I am going to be working on it this winter again as I haven't been able to get warm-hot water into tank.I will be trying a mixer pipe to achieve this.It will be totaly self sufficient...just add wood,
Abe


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## WisJim (Jan 14, 2004)

Abe,
For a thermosyhon to work the heat source needs to be below the storage tank. If the system you describe works, I will be surprised. Remember that warm water rises, and col water falls or sinks, and it sounds like you need warm water to sink, and cold water to rise for your system to work.


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## Abe R Crombie (Mar 13, 2005)

Hi Jim,
Yes I have been working on this for some time,with help from a good fellow from Maine through e-mails and pictures.He has provided me with good information and to date I have the hot water going down about 12 feet to the HWT and the loop back up to stove.Takes about 20 minutes from start to get hot back up to stove.I will be working on getting it into the tank this winter.
To get hot water to drop it must first go up2-3 feet,cool(through heater core on the line at the top and part way down)It has been working so far.
I will let you all know how I make out,
Abe


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