Thermosiphon Question for Coil

traderfjp · By: **traderfjp** On: Tue Jul 29, 2008 4:41 pm

I would like to get water to circulate through a coil and into an oil fired hot water tank and back without using a circulator. If I hook up one end of the coil to the bottom of my hot water tank (tee off drain) and then hook up the other end to the top of the tank (tee off relief valve) will the water naturally circulate? Would I need a check valve? Enclosed is a diagram.

Richard S. · By: **Richard S.** On: Tue Jul 29, 2008 5:12 pm

You need the check valves to make sure the cold water goes through the coil first instead of going into the hot water heater. I believe someone mentioned a specific type that offers little resistance the way it allows the water to flow.

Make sure the hot water tank is as close to the furnace as possible and get it as high off above the coil as you can.

traderfjp · By: **traderfjp** On: Tue Jul 29, 2008 5:31 pm

I would say the applicances are about 4' apart. The coils are in the middle of the boiler and the relief valve is higher then the coil and the drain is obviously much lower. A check valve keeps the water flowing in one direction. I'm thinking that the hot water closer to the top of the tank would want to naturally flow through the coil and maybe put a check valve on this connection. Then the water would be dumped back into the bottom of the tank via the tee off in drain. Is this what u mean?

Richard S. · By: **Richard S.** On: Tue Jul 29, 2008 5:46 pm

The cold water comes in from the street, it runs throught the coil. the coil is connected to the top of the hot water tank. The drain on the bottom is connected back to the same pipe the cold water comes in:

http://nepacrossroads.com/kb/Hot_Water_Coil

Freddy · By: **Freddy** On: Tue Jul 29, 2008 6:52 pm

The check valves should be "swing checks". Ball checks or flow checks will not allow thermosiphon to flow.

Razzler · By: **Razzler** On: Tue Jul 29, 2008 9:31 pm

I think you would have to set it up something like this to get the hot water to circulate?? my 2 cents :notsure:

traderfjp · By: **traderfjp** On: Tue Jul 29, 2008 10:52 pm

I don't have the ceiling height to raise the heater.

Freddy · By: **Freddy** On: Wed Jul 30, 2008 5:59 am

Hot water will thermosiphon just fine with tanks on the same level, but, something I just realized and maybe should be said about thermosiphoning..... It works because heat rises. It happens fairly slowly. It's kind of like a helium ballon, when you let one go, it doesn't scream to the sky, it just kind of drifts upward. The larger the ballon, the faster it goes up. Same thing with themosiphoning (gravity hot water). It needs good size pipes. 3/4" I'd think minimum. And now the trump card.... Imagine in your head putting a steel ball bearing inside the piping at the highest point. Will it roll all the way to the lowest point? Will that happen in either direction? If not, the siphon isn't going t work very well, if at all. What I'm saying is all pipes should not go down hill at all and the coil in the stove should coil from up to down.
If not.... you'll need a bronze pump.

Sting · By: **Sting** On: Wed Jul 30, 2008 9:00 am

pump it

Strap on a Honeywell switch wired to open on temperature to limit the DWH storage tank to 125 degrees (code) or install a mixing valve on the supply out of the tank to protect the human pink parts :lol:

under the faucet!

traderfjp · By: **traderfjp** On: Wed Jul 30, 2008 1:53 pm

Sting: Your post is dirty: Pump it, strap on, wired (reference to drugs maybe) and human pink parts. Come one! :shock:

:

Richard S. · By: **Richard S.** On: Wed Jul 30, 2008 2:09 pm

Freddy wrote: I just realized and maybe should be said about thermosiphoning..... It works because heat rises. It happens fairly slowly. It's kind of like a helium ballon, when you let one go,.

True freddy but you're also sending all the water through the coil before it gets in the DHW. It's hotter than what the tank would make it before it gets there. Those hot water heater don't come on much, generally when they are in use. Realistically you could send it through the coil into the tank without the loop and still save a significant amount of money, if you use a lot of hot water throughout the day replenishing the heat it may even be the best option.

One thing to add one of the resons we have this setup is we can always have hot water as long as there is electricity. In the summer we shut the furnace down for at least a day...

Sting · By: **Sting** On: Wed Jul 30, 2008 3:41 pm

traderfjp wrote:Sting: Your post is dirty: Pump it, strap on, wired (reference to drugs maybe) and human pink parts. Come one! :

What is going on in your head?

http://nepacrossroads.com/kb/hot_water_coil

Sting · By: **Sting** On: Wed Jul 30, 2008 3:49 pm

Second thought....

Never mind

I REALLY don't want to know. :sick:

traderfjp · By: **traderfjp** On: Wed Jul 30, 2008 5:34 pm

Sorry Sting I got carried away. I read the Wiki on Richard's thermosiphon diagram and I created a diagram that I think depicts what the article was saying and perhpas may illustrate (crude I know) the concept. It's an intersting concept. Let me know if this is what the Wiki had in mind.

traderfjp · By: **traderfjp** On: Wed Jul 30, 2008 5:38 pm

Looking at this sketch I made reminded me when I drain my tank. I always have to oopen the relief valve to really get the tank to drain. I'm just wondering if this would work at all. hmmmm

Thermosiphon Question for Coil

Thermosiphon Question for Coil

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