Thermosiphon Question for Coil

 
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traderfjp
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Post by traderfjp » 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.

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Richard S.
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Post by Richard S. » Tue. Jul. 29, 2008 5:12 pm

Make sure the hot water tank is as close to the furnace as possible and it should be level or above above the coil.

 
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Post by traderfjp » 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?

 
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Post by Richard S. » Tue. Jul. 29, 2008 5:46 pm


 
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Freddy
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Post by Freddy » 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.

 
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Post by Razzler » 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:

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Post by traderfjp » Tue. Jul. 29, 2008 10:52 pm

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


 
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Post by Freddy » 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.

 
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Post by Sting » 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!

 
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Richard S.
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Post by Richard S. » 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,.
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 reasons we have this setup is we can always have hot water as long as there is electricity. In the summer we shut the boiler down for at least a few days...

 
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Post by traderfjp » Wed. Jul. 30, 2008 5:34 pm

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.

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Post by traderfjp » 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

 
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Post by mozz » Wed. Jul. 30, 2008 6:31 pm

I do know of a few people whom just plumb the coal boiler in series with the elec. hot water heater. Coal boiler first, outlet of coal to inlet of elec. Has been working good for over 30 years on both setups, original water heaters too, though they both expect the water heaters to die one of these years. Drain the water heater once a year and change the anode if needed. There are ball valves on the coal for bypass for when it gets shut down and cleaned once a year. I'm pretty sure that is how I am going to plumb my AA-130 once installed.

 
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Post by Adamiscold » Thu. Jul. 31, 2008 8:14 am

Trader,

I like the diagram, how would you draw it up if you had the water from main going into the tank first?

 
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Post by Richard S. » Thu. Jul. 31, 2008 8:57 am

Why would you send it through the the tank first? That really defeats the purpose of the hot water coal.


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