Will a Gravity Flow Hot water heat system work?

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Old 12-05-07, 08:45 PM
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Will a Gravity Flow Hot water heat system work?

I want to install a gravity flow (no pump or electricity) system to heat a 1200 sq ft house. I will use an outdoor wood fired water heater that will sit about 25' away from the house and about 6' below the floor I want to heat. I have several cast iron radiators to use. I can run a pipe in at the top and out the botom. My plan is to use a 2" pipe out of the top of my outdoor heater and slope it up to the house. I would tee off of that to each of my raidators using 1 1/4" to 1 1/2" pipe and have a similar return line going to the botom of my outdoor heater. The heater will run at atmosphereic pressure with a stand pipe to keep the water level above the raidators.
My questions are; is anyone doing anything like this? Can I expect to get enough flow with no pump? What type of water, chemicals or antifreeze should I use? I dont want to have to wory about this system freezing if there is no fire. What potential problems may I face heating this way?
Thanks for any responces, Danny
 
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Old 12-06-07, 04:31 PM
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No electric

It is unlikely it will work, certainly not very efficiently & how are you going to control the heat?
 
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Old 12-06-07, 05:02 PM
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As long as it is a continuous rise from the boiler to the rads and a continuous drop coming back it will definitely work. That's easier said than done because how well depends on drops vs laterals, piping diameters and a whole bunch of calculations that have gone to the grave with the dead men of yore.

As Grady says, the tough part will be how to control the heat. You may be able to use a mixing valve, TRV and TV of some some to limit heat going into the house, but where will it go instead? You should use an antifreeze designed for heating systems, not the automotive stuff. I'm not sure how long it would last in an open system because of all the oxygen that will be in the water.
 
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Old 12-06-07, 05:07 PM
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I think a definition of 'work' is in order here.

I say that you may get some gravity FLOW, but I don't think you'll get satisfactory results... The difference in elevation is probably not enough to get adequate flow...
 
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Old 12-06-07, 06:05 PM
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Everything I know about gravity hot water systems I learned here:

http://www.heatinghelp.com/heating_howcome1.cfm

Like Who said, a lot of this knowledge died a long time ago. Terrific that some of it is preserved here.
 
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Old 03-17-11, 08:30 AM
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Yup. But call it thermal siphon.

I heat the floor in my house with a 2500 watt electric element from a water heater. The heating unit is above the floor. For an effective thermal siphon system think pull not push. I am pulling hot water through 3 zones of 1/2" poly pipe; each 100' in length.
 
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Old 03-17-11, 09:22 AM
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Hi TinKan, welcome to the forums.

I only want to point out that the post which you replied to is over three years old. Please be aware that there really isn't much point in responding to a topic that has long since been forgotten about.
 
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