Gravity Baseboard Heat?

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Freddy
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Post Sun. Jun. 22, 2008 1:49 pm

On an oil boiler if the circulator pumps dies you can open the flow check and get some heat by gravity feed. It'll get you through a weekend until the parts stores open. I see some of the coal boiler people runt he aquastat a bit lower than an oil boiler, perhaps 140/170 instead of 160/180. I'm wondering.... If one were to use zone valves instead of pumps and had no flow check, or opened the flow check, do you think it would gravity enough to provide heat? It would be sweet if pumps weren't needed.
Orrington, Maine
Fred

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coalkirk
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Post Sun. Jun. 22, 2008 1:52 pm

I don't think so. You'd get a much better comfort level with a pump. Is it the cost of running the pump that concerns you or a possble electrical outage? The pumps are inexpensive to operate and with all the $$$ you'll be saving not using oil, the little bit of juice for the pump is a non-issue.
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gaw
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Post Sun. Jun. 22, 2008 3:59 pm

My guess is that you may get some heating, probably enough to keep from the house freezing but I think you will be damn glad to get the circulator repaired if that were to happen. I would even venture to guess that running a circulator pump saves on coal used and it is cheaper to use a pump than depend on gravity flow. I have no facts o figures, just pure speculation by me so I will waive my usual consulting fee :lol:
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Freddy
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Post Sun. Jun. 22, 2008 5:03 pm

I didn't know but maybe someone has done it. I was (still am) hoping that someone would (will) say "Ya! I do that, it works great!"

I'm thinking cost of running the pump. If the power goes out, the boiler won't run anyway. What I'm thinking is... when the thermostat calls for heat, the pump comes on and you have 180 degree water flow. It brings the rooms up to temp in a matter of minutes. With gravity feed, use a lower temp water, maybe 160 and it will flow slow & steady, keeping the temperature more even than if using a pump and hotter water. I now use gravity to resurcualte my domestic hot water to under my kitchen sink. The sink is 40 feet from the hot water tank, yet we have instant hot water. That's through half inch pipe. Both pipes are level. The bottom of the water heater is 7 feet below the floor under the sink. I think the gravity idea is worth a try. I use zone valves anyway. Honeywell, they draw only 7 watts. A pump draws 85 watts. I'll still have to pump the infloor, but that's only about 1/3 of the house.

I just went to see how much a pump draws & discovered I have a leak! Go figure, build a new house & 14 1/2 years later a fitting goes to leaking. I valved it off & will repair it when I install the Axeman Anderson.
Orrington, Maine
Fred

"If you can't say something nice, don't say anything at all".

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LsFarm
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Post Sun. Jun. 22, 2008 5:31 pm

A lot of older homes used gravity hot water,, but it won't do the job in cold weather.. the flow rate is too slow.. our baseboards and radiators are sized for being at and staying at 160-180*, with the slower flow rate with gravity only, the baseboards will be a lot cooler,, expecially the ones near the end of the zone's circulation..

Remember, the pump only runs when there is a call for heat,, not continously.. I have three full time running circulators with my system, sometimes four.. and three thermostaticly controled circulators.. my electic bill goes up in the summer from the one A/c unit in my Mom's apartment, and from the waterfall's water pump in the Pond..

I certainly wouldn't worry about the electrical use... however,, if you have a good chimney, with plenty of draft, if the power goes out,, with your AA, you can get some heat by proping a pipe against the inspection door, closing it so the chimney pulls some draft through the coal bed, and then opening your flow check, and zoned valves.. you will have some gravity flow.. enough to keep everything from freezing..

I've opened the zone valves and run a Natural gas boiler for over a week during a power outage, this was many years ago..

Greg L
Burning Pea/Buckwheat through an antique stoker [semi retired SSboiler],
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Yanche
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Post Sun. Jun. 22, 2008 6:10 pm

It would be possible, but not practical, to make a baseboard system gravity flow. Multiple baseboard units in each room would each have to be piped in parallel. Common supply and return piping to the boiler would have to be much larger. In addition considerable design effort would be needed to assure a balanced design, one that would deliver the correct amount of BTU's to each room. If you're serious I can recommend the design software (about $400-500) that would allow you to do it.
Yanche
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rberq
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Post Sun. Jun. 22, 2008 7:20 pm

My boiler up to a couple years ago was completely gravity feed to six radiators. As Yanche says, the pipes were larger -- 2 inch I.D. leaving the top of the boiler, 2 1/2 I.D. returning to the bottom. They were reduced to 1 inch I.D. once they got more than 10 or 15 feet from the boiler. Longest lateral distance was about 25 feet on each of two circuits. The system worked very well, much better than I would have guessed, and the heat was more uniform across all radiators than with the new boiler and pump system that replaced it. The first ten years we were in the house I didn't even realize it didn't have pumps, I thought they must just be inside the boiler cabinet or something weird like that.

Thinking of the pipe sizes, my guess is that most of the convective "push" to circulate the water came from the large quantity of water in the boiler and the large pipes closest to it. Return lines from the radiators were not lower, they ran right along the joists like the supply lines. The only place the pipes dropped down were right where they returned to the boiler.

The new cold-start boiler holds far less water than the old gravity system. I don't know which is closer to the water content of a coal boiler. So to feed baseboards with convection would probably suffer from smaller water volume to begin with, therefore less convective force. And the dynamics of moving the water through long horizontal baseboard tubes must be different from the dynamics inside a radiator, though I don't know just how significant that would be.
Simple answers for simple minds.

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Freddy
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Post Sun. Jun. 22, 2008 7:42 pm

It sure sounds like you are all correct. I'll plumb it properly but don't be surprised if I turn off the pump and see what happens come January. All my rooms do have more baseboard than neceaasary. Most of the back of my house overhangs the foundation by two feet. It was easiest to run baseboard the entire length. It was cheap back then & I was getting it at cost. I could have used "dummy" for a good part of it, but ran fins the whole way. Consequently I added extra to the front room so it would be balanced. That being so, I might have a head start in the convection direction. I know the cost for the electricty isn't huge, but if I can save a dime, I save a dime!
Orrington, Maine
Fred

"If you can't say something nice, don't say anything at all".


rberq
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Post Sun. Jun. 22, 2008 8:32 pm

Oh, 'fess up Fred, you're doing it for curiosity and fun and because it's a challenge, not just to save a dime!
Simple answers for simple minds.

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ceccil
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Post Sun. Jun. 22, 2008 10:34 pm

I would have to agree. Sounds like he likes a good challenge. He's also no different than most others here!! :D
Jeff
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Post Mon. Jun. 23, 2008 8:04 am

It will get cold in a hurry without the pump, I have opened the zone valves and lift checks in power failures several times. It will keep you from freezing, but won't really heat the house properly.
Nothing is impossible for people who don't have to do it themselves.

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Steve.N
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Post Mon. Jun. 23, 2008 8:51 am

I set up a gravity feed system in my living room that I use as an emergency dump zone for my wood boiler. I used large diameter pipe feeding the baseboard all sloped up at about 10 deg and the same size returning all sloped down for heat movement. I have a fail open valve for when the power goes off (happens a lot here) and havn't had a boiler vent in twenty years. The gravity section will keep the living room toasty with out the circulator but of course the rest of the house gets cold and supplies enough load to keep the boiler under control.
Life without oil heat is sweet !

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Freddy
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Post Mon. Jun. 23, 2008 11:40 am

"The gravity section will keep the living room toasty"

Ahhhhh HA! *smile*
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Fred

"If you can't say something nice, don't say anything at all".

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Steve.N
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Post Mon. Jun. 23, 2008 1:09 pm

Freddy,

Take a look at this page

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Life without oil heat is sweet !

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Yanche
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Post Mon. Jun. 23, 2008 1:32 pm

Nice information on the history of gravity heating. But how about how to design one from scratch today using modern baseboards and boilers? Is it truly a lost art?
Yanche
Alternate Heating Systems S-130
Stoker Boiler burning Anthracite Pea Coal


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