gravity feed storage

I'm thinking yes, but I don't know that it would be enough flow to keep things from overheating if there's a decent fire going.

Not sure that helped much.

You will get some thermosiphen if the pipe coming off your LU is at an upwards angle leading to your tank. I'm assuming a horizontal install. You need to pipe into the tank top with your Termovar. It doesn't sound like you will get the thermosiphen you need at full fire & a power outage though. I have 1 1/2" pipe with a very steep angle to the top of my vertical tank with my Lado LU & this doesn't transfer heat fast enough, Randy

8nrider said:

if the center of my 500 gallon storage tank

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Horizontal or vertical tank? What is vertical distance from top of boiler to top of tank?

8nrider said:

i have a 24'x 24' slab at the same elevation as the top of the tank to help with the dissapation it has 3/4 pex in it.

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8N, I don't see where that is going to thermosiphen well, out of your storage. Your slab may dissipate heat well, I think it will need pumped flow though, Randy

It would be feasible enough to at least run some numbers and get a better idea.

For mine I have 30 inches from top of boiler to top of storage plus about 36 inches of boiler with a vertical tank.

For worst case design I figured that storage would be fully charged to 180 degF (and therefore 180 degF return temperature) and the fire going full blast. Assuming a supply temperature of 220 degF I went and figured the weights of all the one-square-inch columns of water involved and came up with a three tenths of a psi of head or whatever and used that to figure the flow through the boiler, pipe, and elbows. I came up with a little over 4 gpm, which would be 80000 btu per hour on a good testing day, so I figured it was worth a try.

Got the system up and running and got storage up to 180 degF top to bottom with a good big fire and a nice deep layer of coals and cut the power. The supply temperature peaked out closer to 230 degF but it seemed to ride it out just fine. Once the draft fan was off things calmed down pretty well.

Good info Eliot-Thanks!

30 vertical inches from boiler supply to the top of the tank is pretty nice-(more than I will be able get with a horizontal 1000 gal tank)
Must have been a bit interesting killing power with tanks at 180 and a strong fire. Probably a must for all new installs to test overheat situations.

I have a couple of questions for you:

Does your boiler supply to storage enter the tank from the side(my guess) or does it drop into the tank from above with a 90? I would think avoiding any drop in the supply piping would critical in maximizing TS.

Which leads to my next Q:
Does your return piping drop continuously from storage to boiler return?

How bout you Randy?

Thanks guys,
Noah

8nrider said:

if it was at a full burn the loading unit would be satisfied and pulling from the storage. so flow would be established as a supply- return from storage??? i still can not see the pumping to instead of away w/ the loading unit?

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8N, I don't think the slab will thermosiphen well at all as its barely above the tank. You can move water into the tank as you will have some elevation there. I cannot run the temps EW can as my STS20 will open the built in cooling loop(exchanger) that is in my boiler,that opens at about 95C. One last thought, are you sure you are talking about the $600.00 Termovar LU? Randy

Floydian said:

Good info Eliot-Thanks!

30 vertical inches from boiler supply to the top of the tank is pretty nice-(more than I will be able get with a horizontal 1000 gal tank)
Must have been a bit interesting killing power with tanks at 180 and a strong fire. Probably a must for all new installs to test overheat situations.

I have a couple of questions for you:

Does your boiler supply to storage enter the tank from the side(my guess) or does it drop into the tank from above with a 90? I would think avoiding any drop in the supply piping would critical in maximizing TS.

Which leads to my next Q:
Does your return piping drop continuously from storage to boiler return?

How bout you Randy?

Thanks guys,
Noah

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Noah, Yes, my boiler output goes into the side of the vertical tank just below the head seam. The return is at a slight downward angle all the way to the Laddomat(return) Randy

Thanks Randy.

No rise from the Laddo to the boiler return?

Noah

Floydian said:

Thanks Randy.

No rise from the Laddo to the boiler return?

Noah

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The Laddo is right on the boiler return fitting & as the return port of the tank is above this, it's a slight downward pitch all the way, Randy

Floydian said:

30 vertical inches from boiler supply to the top of the tank is pretty nice-(more than I will be able get with a horizontal 1000 gal tank)

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Most of the old tractors don't have much more than a foot from top of block to top of radiator and they can dump 100,000 btu per hour with thermo siphoning easily enough. Of course they have 2.5" pipes that are only a couple feet long each way, and they have more like 50 or 60 degF deltaT to work with, but still it shows there's hope!

Does your boiler supply to storage enter the tank from the side(my guess) or does it drop into the tank from above with a 90? I would think avoiding any drop in the supply piping would critical in maximizing TS.

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With three tanks I have manifolds top and bottom that tee into the row of apexes of the tanks. Supply tees into the top manifold between the first two tanks and return tees into the bottom manifold between the second and third tank. There is of course no problem with going up over and back down, they don't call is siphoning for nothing and the top of the system can just as easily be above the tank as inside it.

Which leads to my next Q:
Does your return piping drop continuously from storage to boiler return?

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Actually it rises 1/8" per four feet towards the boiler because I set the tanks sloping down away from the boiler. This was just to get all the highpoints outside the insulated tank closet. As long as you're not trying to push a pile of cold water over a big hump, what's to stop the system from taking off and siphoning?

8nrider said:

yes it will be the $600 termover lu if bio heat ever recieves them i guess the way to find out if anything works is to do it. just looking for the simplest system. my wife is trying to get us away of being dependant on the generator during power outages.i guess yhere is always battery back up but gravity feed is way cool

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I agree, my entire heating loop is thermosiphen driven. I can turn my radiator valves all the way off & because they have the small weep hole to prevent freezing the thermosiphen will push enough water past them to heat my house at 45 degrees outside temp. I am surprised it works as well as it does, Randy