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# unusual use for a cast iron radiator

Member Posts: 144
I'm planning on using some CI RADS for water to water heat Xs The rads would be installed in the bottom of a 2000 gal. insulated concrete tank. My question is does anybody know of a formula to figure the output of the radiators if I know the EDR for the radiators.The boiler is an old AM. RADIATOR redflash cast Ithink in 1934. Im firing it on wood and guessing output at 250-300K

• Member Posts: 6,708

good buddy.  The EDR of a radiator is "equivalent direct radiation" in square feet.  There are ratings around here somewhere for the BTU output of a radiator for various temperatures of hot water; for steam (or hot water at 212 F) it's 240 BTU per square foot.

However, that is a combination of convective heat transfer with air as the convecting medium and actual radiative heat transfer.  The rate of heat transfer to water will be very different, and will depend among other things on the temperatures (of course) of the water both inside and outside, and also to the velocity and turbulence in the water outside.

Sounds like an interesting experiment...
Jamie

Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
• Member Posts: 991
Sounds interesting

What is the system going to be used for, is the point to heat the 2000 gallons of water? Just curious, sounds interesting...

Anyway, why not just use a couple pumps and a 300K BTU plate exchanger?
• Member Posts: 144
edited March 2013
heat sink

The tank will be the main source for my radiant heat in a timberframe home I'm building for myself. If iwere to use a flat plate I would have to buy 1, rads are free. Tank is under no pressure so pumping out of it could be a challenge.
• Member Posts: 144
heat sink

The tank will be the main source for my radiant heat in a timberframe home I'm building for myself
• Member Posts: 144
More explanation

The tank is just a heat battery the CI rads heat the water and there will be some type of HX near the top feeding a fairly standard system.At a 70 degree differencial I can storeabout 1300K BTUs. Hopefully I can get my load down to 30-40 K. the whole idea is to fire the wood boiler hot and hard to get good combustion.
• Member Posts: 144
More explanation

The tank is just a heat battery the CI rads heat the water and there will be some type of HX near the top feeding a fairly standard system.At a 70 degree differencial I can storeabout 1300K BTUs. Hopefully I can get my load down to 30-40 K. the whole idea is to fire the wood boiler hot and hard to get good combustion.
• Member Posts: 144
More explanation

The tank is just a heat battery the CI rads heat the water and there will be some type of HX near the top feeding a fairly standard system.At a 70 degree differencial I can storeabout 1300K BTUs. Hopefully I can get my load down to 30-40 K. the whole idea is to fire the wood boiler hot and hard to get good combustion.
• Member Posts: 7,356
that's the right approach

Optimal tank sizing varies a bit with species, moisture content, and combustion technology, but is definitely worth the time to get right.
• Member Posts: 891
edited March 2013
Pumping will not necessarily be an issue

If the line never runs dry, and there's no reason it should, then it's no different than a pressurized system - the weight of water going down is the same as the weight of water going up, so there's no net work expended "lifting" the water. If it does run dry then the circulator needs to be able to lift water from the top of the tank to the highest point in the loop.

Pressure in a pressurized system has no significant bearing on how much work a circulator has to do, since it acts equally in all directions. You might want to search for "hot water zone from steam boiler" as the issues will be the same.

Now... you're getting cast iron rads for free and I definitely understand the appeal of making something free work for you. You might, however, run into issues with corrosion, as the water in the storage tank is likely to have its supply of dissolved oxygen continually replenished. There's also the issue of heat transfer efficiency - this might not be the best way to get the most heat exchange area and the most turbulent flow, and those two are kings when it comes to heat transfer. But, as long as you don't invest too much money into making the free thing work, and you've got the luxury of being able to experiment, this could be a fun project to try to get work optimally.
• Member Posts: 991
edited March 2013
I would love to see some drawings and pics

I love designing wood boiler systems, used to do a lot of them but now most areas outlawed them so not as many going in...

I designed my fathers system with taco 1400 pumps {ebay \$70}, 80 plate exchangers {\$150 ebay}, a 115 gallon Heat-flo storage tanks {\$700}, a few valves -Mixing and diverting, some relays and aquastats... runs his radiant, indirect, and water air modines... The entire wood boiler portion only cost around \$2000 in materiels {not counting the boiler} and that was 2 of everything 2 tanks, 2 pumps 2 exchangers ect... the boiler had 2 1=1/4" sets of lines so we used them all...

I woujld glass bead the radiator surface for better transfer, but still don't know how well they will work, I would do a small test with one and see what kind of return temps you get compared to you supply temps, then you will know about how much heat they will let you suck out... If you go in 190 and come out 180 probably not a great method to use..
• Member Posts: 252

you can put as many as u want into the tank and it will be economical, compared to a large plate ex or 2000gal of mfrd. storage tanks. so this is going to be a concrete tank? where in the basement? r u worried about moisture/humidity, smell, excessive heat transfer to the air? i personally love the idea of having as much water storage as possible and heating it with a wood boiler a few times a week, it is part of my dream system!
• Member Posts: 45
wood boiler

I put in a wood boiler made by HS TARM several years ago and we used a large tank about 6 ft across with coils of copper tubing as the heat exchanger. The boiler could be fired once a week to heat the tank and then all week we used the tank to supply hot water to floor radiant heat , we even heated a large under house garage with concrete floors. It has worked very well and also is a combination oil boiler.
• Member Posts: 144
moisture

this section of the basement is under the garage, concrete slab on top and 2 walls concrete. the tank is 8x8x6, 3 feet inthe floor ,3 feet above. There will be an insulated cover of some sort, only the hx tubes will have to penetrate the cover. The boiler and the tank set side by side,only about 15' of piping total. Two wall will be wood frame with moisture resitant drywall and and moisture barrier paint
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