# BTU output - basebd. vs. cast iron rad.



## leeeallen (Nov 22, 2009)

Can anyone tell me which senario will deliver more BTUs? A 12 foot section of  forced hot water baseboard or an 8 fin cast iron radiator measuring 36 H x 20 W x 8" deep?


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## kenny chaos (Nov 22, 2009)

MEHEAT said:
			
		

> Can anyone tell me which senario will deliver more BTUs? A 12 foot section of  forced hot water baseboard or an 8 fin cast iron radiator measuring 36 H x 20 W x 8" deep?





Figure about 7200btus. for the 12 footer.
Now look at the end of the cast iron
and count the number of vertical tubes; 1, 2, 3, 4, 5, 6, 7?
Gimme that # and I'll tell ya.


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## leeeallen (Nov 23, 2009)

from the end , there are 3


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## kenny chaos (Nov 23, 2009)

3 tube,36" high = 3.50 sq. ft. of EDR

3.50 sq. ft. of EDR x 8 sections(fins?) = 28 sq. ft. of EDR

28 sq. ft. of EDR x 170 BTU/Hr.(hot water, not steam)= 4760


  -  4760 btu's  -


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## btuser (Nov 24, 2009)

One thing I did learn about cast iron radiators was the ornate castings don't only improve the looks, they also increase the surface area of the radiator, giving more places for heat to dissapate.


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## in hot water (Nov 24, 2009)

the heat transfer differs a bit.  With a cast iron radiator heat travels as radiant (as long as you can see it, like the sun)  convection with the air currents moving up through the sections, and conduction if you touch or sit on it.

With fin tube baseboard it is mainly convection, or forced convection if you put a fan below the fins.

I like the warmth from old cast iron better, like a bright sun shinning on you.  It warms objects that are in it's line of view, like a radiant floor or ceiling.  And a nice place to warm clothes.

 hr


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## powerspec (Nov 24, 2009)

This web site will give you the answer you are looking for http://www.colonialsupply.com/resources/radiator.htm


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## chuck172 (Nov 24, 2009)

Would old cast iron radiators qualify as low temp. heat emitters like the modern europeon panel radiators?
When used in hydronic heat, how well will they do with 140* hot water?


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## Jeff S (Nov 24, 2009)

Yes ,you can use them at lower temps.Using the chart from colonial supply 140* would be 90 BTU per EDR.Plugging that into our example radiator of 28 EDR would give an output of 2520 BTU at 140* water.

For easy reference
120* = 50 BTU per EDR
145* = 100 BTU per EDR
170* = 150 BTU per EDR
The chart is very linear ,you can add or subtract 2 BTU per EDR for each degree of water temperature.

When I installed radiators through my entire house this year I purposely tried to oversize them so at design load of 0* outside and 70* inside that I would only need 145* water,of course when your dealing with used radiators your size of selection is limited.In my case of 30000 BTU I would need 300 EDR but only ended up with 268 EDR which would require the radiators to need an output of 111 BTU per EDR or approximately 150* water.

Yesterday when the outside temps were in the 50* + range I was maintaining my house temperature of 70* using 100* water.That's one of the benefits of water storage.


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## chuck172 (Nov 24, 2009)

That's very interesting, I really believe that low temp emitters are very important to the overall efficiency of our heating systems. Seems like most people including me have the standard fintube radiation. Radiant heat is the way!!


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