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Member Posts: 50
edited December 2014
Hello,

I am just looking for confirmation that I am calculating EDR correctly. Does the attached radiator have an EDR of 29.26? It is 20 inches tall, and here is the math I used: 11 (sections) x 2.66 (Sq ft/Section).

Thank you!

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It's 2.66x11=29.26sq ft EDR
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Ok, perfect. And then I multiply that number by 240 to get the BTUh, is that right?
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Yes, but if you are looking to replace a boiler, you should base that on the sq ft of steam the boiler makes, NOT its btus. The boiler manufacturer already includes the pick-up factor in their rating. compare apples to apples.
Two-pipe Trane vaporvacuum system; 1466 edr
Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
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I looked it up in Dan's EDR book and a six tube, 11 section, 20" tall radiator is 33 sq. ft.
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vaporvac said:

Yes, but if you are looking to replace a boiler, you should base that on the sq ft of steam the boiler makes, NOT its btus. The boiler manufacturer already includes the pick-up factor in their rating. compare apples to apples.

Thanks Vaporvac, but not looking to replace a boiler. Looking to confirm I need a larger radiator in my kitchen.
Fred said:

I looked it up in Dan's EDR book and a six tube, 11 section, 20" tall radiator is 33 sq. ft.

Thanks Fred - 33 sq ft, or 33 EDR?
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edited December 2014
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The sq. ft. is of EDR. 33 sq. ft. of EDR = 7920 BTU's per hour
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edited December 2014
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Oh, perfect, and good to know. Last question then - is it normal in this day and age to have radiators that significantly exceed a rooms need, or am I doing something wrong in my calculation?

For example, I have another room thats radiators BTUh I've calculated to be at 10,800 and this site is stating I require only 4,686!

http://www.bestheating.com/btu-calculator
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Not unusual. Back when these radiator were installed, with coal fueled boilers, they just simmered all day. Most every house with steam heat has larger radiators than needed but they work well as long as the boiler is matched well to the capacity of the total EDR. On most days those radiators won't get hot all the way across so you really aren't pumping more heat into those rooms than needed and you have the flexibility of slowing them down even more with the radiator vents.
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mcvetyty said:

Oh, perfect, and good to know. Last question then - is it normal in this day and age to have radiators that significantly exceed a rooms need, or am I doing something wrong in my calculation?

For example, I have another room thats radiators BTUh I've calculated to be at 10,800 and this site is stating I require only 4,686!

http://www.bestheating.com/btu-calculator

Definitely, when these rads were installed they were sized on worst case scenario 0 degrees and the windows wide open. So yes a lot of these old rads are significantly over size. Venting the air slowly will help the room from overheating.
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The vent on that radiator seems a bit too high. I would place it in the middle port that looks like it needs to be tapped.