EDR

Alan(CaliforniaRadiant)Forbes

Am I right when I use 230 BTU's per square foot when sizing steam radiators?

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Unknown

240

for steam, less for hot water.

Noel

Mike T., Swampeast MO

Most references I find (including Dan's) state 240 btu/hr per sqft EDR (assuming 1psi steam @ 215° in a 70° room).

Alan(CaliforniaRadiant)Forbes

Right on

Thank's guys. This is for a house in SF. They want to change out some of the radiators and I want to get the sizing right.

Best wishes,

Alan

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Mike T., Swampeast MO

A STRANGE thing

about some EDR tables, the ones that show a 10 btu/hr increase in output for each 5° increase in temperature...i.e. 110 btu @ 150°

At 95° (following that progression) the radiator is putting out ZERO btu/hr!!!!

Simple math: 95° is (11 * 5) or 55° lower than 150°.

11 "increments" times 10 = 110. 110 - 110 = 0 btu/hr @ 95°

IMPOSSIBLE!!!!!

Some of the radiators in my house heat the space to 70° when 8° outside (design temp) with a surface temperature LESS than 95°!!!!! This IS verified, I promise.

By using this formula I was able to quite accurately predict the surface temperature of a radiator (measured top, center) based on outside temperature:

Rad Output = (surface temp - room temp) * 1.5 * sqft EDR. This DOES NOT THOUGH have a 1psi STEAM rad putting out 240 btu/hr/sqftEDR!

I really believe some tables have an error that comes mainly from a delta-t error regarding water vs. steam!!!!!!