CALCULATING BTU OUTPUT OF CAST IRON RADIATORS WITH HOT WATER

K HAYNES

TRYING TO FIGURE OUT THE BTU OUTPUT OF MY CAST IRON RADIATORS. THEY ARE CURRENTLY USED WITH STEAM BUT IM GOING TO INSTALL A NEW BOILER AND USE THEM FOR HOT WATER. THEY MEASURE AS FOLLOWS 38" HIGH AND 5 TUBES PER SECTION . THE SYSTEM IS DESIGNED WITH A 180 DEGREE TEMP WHAT IS THE OUTPUT PER SECTION WITH THESE ANY HELP WILL BE GREATLY APPRECIATED

Jim Pompetti

Sections

How many section of radiator are there.A picture will help.

Unknown

The BTU

output for steam rads is 240 sq/ft.
HW in the same rads is another matter that depends on the water-temperature.
This can only be determined by a complete HL calculation.
180 is a pretty high design temp to use, the lower temp you can get away with, the more efficient the boiler you can use.
However, here`s some info from Burnham that should help determine what you have.

Dave

Supply House Rick

From Burnham's table

Compared to 215°F (0.9 PSI) steam at 240 BTU/SF

@ 180°F: 170 BTU/SF (71%)

@ 170°F: 150 BTU/SF (62%)

@ 160°F: 130 BTU/SF (54%)

@ 140°F: 90 BTU/SF (37%)

@ 120°F: 50 BTU/SF (21%)

For 38" 5 tube slenders assume 5 SF/section at 215°F Steam, so 3.5 SF/section at 180°. 3.1 @ 170°, & 2.7 @ 160°.

Full structure heat loss calc should tell you how low you can go in water temp. w/ the existing radiation.

Unknown

nbc

Is that not what I posted in PDF?,, sheesh.

Dave