sizing charts for cast radiators BTU values

See this book:

<A href=http://www.heatinghelp.com/shopcart/product.cfm?category=2-59>EDR by Dan Holohan</A> Some sample pages are available for viewing and you can always buy...

Note that radiators are rated by EDR (equivalence of direct radition) NOT output! EDR allows comparison among rads of different design/manufacturer.

For output in a hot water system you MUST know the average water temperature available to the radiator.

If you're making modifications to an existing system, ASSUME NOTHING! To avoid nightmarish balance problems that require extensive and expensive piping/control changes to correct you MUST assess the current system. You need a room-by-room heat loss calculation. Then estimate the average radiator temp required in each space to meet this loss. Then size any new or modified radiator similarly.

A <I>very</I> common mistake/problem reported here is sizing new radiation in old hot water systems using the "standard" output at 180° average water temperature. In many cases the average water temperature in the existing radiation will never approach this level and your new radiation will be terribly undersized.