BTU Output

[Magneto]

Hey everyone I am a little stumped with an answer to a question someone has asked me, hoping someone on this forum could help me out.

So the basis of the question is surrounded by radiator btu output at different temperature systems.

For example if a radiators is producing a heat output of 5220 btu/h on a steam system running at 203 degree Fahrenheit, and a btu output of 2610 btu/h on a hydronic system running at 167 degrees, how do I base these numbers to tell me the different outputs that the radiator will deliver at different set system temperatures?

These radiators technical specifications are 617 btu per section for steam and 429 for hot water.

Any help would be greatly appreciated. I assume there is a formula for this, I just am not yet aware of it.

 

[Dana]

These ratings number presume 65F near the floor, and will be different in a much hotter or colder environment. But heat output rates of convectors & radiators are fairly linear with the temperature difference between the average water temp and 65F over a wide range of temperatures above 100F, with non-linearities creeping in below that. (The non-linarities of baseboard convectors shows up even at temps below 110F or 120F.)

Most radiators are specified for 180F water, and 215F steam and there will usually be correction tables for other temperature. But if you want the linear approximation without doing the arithmetic, take a look at the nomograph on page 2 of this document, or figure out the ratios looking at a manufacturer's correction tables, eg:

 

[Sponsor]

 

[hj]

HOW do you get "steam" ratings at 203 degrees water temperature? Unless it is a "vacuum" or vapor system.

 

[Jadnashua]

To have steam at 203-degrees F, you'd have to be at about 7Kft altitude or higher.

 

[Dana]

Those higher altitude systems exist in many parts of Colorado (such as Pb-ville.) In Stamford, CT, not so much.

It's possible the output rating was based on the radiator's temperature, not the temperature of the working fluid, though I've never read a radiaion spec that worked that way.