How to Calculate BTUs for a pipe

Laszlo

I have a steam system. Want to make a radiator for the bedroom; standard sizes don't fit the space. Need about 7,900 BTUs. How do I calculate the BTUs for black pipe or copper pipe? My local plumbing supplier doesn't know.

kevin coppinger_4

you say...

std. sizes dont fit the space? what size would fit? Runtal makes steam rads tofit in tight spaces if that helps you....kpc try www.steamradiators.com

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Mike T., Swampeast MO

A \"Pipe Coil\" Radiator...

May be very difficult to make, but here are the numbers.

Using black pipe you will get about 300 btu/hr per actual square foot of pipe surface area under "standard" steam and room air conditions. Such radiators are noted for very high output ability--even higher than single column standing rads.

1" black pipe (the smallest diameter ever mentioned for pipe coil radiators) have one square foot per 4¼ lineal foot of pipe. For larger pipe, merely compute the square footage based on outside diameter.

So, for 7,900 btu you would need about 26 1/3' of pipe.

Note however that this is NOT for a simple 26 1/3' long horizontal run! While my steam knowledge is slight, I believe such would have terrible condensate return problems. The pipes are arranged in rows (6 seems common) in a sideways "L" with the pipes about 4" apart. The dead men had end manifolds available and I seriously doubt that they are still made.

Even in the days of the dead men, these type of radiators were considered expensive and labor-intensive. L-R threading or lots of unions. Difficult to assemble with extreme accuracy required.

You might be able to fabricate similar using fittings, bushings, etc., but I would prepare for extreme frustration. A vertical bank of pipes can be used as well, but output probably won't be quite as high as when the majority is horizontal. I'd drop the standard output estimate to around 180 btu/hr per square foot of surface area.

DanHolohan

It's here:

Heat loss through bare pipe

It pays to wander off the Wall.

Mike T., Swampeast MO

ARGGH! Terrible Math Error in Above!

That's NOT 26.3 lineal feet of pipe, it's 26.3 SQUARE FEET.

With 1" black that's about 112' of pipe!!!

I certainly won't doubt Dan the Man, but I suspect that rating showing about 125 btu/hr per lineal foot of 1" pipe under standard conditions is based on a properly sized pipe that feeds a radiator or other load at standard conditions.

Unless I made another stupid error (and I did my best to check) that would give about 525 btu/hr per square foot of surface area. Seems to show why steam pipes in your basement really need to be insulated!