# Using 1" black iron pipe as a hydronic radiator, how many feet of pipe would I need to heat a 500ft^3 room?

I guess industrial is hip these days. Or maybe it's just me. But I'm thinking of making a snaking heater/towel warmer for my bathroom remodel. How many feet would I need, and how is this calculated?

The room is 10x5. All the other walls on this floor are exactly half covered with radiant heaters. I'm not sure how many BTUs per foot that puts out, but I assume that's relevant to the question. By that, I'd think I need the equivalent of half of 15 feet of heaters? But that's more than I'd ever be able to fit into a bathroom anyways. Realistically there's about 7 feet of space along the one uninterrupted wall.

Other considerations that I wouldn't mind people chiming in on:

• Rust scale in heating lines?
• Don't worry, I know I'll need a dielectric union to prevent corrosion between copper and iron
• I might need to remove some heater from the other room to make up for less surface area in the bathroom. Not a problem, I wouldn't mind opening that wall.
• I suppose this is a burn risk if it's running at 180 degrees. Will the metal actually reach that temperature? Will I need to design some sort of heat cutoff redirect solenoid valve to make it function safely? Maybe I'll forget about towel warming and put a panel of tempered glass over it
• I'm thinking I'll wire-wheel it and season it with linseed oil on the outside to prevent it from making a mess of anything that touches it.
• If this is an all around silly idea, please let me know in a factual way, not speculation
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Are you attaching this to an existing hydronic heat system? If so, is this an older system (cast iron radiators) or a newer system (baseboard copper)? FWIW, I think most towel warmers are electric, as a typical bare heating pipe could get dangerously hot to the touch. – DA01 Apr 9 '14 at 22:01
Yes, existing and all copper. I did some research and found a lot of companies selling hydronic towel warmers/heaters. myson.co.uk, hudsonreed.com - It's peculiar, because I have the same concern you have. – kavisiegel Apr 10 '14 at 1:33
Here's a thought...run the HW through copper and then encase the copper in your iron pipes. – DA01 Apr 10 '14 at 1:36
heh, that's actually the general idea, but I'm going to use both... well, here's some drawings: i.imgur.com/DCdVlqG.jpg - If I wanted to do copper totally independent of the steel, I'd need to fill the steel with oil for heat transfer and I'd need to use pretty thin copper pipe. I'm not sure of pressure drops – kavisiegel Apr 10 '14 at 1:41
Possibly, but if it's baseboard heat already, most of the heat transference is via fins. For example, the metal covering to the baseboard heaters is usually pretty hot. So, one option would be to do essentially what you have, but add fins to the copper (instead of oil). You may need to make it a proper loop, though (So instead of an 'E' shape you may have to use an 'S' shape) – DA01 Apr 10 '14 at 2:18