Copper pipe radiator design

gattu_marrudu · November 19

Hello there,

I have a small half bathroom adjacent to my kitchen. The bathroom is unheated, and its door is normally closed, so it gets pretty cold in there. I have a single-pipe, gravity steam system with a slightly over-fired furnace, so adding a radiator in that bathroom would probably be beneficial to the whole system. The bathroom is right above the end of the main steam pipe, so it should be a very short run to get there.

The bathroom is pretty tight, so I can go with a baseboard, but I also thought about building a custom radiator with copper pipe and fittings.

Attached is a sketch of what I am thinking. I haven't measured the radiating surface yet, so width and number of pipes is still TBD.

My main questions are:

First off, is this a good idea? Or is it a job for very experienced heating technicians?

Are there any obvious flaws in my design (leaving aside proportions)?

Where should the valve placed? Some radiators I see have it about halfway, some 1/3 from the top.

Is there an optimal diameter for the pipes, so they are small enough to give me a good heating surface, but large enough to let the steam and condensate flow freely?

Thanks!

gattu_marrudu · November 19

Come to think about it, why copper if I can use black pipe…

EBEBRATT-Ed · November 19

I don't think copper would be a good choice because the expansion and contraction will cause it to eventually leak.

@gerry gill had a job years ago where he made a radiator out of a single piece of pipe mounted vertically in a small bathroom. It was pretty cool. He made his by welding, but it could be made with screwed pipe as well. I will overlook for the post

bburd · November 19

Probably the simplest way to do this is to run a 1.5 or 2 inch steel pipe vertically in a corner of the bathroom, cap the top and drill and tap near the top for an air vent. Be sure the runout is pitched to drain back to the main and comes off the main at 45°.

This was the standard way of heating New York City apartment bathrooms in the heyday of steam.

Yes, there is such a thing as too much radiation, although most people like bathrooms on the warm side.You might want to calculate the heat loss of the bathroom to size the pipe. But you can always use a quality adjustable air vent to slow it down if necessary.

gattu_marrudu · November 19

I thought that horizontal pipes would distribute the heat more evenly across the room, but now I'd be curious to see the single pipe radiator.

I saw radiators in North Europe with a similar structure as what I drew, and they are also used as towel hangers. Probably water though, as steam would be too hot and ruin the fabric. Still, can't beat those guys at efficient design!

mattmia2 · November 19

The amount of solder in doing it in copper might not be an insignificant part of the total cost. Maybe you could find toe left hand thread nipples and part left hand fittings. or left right nipples and couplers.

mattmia2 · November 19

vertical pipes with a horizontal header at the bottom or at the top and bottom would deal with condensate better. you can use a horizontal header on the bottom with vertical capped pipes and a vent near the bottom of the pipe opposite the supply. the steam rises so it will fill the tubes sequentially and push the air out the far tube.

EBEBRATT-Ed · November 19

If it is 1 pipe steam you come up through the floor with 3/4 or 1" pipe. Put a valve on it then a nipple then a 3/4" or 1" x 2" reducing coupling with some 2" pipe in it with a cap on top with an air vent. Or a 2 x 1/2 coupling with a 1/2 x 1/4" bushing but tapping the cap would look better

gattu_marrudu · November 20

https://forum.heatinghelp.com/discussion/comment/1873033#Comment_1873033

A "comb" design sounds appealing as it would save me half of the tees and nipples. Are you sure the steam would be able to displace the air in the dead-end pipes, or would it rush toward the valve if it meets pressure? Has this system been built before?

I also like black pipe better than copper because it's thicker (especially with all those fittings) and creates a larger heat buffer, heating up and cooling down more slowly and uniformly during cycles.

ethicalpaul · November 20

It's hard to be sure, but with such short lengths of vertical pipe I think Matt is right that the steam would rise and displace the air lower where it will get carried/pushed to the vent.

Even if some air remains, the heat will conduct up to the cold pipes and result in a lot of good condensation of the steam as it gives up its heat to warm the pipe. I like the vertical pipe a little better for simplicity and space usage.

Regardless of what you build it will be easy to cool it off a little if you get too much heat off of it by such means as wrapping some of the exposed pipe with rope like the restaurants in NYC do it

mattmia2 · November 20

There certainly are steam only radiators that have the sections only connected at the bottom that work. Black iron is much better than copper because it has more mass and less thermal conductivity so it will heat and cool more slowly.

gattu_marrudu · November 20

Love the rope idea. I would save it for a place that's not near the toilet, where I'd avoid porous materials…

gattu_marrudu · November 20

Now to the EDR math — I remember one section in Dan's book mentioning direct pipe heating (which gave me this idea to begin with). I just checked and found that section, however it is for pipe coils, and the EDR is calculated per linear foot of coil length:

What is the coil length of a "single row" exactly? Is it the length of a single pipe wrapping around? Hence the ratings in the table must be divided by 2 for single pipe?

ethicalpaul · November 20

Just get an idea of your surface area using the circumference of your pipe times the length of it and you'll be fine. This ain't rocket science 😉

dabrakeman · November 21

=((PI()*Pipe OD * 12)/144)

Pipe OD is actual pipe OD in inches. Gets you sqft per lineal foot of that pipe.

Intplm. · November 22

Something like this would be best. They are/can be small to accommodate your small bathroom while heating the space adequately.

While building a piping arrangement for a small space can work. The piping can be laborious, unsightly, and may not heat the space as well as you want. This is one reason why radiators were invented.

Do an EDR as mentioned above and do the job correctly with no regrets. And as far as cost goes, it will be a little more. But not so much that you will have regrets. Heck, you could probably find a used radiator on the cheap or even free in good condition that will work for you.

Copper pipe radiator design

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