Proper HW Radiator Piping

Jeff Guttman

Mike:

Thanks for your help!!!

Jeff Guttman

Proper HW Radiator Piping

I received a used steam radiator from a fellow employee who was renovating his home. I plan to use it in the hot water heating system at my house, as an additional source of heat in the "always chilly" living room.

It's a small American Radiator Co. unit, about 6 inches wide, 21 inches long, and about 27 inches high. It appears to have all of the sections nippled together across both the bottom and the top. As a steam unit, it was piped with the steam inlet on the top of the one side and the steam outlet on the bottom of the same side.

Now the question. How do I pipe it for hot water use?

My existing radiators (installed around 1933) are piped with the inlets on the bottom of one side, and the outlets on the bottom of the other side. Doesn't that tend to allow the water to "short circuit" across the bottom of the radiator? They seem to work perfectly, but I wonder if there is some sort of baffle inside that diverts the water towards the top the unit.

I was pondering the idea of supplying the new unit on the bottom of one side and returning on the top of the opposite side. I was hoping to eliminate this possible short circuiting and give the water an equal distance to travel through all the tubes. Am I really gaining anything by doing this, or should I just pipe it the same way the existing ones are piped?

Any advice you could give would be greatly appreciated.

Mike T., Swampeast MO

Piping hot water rad

Bottom-bottom connections usually work OK because the internal passages are so big that the water tends to slow and move through the rad by convection. A really big circulator can make it short circuit through the bottom. You'll know this is the case if the rad actually gets hotter when you close the valve half way or so.

Top supply-bottom return connections are highly acceptable for hot water use. Not only does it put the valve up higher where it's more convenient to use, but it sets up a natural "flow struggle" in the rad and given sufficient BTUs, it's certain to get hot top-to-bottom, side-to-side.

Steamhead

Either way will work

but a possible pitfall when connecting the supply pipe to the top of a radiator, is that air accumulation can stop the flow of water. On a bottom-connected radiator with some air accumulated in it, the water will still flow although the rad won't heat well.

Of course, if you have a good air separator and are "Pumping Away", you won't have to worry about air accumulating in your radiators (ask me how I know that)!

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