Radiator rating

Jeffrey Eichenwald

I have a building with cast iron radiators by American Radiator.  See attached photos.  They are all piped as a two pipe steam radiator but all have an air vent on them.  Any info would be greatly appreciated.

Steamhead

What is on the rad return connection?

an ordinary rad valve? 

Jeffrey Eichenwald

Radiator info

Yes, it is a regular radiator valve.

JohnNY

2-Pipe, air vent system.

Jeff,

That's an odd one, but don't change it.

It's a 2-pipe, air vent system and it was installed in the early days of steam before thermostatic traps were invented.



Each radiator needs what we now know as a 1-pipe air vent and some steam will always make it into the return. It's designed to work that way.



Good luck with it.

Steamhead

John's right

it's 2-pipe air-vent.



The main difference between this system and the usual 2-pipe or Vapor system with traps/water seals/orifices, is that the return lines do not handle the air from the radiators. They only handle returning water. The air vents get rid of the air in the rads. Therefore you do NOT need- or want- to vent the return lines, as that will cause banging when the steam gets into them.



The steam mains should be well vented, as on any system, and the pressure kept as low as possible. Use a Vaporstat instead of a Pressuretrol to keep some knucklehead from jacking the pressure up. If the returns from the various rads are connected before they drop below the boiler's waterline, as they were on many systems, high pressure will push the steam into the returns, looking for an open air vent on a distant rad.



If you want to use TRVs on this system, use the type that replace the air vent, not the inlet valve.

Jeffrey Eichenwald

Radiator ratings

Guys,

While I appreciate all your comments, apparently no one read the title of my post-which was RADIATOR RATINGS!  I am well aware of the operation of a two pipe air vent system.  What I am looking for are the ACTUAL OUTPUT RATINGS OF THESE RADIATORS.  They are manufactured by American Radiator around the turn of the 20th century.  They look similar to the Roccoco type radiators but there are no two pipe type ones in any catalogue I can find.  Anyone have any output info on these radiators?

Jeff

nicholas bonham-carter

2-pipe rads

The edr will be the same as a conventional 1-pipe radiator.

I certainly echo steamhead's advice in saying the pressure should be "vaporstat-low".

Make sure the main venting is generous enough for the air to escape at a low 2 ounce back-pressure.--NBC

Steamhead

They look like American "National" radiators

you can find them in here:



http://www.heatinghelp.com/article/158/Radiators/1256/1897-American-Radiator-Company-catalog



The illustrations are a bit different from the examples you have, but the EDR would be the same. The tapping arrangement on yours is rare, but not unheard of, and it does not affect the rating.