Do I need adjustable steam vents?

ebrinkm

I have a two pipe steam vent system (I haven't read We've Got Steam Heat yet, but I understand this is rare). Right now I have all adjustable steam vents (lowly USAV 884 models) that function with varying levels of success. So I've been thinking about replacing all the vents (I have 9 radiators) but I'm wondering if I need to get adjustable vents since I have two pipe steam - couldn't I just close/reduce flow by closing the supply line as a means of regulating flow and go with a non-adjustable vent? I understand you're not supposed to have the supply valves partially open on one pipe systems, but I haven't seen anyone say that definitively about two pipe.

Thanks. And if I should go the non-adjustable route, any recommendations? The Hoffman 1A / Ventrite #1 is sort of more than I want to spend if I'm going to replace all my vents which is part of why I'm asking. When do you go TRV?

Mark N

Normally with a 2 pipe steam system you don't need rad vents. Only if you have a 2 pipe air vent system do you need them. Do you have traps on the rads? Take some pictures. Do you have valves on both sides of the rads.

Jamie Hall

If you have a true two pipe air vent system -- valves on both sides of the radiators -- by far the best way to control it is with adjustable vents. So... if that's what you have, that's what you want.

ebrinkm

Attached is a photo of a typical radiator. Inlet valve, outlet valve, vent on the outlet side. Radiators vary in number of sections. All but two are this vintage.

Mark N

That looks to be a 2 pipe air vent system. Radiator vents are a personal preference. Buy a quality vent. I have no experience with the Hoffman's or Vent Rites.

Jamie Hall

Oh lovely! Those things are rare, but they work fine. And yes, that is the old two pipe steam with air vents -- and the control is by the vents, not the valves. The valves must be all the way open, or you can have problems with condensate building up and not draining.

Abracadabra

USAV vents are junk. The adjustable ones do not adjust anything from #3 setting i think and up.

ebrinkm

Thanks all. So what influence does the outlet valve have on the system? And presumably before the invention of the adjustable vents one did use the valves to regulate/balance the system? Partly just seems odd to have something that takes approximately six full turns to open all the way if off and on are really the only desired settings. One other question: were these 2 pipe vent systems low end, high end, novel? Just curious about the history of my house and why this system would have been selected (may be a topic for another post).

Dave in QCA

Two pipe vented systems were the preferred setup for early systems in Iowa. Probably other places too.
Terrace Hill National Historic Landmark, completed 1869, had a 2-pipe vented system (no longer in use). In Davenport, systems installed in the early 1880s were still being installed with he 2-pipe arrangement.

It seams the this method allowed the use of smaller supply piping and mains because the condensate was traveling in different pipes. While the supply valve can indeed be used to throttle the flow of steam to the radiator, 2 valves are necessary to completely shot off the steam because of the possibility of cross flow of steam between the outlets of radiators. This will not occur if every radiator has its own return connected to a wet return line that is low enough to form an effective water seal. Assuming that the piping is isolated, keep in mind that throttling the supply valve will effectively create a "B" dimension situation in a radiator that has no pressure because of the throttling, but where the return is still open. The B dimension amounts to 30" for every pound of pressure in the boiler. This is the height above the boiler water line that condensate will back up into the return piping. Of course, an adjustable vent is a good way to regulate a radiator on a 2-pipe system too.

Dave in QCA

Another story comes to mind; this one from Dan as told at one of his Steam Schools. It relates to a very expensive and exclusive apartment building in Manhattan, I believe it is the Dakota, the 1880s apartment building along the west side of Central Park, once the home of John Lennon.

Dan tells how the temperature control works via tenants calling the front desk and asking for more or less heat, the desk person sends up a heating person to adjust the valves on the radiator(s). With a smile, Dan explains that wealthy people have other people to turn their radiator valves. :-)