Two pipe system >> no traps or vacum pump

Tom_24

Hello Steam gurus.
I just took over a 13 story 1930s building (I am a property manager) that has two pipe system, with no traps and no vacuum pump. The main problem that I have is that most of my air vents are spitting water. I think they should close as soon as the vent reaches certain temperature. What is worst is that one of the lines (last one on the system) is being unsatisfied, in other words the upper apartments will not get steam because the cycle is over. I am about the change all the air vents. Any other suggestions?

Al Letellier

vents

Certainly a good place to start, but not knowing exactly what you have for system makes it tough to speculate. There has to be some device to get the condensate back into the boiler. Have a pro check out your system, it will save you alot of headaches.

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Steamhead

Tell us more

Are there vents on the radiators? Are there shutoffs on the returns as well as the supplies to the radiators? Is there any strange-looking hardware in the piping near the boiler?

Generally speaking, 2-pipe steam systems don't use radiator vents. The exception is the "2-pipe air-vent system" which uses shutoff valves on the radiator return connections, as well as vents on each radiator. But by the 1930s, this type of system had been superseded by Vapor.

If there's just an elbow on the radiator return connection, it's probably an Orifice Vapor system. Or there may be a check valve or water seal in the elbow, or in the bushing that the elbow screws into.

Post some pics if you can!

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john_24

any ideas on where I can get information

on the 2 pipe air vent system. we just got an account that fits your description. There are 2 pipes with valves on each radiator and an air vent as well. as far as I can tell there are no traps in the system at all. I have to repipe the boiler as the near boiler piping is a mess and we have at least 3 radiators that are cracked and need to be replaced. too many hands have been playing with this system and I would like to make sure that we do it right. I was going to research this system as its new to me but if you could point me in the right direction it would be appreciated.
Thanks
John

Steamhead

It's actually pretty simple

You install the boiler the same as on any other system. All your "dimensions" (lowest steam-carrying pipe above the waterline) are "A", not "B", since there's nothing to stop the leftover steam pressure.

Vent your steam mains quickly. Oversizing the main vents a bit will help since you can keep the pressure very low.

Do not install vents on any return lines. One of the problems with this type of system is steam getting into the returns. This is to be avoided since it can cause banging.

Often, the returns on these systems were piped so they join together above the boiler waterline. With this configuration, it's way too easy for steam to rush thru the return lines from one radiator to the next. Use a Vaporstat instead of a Pressuretrol to keep the pressure below 1 PSI- this will minimize the problem.

Obviously, if all the radiator returns drop into a wet return before joining together, the above problem doesn't exist. If they did originally but the new boiler's waterline is too low to submerge these lines, build a False Water Line to submerge them again, or set the boiler up on a pedestal or blocks.

When replacing radiators, you can use either steam-only radiators or ones that will work for hot-water or steam. Connect them exactly as the originals- with two shutoffs and an air vent.

This system is covered in Dan's book "The Lost Art of Steam Heating", available on the Books and More page of this site.

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john_24

thank you very much