Three Pipes for a Two-Pipe Vented System?

FlyingScotsman

In the recent NY Times article, you can see the radiator, front and center, with two manual valves and an air vent.

From my understanding, (Thank you Mr. Holohan) this is effectively 'one pipe with drains'; there's a differential in sizing between the steam supply and the steam flooded condensate return, but it's just a basic improvement on one-pipe, allowing a condensate-free supply main.

So what's the third skinny pipe?
Air vent from the top of the main riser, coming back down?

cgdelzell

vacuum air vent, may just go to flue piping breaching to draw air out of the system faster. May also go to a vacuum pump.

Steamhead

Otherwise known as the Paul system. Follow those pipes into the basement and I'll bet they connect near the boiler. If you're lucky, you may find some of the old Paul equipment down there.

FlyingScotsman

Steamhead you're amazing. What's the internet equivalent of buying someone a beer?

This is an air removal system...a vacuum system... for use with exhaust steam, and patented 1896.

Awesome!

Steamhead

Get a copy of Dan's book "The Lost Art of Steam Heating" and you'll find the Paul system in chapter 15.

So how does it work now? Traps on the radiators and vacuum on the return lines?

FlyingScotsman

How is unclear.
Traps on the radiators, check.
Thermostatic control valves also.
Can't see any air vent connections on the radiators.

Photo: Air riser and steam supply riser both have F&Ts and connect to the same condensate return pipe that is just gravity - goes to a atmospherically vented receiver tank with pumps.

Condensate return goes to its own return pipe that is connected to a vacuum header, but the vacuum pump is off.

Has someone come in here and not figured this out properly, or is this a reasonable approach?

Steamhead

Interesting. Is anything else connected to the small pipe on the floors above?

FlyingScotsman

That's something to check out. Will report back.

And will definitely buy Dan's book.

FlyingScotsman

By the look of the patent, the air/vacuum pipe might connect to the condensate return in the chase, so maybe it's not doing any harm, but it's not doing any good, either, especially if that condensate pump ever backs up.