Vacuum in a Wacky One-pipe, Two-pipe system

VintageSteam507

We have a steam system in a large 1882 building in Philadelphia. The building originally had a ducted gravity heating system. We think the steam system was a retrofit put in anytime between about 1910 and 1950. The 40 year old boiler collapsed about 2013 and was replaced by a company that - we discovered - really didn't know what they were doing. After much trial and error, we got things working reasonably well after about a year. However, it was never working great and then it started leaking in 2022 (dismissed by the company who installed it), and then badly in 2023 . So, it was rebuilt-by a different contractor. The contractors who rebuilt it were smarter. They have also proposed installing a condensate return tank because the system has had a troublesome vacuum issue all along that seems to be impeding heating. Seems like an okay idea - although a $$K idea. However, I've been thinking back to the original engineering. Again, this is an odd one-pipe, two-pipe system (so, the supply and return are co-mingled). There are NO steam traps. We do have Gorton vents at the ends of the three main branches. We also have Gorton valves on the radiators. No Vacuum breakers on the mains. I'm starting to wonder if the original design intended to utilize vacuum. In that case, subsequent changes may have botched that. How do we start figuring out how to work best with the original intention of the engineering, and how best to work with it. Do we undo past modifications. Or, do we push further, install the condensate return tank, steam traps and vacuum breakers to convert it more fully. I have gone through Dan's first book and can't find a piping diagram that seems to be quite like ours!

mattmia2

What do you mean by one pipe two pipe? It sounds like one pipe from your description so far.

Are there vents on the radiators?

Are there returns on the radiators?

A condensate tank would be for a system where some of the radiators are below the boiler or otherwise can't drain by gravity to the boiler or with a large amount of condensate. Residential systems rarely need a condensate tank.

Pictures of the boiler and piping and especially a radiator or 2 will tell us a lot.

EBEBRATT-Ed

You need a steam expert to sort through this.

I don't know who is in PA but you have several good people not that far away. In NJ you have @EzzyT , @clammy , @JohnNY and @Steamhead in Maryland.

Some of these consult if they don't work in your state and could maybe work with your existing contractor.

If the system never had a condensate pump why would it need one now?

I am not against them if needed but if you need something a boiler feed tank is a better choice.

Also check find a contractor on this site.