Unnecessary Condensate Return Pumps

SDSteam

Recently started working for a local university with a central plant LPS steam system. All of our main supply and return piping is in tunnels that are very accessible. At the plant we have a vacuum / condensate return pump that feeds our feed water tank. The condensate return main T's about 150 feet from the plant. One branch serves 4 buildings and the other serves 9. 2 buildings are served separately directly from the plant.

We currently don't use the vacuum pumps because of a combination of bad piping, failed steam traps and improper vents/vacuum breakers in various locations. I'm working on getting everything straightened out slowly and surely thanks to the knowledge I've gained from this site, Dan's books and anything and everything I've been able read or watch about LPS vacuum systems.


One major issue we have is that various condensate receiver/pumps in our system have vents that are open to atmosphere. I'm told that when they used to run the pump, it would pretty much just suck air through these vents and never pull more than 1" hg.


I now know how to properly pipe these receivers, but I'm trying to figure out why we even have them. There are only 3 buildings that have steam equipment that could not gravity feed back to the return main. In these 3 buildings, there are only a total of 2 air handler coils, 3 tube & shell heat exchangers and maybe 5 steam main drip traps that could not gravity feed to the main and would require pumping.

I know that 4 of the buildings with seemingly unnecessary pumps pre-dated the existing heating plant and tunnels and used to pump their condensate to a common pit that was then pumped back to the former heating plant. When the tunnel was connected to the buildings, the pump was simply piped into the new return main in the tunnel. In one of the buildings, the pump discharge literally goes up 7 feet, over 6 feet and back down 7 feet through the floor and into a crawl space that leads to the tunnel. In another, the condensate enters and discharges at the exact same height.... There's absolutely no reason that I can see for these pumps and most of the others in our system to exist.

Instead of properly re-piping the existing receiver/pumps, is there any reason I shouldn't just get rid of all of the unnecessary units? I haven't read anything that gives any reason to have a receiver where one isn't necessary. In fact, everything I've read says to avoid them if at all possible. Am I missing something? Isn't gravity the preferred method of condensate removal?

Pumpguy

To prevent air leakage into the condensate pump receivers, you will need to fit a check valve to the tank's vent pipe. This will allow any positive pressure to vent off to atmosphere, and still allow you to pull a vacuum on the return lines feeding this receiver.

In order for the condensate to return to the main plant without being pumped back, it will need to flow downhill by gravity.

Another possibility might be for the condensate to flow downhill to a central low point, and then use vacuum to lift up to main plant.

It's hard for me to envision how you would get condensate from campus outbuildings back to central plant without pumps of some sort.

Typical campus arrangements I see use 30 or 40 psi discharge pressure to get condensate back to main plant. I also see individual vacuum condensate pump packages in each building. This allows supply steam pressure to be reduced @ each building to 1-2 psi.

Depending on construction of existing condensate return pump packages, it is possible to add a separate vacuum pump to these units.

We have done this type of conversion several times with good success.