Disconnecting AHU equipment from an existing low psig vacuum system

SteamTec

Would like to remove 2 AHU's from an existing vacuum system in a building with failing/rusting condensate pipe and failed steam traps. The main vacuum pump is 75 LF away from the AHU's down a tunnel in a large mechanical space The vacuum pump then pumps the condensate back to the boiler plant located across the street to a central power plant. Question: If I install a new electric set pump just for the 2 AHU's that are all tied together on the return side, where should I tie in the return from the electric set pump? Do I go back to the vacuum pump tank in the same building or directly to a main return going back to the boiler plant?

Thanks, Ron

Pumpguy

If you wish to have a vacuum on the returns that this new condensate pump unit handles the returns for, tie the tank's vent line into the vacuum return, not just to atmosphere.

See attached file for mechanical lifts. This should apply to your situation.

You have a choice of either piping the condensate pump's discharge into the vacuum return line, or direct back to the boiler or boiler feed tank. Just depends on weather you'd rather pump this condensate twice, or install a longer run of piping.

Henry

Vacuum pumps are there to either control the steam temperature or increase the speed of entering steam into the emitter. They are not for sucking condensate as many think.

jumper

Henry said:

Vacuum pumps are there to either control the steam temperature or increase the speed of entering steam into the emitter. They are not for sucking condensate as many think.

And hopefully gravity rather than pressure moves condensate through traps?

EBEBRATT-Ed

A vacuum system will move steam and condensate through a system using smaller pipe than a conventional system of the same capacity.

And yes, a vacuum system can lift condensate by using lift fittings when required to do so. But gravity return is free.