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Vacuum Condensate Systems

David Tetreau
David Tetreau Member Posts: 15
in THE MAIN WALL
What is the position of any knowledgeable people here; on using vacuum breakers at the terminal equipment (mostly radiators, some steam coils) when the condensate system is a vacuum return system? The system steam pressure is 5 psi and the vacuum system operates at about 3" Hg at the vacuum pump.

Many other mechanical engineers I have spoken to inside and outside the company are 180 degrees out of phase with each other. Some say never, to allow the vacuum to be broken allows air into the coil or radiator and leads to carbonic acid buildup in the condensate piping. Some say it is OK.

An additional question is; When condensate receivers/pumps are used to lift condensate from AHU coils up to the condensate return lines (under vacuum), can these coils use vacuum breakers and can the receiver tank be vented?

Thanks for any response.

Comments

  • EBEBRATT_4
    EBEBRATT_4 Member Posts: 10


    If you can find the NASH Company they used to be in South Norwalk Ct, but have moved-- they have an excellent small book on vacuum systems-they may be in Ohio--i dont remember and cant put my fingers on my book right now.

    In any event I would say not to put vacuum breakers on the coils or radiation. The steam pressure is high and the return line pressure is low-just what you want-a vacuum system is supposed to move the condensate quickly as compared to a standard steam system they usually use smaller piping. Breaking the vacuum with vacuum breakers will hinder the ability of your vacuum pump to keep a vacuum on the return line-you will be redesigning an existing system and have real problems. As for condensate receivers connected to a vacuum system they can be vented when lifting condensate to an overhead return. Make sure you have a large enough "water seal" that the vacuum will not pull out on the pump discharge. The coils connected to these receivers can and should have vacuum breakers(especially when handeling outside air). The water seal on the pump discharge seperates the "standard system" from the "vacuum system"

    But try NASH they can explain it better than I can.
  • David Tetreau
    David Tetreau Member Posts: 15
    Vacuum return systems

    Thanks for the help - any other help is appreciated as well as horror stories and do's/dont's re the subject.
  • David Tetreau
    David Tetreau Member Posts: 15
    The Nash Company

    This may the company you are talking about:

    nash_elmo
    1. http://www.nash-elmo.com
    Trumbull, Connecticut

    Nash_Elmo Industries was formed by the merger of two leading manufacturers of industrial vacuum pumps and compressors: The Nash Engineering Company, a family-owned company based in Trumbull, CT, and Elmo Vacuum Technology GmbH, a division of Siemens AG based in Nuremberg, Germany. The transaction creates a global organization with more than 200 years of combined operating history. The company’s products include liquid ring vacuum pumps, side channel blowers, and a variety of other pumps, compressors, and industrial equipment.
  • EBEBRATT_4
    EBEBRATT_4 Member Posts: 10


    Actually I just found them on this website. Click on "virtual trade show" and follow it down to "nash Jennings Condensate pumps" If I could find that book of theirs-it's probably what you need. Will look tommorow and reply.

    Hope this helps
    Ed
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,474


    Found my Nash book it is "Bulletin #H-1031" dated 12/14/92 and is a reprintof the original 1955 issue. The title is "Some Basic Principles of Steam Heating Systems" 14 pages long and explains the advantages of a vacuum system.

    Hope this helps
    Ed
  • David Tetreau
    David Tetreau Member Posts: 15
    Vacuum Condensate Systems

    Gee - the more you look, the more you find.

    What a surprise to find the boilers serving this system are actually rated to produce 15psig steam, but the controls are set to operate at about "3 to 4 psi" according to the maintenance people. Most days it hovers near 5 psi that I have witnessed. I have always heard bad things about operating boilers at any other pressure than design.

    The owner now wants us to install a PRV, operate the boilers at 15psi, and set the PRV to 2 psi, the original system design pressure.

    Any comments on what is going on here (other than lieing) and how we can reasonably run this system?
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