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  1. #1

    Air separator on chilled water lines

    OK, who's right? When our recently installed HVAC system was installed, the contractor question the engineer's location of the air separator. So, in reference to the chiller and the chilled water pump (supply and return, specifically), where is the accepted place to locate the air separator? And does it matter?

  2. #2
    Join Date
    Mar 2008
    Location
    NE Ohio
    Posts
    60
    I would put it at the highest point in the system.Thats the most likely place for air to get trapped.I would put a ball valve there so you can remove it and change it out when neccesary.And you can remove the air vent and bleed it manually if need be.

  3. #3
    We have air vents at all of the chilled water coils, as well as at the roof top chiller. I'm referring to the large air separator in the mechanical room with the chilled water pumps. Is that separator normally after the pump or before it?

  4. #4
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    A vortex air separator goes in the return line to the pump, just before the pump, with an auto-vent installed in the top.

  5. #5
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    593
    Quote Originally Posted by klove View Post
    A vortex air separator goes in the return line to the pump....
    I've never seen one any place else.
    http://www.bellgossett.com/literature/files/7161.pdf
    UA LU 562

  6. #6
    Thanks for your responses....I'll check it and get back tomorrow!

  7. #7
    OK, our system has 2 air handlers and 3 blower coils. The air separator is located at the end of the line on the supply line going into the air handler in the mechanical room with the pump. So it's almost on the return side of the pump. Is that location a problem? We're now out of warranty and the contractor had to add a few gallons of glycol to get the pressure up. A few weeks has passed and now the pressure on the return side of the pump is just a few pounds. When it goes to zero, the contractor says, the air vent can pull in air. Correct? We've now bought our own pump and will add glycol ourselves. If this situation continues, I guess an analysis of the condensate water is in order. There's no leaks in the piping that I can see. Any thoughts?

  8. #8
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    First: Could you tell us a little something about your qualifications in your profile. Chilled water systems are not a DIY gig.

    Second: The separator, by your description of placement, is not almost on the return to the pump - it is completely on the supply side.

    Third: If this is a vortex air separator and the engineer speced it to be installed where it's at now, I would request mfrs documentation from him showing that his recommended location is acceptable and will work satisfactorily for the intended purpose. It sounds like the separator has been installed on a branch line to an AHU, which would be assinine at the very best. You also need to get out your mechanical drawings and check the present location against what was called for.

    Fourth: If you have a glycol charged loop, you need to manually vent the air until it's gone while maintaining design system standing/return pressure, and leave the auto vents in the replacement parts cabinet.

  9. #9
    1) I'm merely the Facilities Director who has to answer to CFO in regards to HVAC service invoices. Everything that I learn, here and elsewhere, helps me explain things to her.
    2)Yes, you're right, the separator is on the supply side.
    3)In talking with the contractor today, when the separator was installed, the tech questioned its location and the engineer was consulted. The project manager then did call the manufacturer and was told that it didn't matter.
    4) I plan to close the valve at each air vent at each coil after I get the system up to pressure. As a non-profit, I like to do whatever I can, when I understand it.

  10. #10
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    Fair enough. Sounds like you've done everything that you can do to reasonably make sure that everyone has fulfilled their obligations. I don't necessarily have to agree with what the mfr says about the location of the device, but you may have to learn to live with it. The separator will work on the supply, just not near as well. I have a wife that is a CFO, so I understand that part, too.

    Close the shutoffs at the auto vents before you go home today. Glycol loves to cause the check balls in those things to hang open, and if you have no makeup, eventually your standing pressure drops to the point that you have 0 psig at the high spot, and you pull air in. Also, does your system have an expansion tank installed? If so, is it charged and set up correctly?

  11. #11
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    6,364
    DK

    Do a search for this manual:


    Honeywell engineering manual of Building Controls for Commercial Buildings.

    It’s a long down load 500+ pages but well worth it.

    What you’re looking for should be in it.

  12. #12
    Join Date
    Aug 2006
    Location
    Ohio
    Posts
    2,094
    Return line before the pump.

  13. #13
    Also, does your system have an expansion tank installed? If so, is it charged and set up correctly?
    We checked the air pressure on our TACO tank and it was 100psi !!!! So it was doing nothing for us. It was reused from our last system, but I don't know why the contractor had it there. We let out air and took it down to 20 psi. An engineer from a "losing bidder" paid us a free visit yesterday and he was quite helpful. He took our prints with him and is looking into a few things for us. Our most pressing problem is the mold in our new blower coil in the basement. If you recall a recent thread, the unit was not condensating. Our engineer had us change the CFMs from 2300 to 1000. That definitely got the condensation flowing and lowered the RH. We recently opened it up and there's more mold. Yesterday's engineer felt that we would have been better served with Freq. drive on the motor with the appropriate controls with it. It also has unaddressed problems in the Winter: With so many steam pipes down there and no chiller in the winter, the unit goes into economizer to cool the space. With all that dry outside air, a steam-to-steam humidifier and a relief damper, we're humidifying the outside. It's the main storage area for the museum and while we never had humidification there before, we still barely do! He's looking into that, as well.

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