[BLDG-SIM] eQUEST/economizer

[Sheila Sagerer]

Hi All-

What would happen if you forced economizer operation below 55F using the
cooling availability schedule set up as ON/OFF/Temp and designating cooling
during the spring, winter and fall as only available when OD temp is above
55F?  Would this then force the VAV system to increase airflow to the
required zones to satisfy cooling requirements (at the expense of increased
fan energy)?


Thanks,

Sheila Sagerer
Energy Engineer
Energy Opportunities, Inc
717-880-9069
Fax 717-291-9497



  -----Original Message-----
  From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Pat Bailey
  Sent: Wednesday, April 28, 2004 5:21 PM
  To: BLDG-SIM at GARD.COM
  Cc: postman at gard.com
  Subject: [BLDG-SIM] eQUEST/economizer


  David,

  We've run into this as well.  One issue that is relatively common with
simulated VAV systems is that the economizer operation and the VAV box
operation can be completely independent of each other, even if you don't
want them to be.  This may or might not be an issue in an actual system
depending on how the controls are configured.  Even if the design flow of
outside air is sufficient to cool a zone, the reduced flow at some level of
VAV turndown may not be sufficient.  For this reason, there are hours of the
year (typically cooler periods) when a constant volume unit may show less
simulated cooling energy.

  One solution to this is to schedule increased levels of outside air during
cooler months, perhaps in the morning.  The solution depends on when the
cooling load is not being met by outside air alone.

  You can also set the priorities of air flow and temperature reset.
Varying these will impact the trade off between fan energy and cooling
energy.

  Good luck.

  _______________________

  Pat Bailey, P.E.
  Principal
  GeoPraxis, Inc
  205 Keller Street
  Petaluma, CA 94952

  www.geopraxis.com
  707.766.7010 (v)
  707.766.7014 (f)

    -----Original Message-----
    From: postman at gard.com [mailto:]On Behalf Of David Lanceta
    Sent: Wednesday, April 28, 2004 11:35 AM
    To: BLDG-SIM at GARD.COM
    Subject: [BLDG-SIM] eQUEST/economizer


    Hi everybody!

    First of all, I would like to say thank you to everybody that have
helped me in the past, I used to send emails to everyone but I´m sure I´ve
forgotten some of them.

    I´m simulating an office building with eQUEST, and I´m trying to know
how much energy can be saved up.

    The HVAC system type is "Standard VAV with HW Reheat" for all the zones,
the cold deck reset is 55ºF. I´ve also set up a drybulb temperature
economizer, high limit 65ºF.

    I think that when the drybulb exterior temperature is below 55ºF there
should be free-cooling, but checking the temperature values this only
happens when it´s under 49ºF

    does anybody know why it could be?

    thanks
    =================================
    David Lanceta
    Área de Mecánica de Fluidos
    Centro Politécnico Superior
    Universidad de Zaragoza
    María de Luna 3, tel (0034)9761000 ext 5044
    50015 ZARAGOZA
    ESPAÑA

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