[Equest-users] Demand Controlled Ventilation

[Greg Collins]

Rohini said, "the current version of calculating OA probably works for
Title 24?"

The answer is yes.  T24 requires 15 cfm per expected number of
occupants, with a minimum value of 0.15 cfm/sq-ft (this value depends on
occ type).  For a regular (non-DCV) system, your ventilation will be
constant and be based on the higher of the area and people based
calculations.  For a system with DCV, your ventilation amount will reset
from the aforementioned value down to the minimum area-based value.
eQuest is built for such.

Greg Collins
GLUMAC | (949) 833-8190

-----Original Message-----
From: R B [mailto:slv3sat at gmail.com] 
Sent: Wednesday, April 28, 2010 11:36 AM
To: Victor Yeung
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Demand Controlled Ventilation

What I had ended up doing was to use both the numbers /person and
/sqft. but the per person number is slightly higher than the actual
per person number based on the area of the zone and the cfm/area. You
can use a equation in this cell to get the equivalent number.
So during the occupied time, if the occupancy is zero any hour, the
/sqft value gets used, and rest of the time /person value multiplied
with the actual number of people gets used. It is not exactly what you
want but it is better than one or the other.
I hope the equest team include sthe ASHRAE ventilation calcs in their
next version - the current version of calculating OA probably works
for Title 24?
-Rohini

On 4/28/10, Victor Yeung <Victor at invirosystems.ca> wrote:
> James,
>
>
>
> This is from the eQuest help file:
>
>
> OA-FLOW/AREA
>
>
> This keyword allows the specification of a minimum zone outside air
(OA)
> flow rate per unit of zone floor area.  The use of OUTSIDE-AIR-FLOW
will
> over ride the value of this keyword.  The maximum of values resulting
> from OA-FLOW/AREA, OA-FLOW/PER, and OA-CHANGES will be used unless an
> over-ride value for OUTSIDE-AIR-FLOW is specified.
>
>  I've also tested this out by varying the OA-FLOW/PER in a model I've
> worked on.  The total energy consumption didn't change, which
suggested
> that my cfm/area rate was producing the larger cfm requirement and the
> program ignored my cfm/person rate.
>
>
>
> From: James Hansen [mailto:JHANSEN at ghtltd.com]
> Sent: April 28, 2010 2:08 PM
> To: Victor Yeung; Otto Schwieterman
> Cc: equest-users at lists.onebuilding.org
> Subject: RE: [Equest-users] Demand Controlled Ventilation
>
>
>
> "However, the way eQuest calculates min zone OA is by taking the
higher
> value of either OA-FLOW/PER or OA-FLOW/AREA, not the combine total.
To
> correctly model the OA requirement, I have to calculate the combine OA
> rate (i.e. {[cfm/per * max # of person] + [cfm/area * floor area] } /
> floor area) and input that value in OA-FLOW/AREA."
>
>
>
> Are you sure about that Victor?  Last time I checked, when I input 5
CFM
> / person and 0.06 CFM / square foot, the minimum zone OA was the SUM
of
> these two values.  In which case you can model DCV without having to
use
> that option in the system tab.  eQuest will automatically size the 5
CFM
> / person portion of the outside air based on the occupancy diversity.
> Am I wrong here?
>
>
>
> GHT Limited
> James Hansen, PE, LEED AP
>
> Senior Associate
>
> 1010 N. Glebe Rd, Suite 200
>
> Arlington, VA  22201-4749
>
> 703-338-5754 (Cell)
>
> 703-243-1200 (Office)
>
> 703-276-1376 (Fax)
>
> www.ghtltd.com <http://www.ghtltd.com/>
>
>
>
>
>
>
>
> From: Victor Yeung [mailto:Victor at invirosystems.ca]
> Sent: Wednesday, April 28, 2010 12:30 PM
> To: Bishop, Bill; Rob Hudson
> Cc: equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] Demand Controlled Ventilation
>
>
>
> Hello all,
>
>
>
> I also have a similar question related to minimum OA settings for DCV,
> particularly with OA-FLOW/PER and OA-FLOW/AREA.  Say I am using ASHRAE
> 62.1 for my OA rates, there are minimum requirements for cfm/person
and
> cfm/area.  However, the way eQuest calculates min zone OA is by taking
> the higher value of either OA-FLOW/PER or OA-FLOW/AREA, not the
combine
> total.  To correctly model the OA requirement, I have to calculate the
> combine OA rate (i.e. {[cfm/per * max # of person] + [cfm/area * floor
> area] } / floor area) and input that value in OA-FLOW/AREA.  Now, the
> problem comes in when we include DCV into the model, at which eQuest
> cannot calculate the savings because the OA-FLOW/PER value is not
> entered.  I would greatly appreciate it if anyone can clarify this.
>
>
>
> VICTOR YEUNG, BASc, LEED(r) AP
>
> EIT - LEED(r)/Sustainable Development
>
> victor at invirosystems.ca <mailto:victor at invirosystems...ca>
>
>
>
>
>
> From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
> Sent: April 28, 2010 11:16 AM
> To: Rob Hudson
> Cc: equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] Demand Controlled Ventilation
>
>
>
> Rob,
>
>
>
> You need to set up an hourly report. See attached.
>
>
>
> Bill
>
>
>
> ________________________________
>
> From: Rob Hudson [mailto:rdh4176 at gmail.com]
> Sent: Wednesday, April 28, 2010 11:06 AM
> To: Bishop, Bill
> Cc: equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] Demand Controlled Ventilation
>
>
>
> How can i tell if the system is using a lower OA CFM during the less
> occupied times?
>
> On Wed, Apr 28, 2010 at 10:43 AM, Bishop, Bill
> <wbishop at pathfinder-ea.com> wrote:
>
> Rob,
>
>
>
> I recently modeled DCV successfully for the first time. (I showed
> savings anyway.) You need to enter zone-level OA as OA-FLOW/PER and/or
> OA-FLOW/AREA. The OA flow/per (person) is what will get you the
savings,
> based on your occupancy schedule(s). I also created a MIN-AIR-SCH,
> coinciding with the fan schedule, set to zero when fan is off and -999
> when fan is on.
>
>
>
> Regards,
>
> Bill
>
>
>
> William Bishop, EIT, BEMP, LEED(r) AP | Pathfinder Engineers &
> Architects LLP
>
> Mechanical Engineer
>
>
>
> 134 South Fitzhugh Street
> Rochester, NY 14608
> T: (585) 325-6004 Ext. 114
> F: (585) 325-6005
>
> wbishop at pathfinder-ea.com
>
> www..pathfinder-ea.com <http://www.pathfinder-ea.com>
>
> P Please strive to live sustainably.
>
> ________________________________
>
> From: equest-users-bounces at lists.onebuilding.org
> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rob
> Hudson
> Sent: Wednesday, April 28, 2010 9:55 AM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] Demand Controlled Ventilation
>
>
>
> I am having some trouble with setting up DCV in my model.  if i select
> DCV in Zone Sensors for the Min OA Control Method and a min outside
Air
> Ratio, do i need any Zone level OA inputs?
> Any help or insight as to what inputs are necessary for DCV would be
> great!
>
> --
> Rob Hudson
>
>
>
>
> --
> Rob Hudson
>
>
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