[Equest-users] Demand Controlled Ventilation

[Victor Yeung]

Thanks Rohini.  Depending on the number you use for the cfm/person, your
method will end up over/underestimating the space cfm requirement.  I
guess I have to conclude by saying this is a limitation of eQuest at the
moment.  What I have been thinking about doing is to calculate the avg
number of person per zone per hr based on the occupancy schedule, and
use that avg to calculate my effective total OA rate.  It will be
extremely tedious, but at least it should be accurate.

Thanks everyone for their input.

Victor

-----Original Message-----
From: R B [mailto:slv3sat at gmail.com] 
Sent: April 28, 2010 2:36 PM
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
>
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>
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>
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>
>
>
>
> 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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