[Equest-users] Demand Controlled Ventilation

[Victor Yeung]

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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