Re: [EnergyPlus_Support] Re: Ventilation Requirements per ASHRAE 90.1 Appendix G with a DOAS system

On Tue, Apr 3, 2012 at 3:47 PM, curtisjclark <cjcfromslc@xxxxxxxxx> wrote:

Jim,

For a 100% Outdoor Air System (Proposed) the formula is:

Vot = Sum(Voz) 'Sum of the zone

DOAS outside air = sum of all zones Outside air.

For Multi-Zone Recirculating (Baseline) the formula is:

Vot = Vou/Ev 'Uncorrected outdoor air rate / Ventilation efficiency

The above equation is good for single zone VAV system, not multi zone VAV system

(per std62.1)In multizone Vot= Vou/Ev , here Vou = sum of all zones outside air requirement, Ev would be less than 1 as effectiveness drops for multizone system.

Ev = 1+ Xs-Zd, where Xs=Vou/Vps, Zd = Voz/Vdz

If we set the outdoor air requirements at the zone level (Voz) for both models to be equal, Vot of the Baseline will not equal Vot of the Proposed.

Ev would be less than 1 and Vot for VAV > Vot chilled beam system (logically i would expect multizone VAV system has higher outside intake value than chilled beam).

This may not satisfy requirement of ASHRAE Appendix G3.1.2.6 for ventilation as states:

Vot (Baseline) = Vot (Proposed)

If we force the issue and set the Vot of Baseline to the Vot of the Proposed, we will not meet the requirement of ASHRAE 62.1 for the Baseline model.

Try inputting OA at system level rather than at zone level.

In addition, how is EnergyPlus reporting outdoor air because the two reports (Controller:OutdoorAir and Minimum Outdoor Air) are not consistent. I suspect that the Controller:OutdoorAir reports the Vou for a Multi-Zone Recirculating system, not the Vot.

if manual calculation per std 62.1 is done then Vot> Vou, but i suspect the software is just throttling down OA in proportion to reduced airflow at part load condition or occupied hours ( if zone level air flow is entered as % of supply airflow).

I am not quite sure if above make sense, as i'm in dark how you've setup the model.

ny insights would be appreciated.

CURTIS CLARK PE, LEED AP BD+C
SUSTAINABILITY SERVICES
GSBS Architects

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jim Dirkes" <jim@...> wrote:
>
> Dear Curtis,
>
> I am not familiar with the report you mention. Where does it come from? And
> what does it measure?
>
> On the other hand, you seem to have answered at least part your own question
> by noting that minimums were identical for each of the two systems. Can you
> run a 62.1 compliance check? Or get it from the design engineer? To see if
> your minimum flows meet the 62.1 requirement?
>
>
>
> The Building Performance Team
> James V. Dirkes II, P.E., BEMP , LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
>
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of curtisjclark
> Sent: Tuesday, April 03, 2012 12:40 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Ventilation Requirements per ASHRAE 90.1
> Appendix G with a DOAS system
>
>
>
>
>
> Each zone is hardwired using DesignSpecification:OutdoorAir object using
> "Flow/Area" values.
>
> Curtis
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , Vinay Devanathan

> <vinay.devanathan@> wrote:
> >
> > You could hardwire the same OA cfm for each zone to what it is in the
> > design case.
> >
> > On Tue, Apr 3, 2012 at 11:55 AM, curtisjclark <cjcfromslc@> wrote:
> >
> > > **
> > >
> > >
> > > We are using a DOAS system which delivers 100% outdoor air to the space.
> > > In the Baseline model (appendix G), it is a VAV system which delivers
> mixed
> > > outdoor air with return air.
> > >
> > > To meet the requirements of ASHRAE 62.1 in the Baseline model, I used
> the
> > > Ventilation Rate Procedure calculation method to determine the minimum
> > > outdoor air by using the Controller:MechanicalVentilation object with
> the
> > > same ventilation rates as in the DOAS system.
> > >
> > > The report for "Controller:OutdoorAir" shows the two system have same
> > > Minimum Outdoor Air Flow Rate. However, the report "Minimum Outdoor Air
> > > During Occupied Hours" shows a 84% reduction in outdoor air.
> > >
> > > Have I meet the requirements of Appendix G3.1.2.6 for ventilation?
> > >
> > >
> > >
> >
> >
> >
> > --
> > Vinay Dev
> >
>