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[EnergyPlus_Support] Re: Two AHUs for a zone
To my knowledge, the LEED reviewers are more concerned that heating and cooling are available. If you have to add cooling, add it to your current configuration. It will catch the unmet loads, and that is the intent. As far as I understand this is a known "bug" in the rating system.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim Dirkes <jim@...> wrote:
>
> Francesco,
> If I were in that situation, This is what I would do:
>
> Proposed
> Heat recovery + preheat + humidifier + heating coils + 2 fans
> DX cooling with room setpoint = 50C and proposed ventilation control (I am guessing that the system uses 100% outdoor air in the cooling season, so the ventilation system is providing all of the cooling)
>
> Baseline
> System 4 in each zone with cooling room setpoint = 50C and ventilation control same as proposed system (for the same effective cooling)
>
> It makes no sense to me to create an artificial cooling system that consumes energy where none exists! My rationale is that the client's comfort criteria are relaxed such that "no cooling" or only ventilation-provided cooling is acceptable. You could say that their design criteria are such that they will accept 50C as their cooling setpoint (even though it is unlikely ever to occur). This results in an energy model that provides a reasonable comparison between the two options. If you make an artificial cooling system, you might double the total energy and completely destroy the comparison.
> I am fairly sure that this approach has been considered acceptable by LEED reviewers. Regardless of whether they like it or not, it strikes me as completely backward to do other than make a comparison which is realistic.
>
> James V Dirkes II, PE, BEMP, LEED AP
> www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of FrancescoP
> Sent: Tuesday, October 23, 2012 11:48 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Two AHUs for a zone
>
>
>
> Hello James,
> the problem regards the model of the proposed building. There is an AHU that is connected to a lot of zones. That AHU doesn't have any cooling system. In fact, the proposed AHU has a heat recovery system, a preheat coil, a humidifier, a heating coil, and two fans (constant velocity).
> The baseline system has to be System 4 - PSZ-HP. To meet the setpoint temperatures I have to model a PSZ-HP system for every zone.
> About the model of the proposed building table G3.1 point 10.d states: "Where no cooling system exists or no cooling system has been specified, the cooling system shall be identical to the system modeled in the baseline building design". Therefore I have to model a System 4 - PSZ-HP as cooling system also for the model relative to the proposed building. I thought that I could connect every zone to the real AHU as heating system and to a virtual PSZ-HP system in order to have cooling, but if I cannot model two air loops serving a single zone I have to look for another solution. I don't know if adding a virtual DX cooling in the proposed AHU is a good solution, because the proposed AHU is connected to a lot of zones, while every PSZ-HP system of the baseline is connected only to a single zone. But does a better solution exist?
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>, Jim Dirkes <jim@<mailto:jim@>> wrote:
> >
> > Dear Francesco,
> >
> > * I do not think it is possible to model two air loops serving a single zone
> >
> > * You can model one Air Loop plus one type of Zone equipment (e.g. PTAC)
> >
> > * I cannot think what requirement of Appendix G would require such a system
> >
> > James V Dirkes II, PE, BEMP, LEED AP
> > www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
> > Energy Analysis, Commissioning & Training Services
> > 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > 616 450 8653
> >
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>] On Behalf Of FrancescoP
> > Sent: Tuesday, October 23, 2012 10:46 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>
> > Subject: [EnergyPlus_Support] Two AHUs for a zone
> >
> >
> >
> > I would like to model a zone as connected to two different AHUs, one AHU with heating coil and the other one with cooling coil (it isn't a real HVAC system; this model is for ANNEX G of ASHRAE 90.1-2007). Is it possible? How should I specify the ZoneHVAC:Equipmentconnections? Should I specify the two inlet nodes in the same nodelist? Should the "zone retuen air node name" be the same for the two systems?
> > Do you know if there is an example file with such a situation, please?
> > With Regards
> >
>
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