Miroslav,
This appears to be a novel and correct method of modeling a “DOAS” system which provides outdoor air to zones served by a VAV system, using the ZoneMixing objects.
Most of the time DOAS works with zone-based HVAC, such as VRF or fan coils and the “one loop per zone” limitation is not a concern. For your system, it would be a problem, but I think you have overcome it. Congratulations on a creative solution.
I think that nothing in LEED or ASHRAE 90.1 will address this specific situation, but you have made a thermodynamic equivalent which should be easy to defend if any reviewer asks for details. I doubt, however, that anyone will ask!
James V Dirkes II, PE, BEMP, LEED AP
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 Miroslav Bratanov
Sent: Wednesday, December 12, 2012 9:24 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Re: ASHRAE 90.1 G3.1.1
Dear all,
May I ask your opinion concerning a possible solution that I have to this old thread and another one also asked by me "Is it possible to model a ventilation system in EPlus, which supplies air to one zone and extracts the same amount of air from another zone?"?
As I have mentioned before in the EPlus group I have to model a constant air volume system that supplies air to one zone and extracts the same amount from another. I also have other zones connected to this system. The zones are heated only (no cooling) and the project is for LEED and follows ASHRAE 90.1 Appendix G procedure. The baseline model system is VAV+Reheat. I have to add identical cooling system to my proposed model. I've tried many different scenarios to do it but neither of them has worked for one reason or another.
I have stopped at this one now, and I think it is the closest to the real situation. Please, see the attached scheme.
Since I can't use more than one air loop for the same zone in EnergyPlus, I decided to supply the air from the CAV system to a separate ideally insulated zone and then using ZoneMixing objects to supply it to the other zones. This allows supplying air to one zone and extracting it from another. And also leaves the AirLoopHVAC for the VAV system which requires more specific control.
Do you think this scenario will work and will it be OK for LEED?
Thank you very much!
Miroslav
From: Jean marais <jeannieboef@xxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Sunday, May 6, 2012 10:23 PM
Subject: [EnergyPlus_Support] Re: ASHRAE 90.1 G3.1.1
Could you include the componants of the additional cooling system inline with your current system, I.e. even if your ahu is serving multiple floors, if you included a dx unit inline with it and vav dampers with reheat at the zones, then you have added a cooling system on each floor. Where does one HVAC system end an another begin really. This kind of thing is so irritating. it doesn't help anyone. I share your frustration.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jim Dirkes" <jim@...> wrote:
>
> Miroslav,
>
> I think that making the cooling setpoint high (e.g., 30C) is not sneaky.
> The approach recognizes the actual situation and provides a realistic
> comparison between the two systems.
>
> I am pretty sure that modelers other than I have used this approach and I
> think I have seen a LEED CIR on the topic which indicates it's OK. I do not
> know the intentions of ASHRAE's 90.1 authors.
>
> p.s. Nothing I say above is definitive - it's opinion. Defensible and
> realistic, but opinion nonetheless. The authors of 90.1 did a very good
> job, but I have never seen or heard an explanation of this particular
> 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 Marcus
> Sent: Sunday, May 06, 2012 12:29 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] ASHRAE 90.1 G3.1.1
>
>
>
>
>
> Hi Miroslav,
>
> Yes, now I see your dilemma! I have never experienced this, but have some
> thoughts;
>
> One overriding concern is the number of unmet hours. If you have no cooling
> system in your proposed design, do you still meet G3.1.2.2 unmet hours? If
> you do, you can argue that your proposed design for whatever reason does in
> fact not require any cooling. And it follows that you can model the proposed
> system and simply turn the cooling setpoint up so high that the system never
> turns on. This of course is equivalent to not having any cooling system, and
> therefore maybe you... forgot to model it...
>
> This argument is one that I have seen on the bldg-sim list, but I have never
> needed, nor can I vouch for it, since it seems a little sneaky.
>
> If you do need cooling to meet unmet hours, another method might be to just
> throw in a PTAC unit in each zone. Packaged VAV has DX cooling, as does
> PTAC, so maybe you could argue that this meets the requirement for Table
> G3.1 10.d. I guess it depends on how you strictly read "cooling system shall
> be identical".
>
> So again, I don't have any experience with this exact problem, you might
> want to get official confirmation!
>
> Cheers,
>
> Marcus
> --
> Marcus Jones, M.Sc., LEEDRAP BD+C
> Freelance energy consultant
> Vienna, Austria
>
> On Sun, May 6, 2012 at 10:52 AM, Miroslav Bratanov
> <miroslav_bratanov@...> wrote:
>
>
>
> Thanks for your reply and directions, Marcus!
>
> But it is the proposed model that bothers me. And this is why:
>
> The building that I am modeling has only heating and outdoor air systems.
> Some spaces have heating only and others have heating and outdoor air
> supply.
> The heating system is with radiators, so following Table G3.1.10b for the
> Proposed Building Performance "Where an HVAC system has been designed, the
> HVAC model shall be consistent with design documents..." I have modeled the
> heating system using Baseboard:Convective:Water and the outdoor air systems
> using AirLoopHVAC.
>
> The building does not have a cooling system designed, but Table G3.1.1b says
> that "All conditioned spaces in the proposed design shall be simulated as
> being both heated and cooled, even if no heating or cooling system is to be
> installed...".
> Also Table 3.1.10d says for the Proposed Building Performance that "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".
> From this I understand that my proposed design model shall have the systems
> as they are given in the design documents plus Packaged VAV with Reheat for
> the cooling. In other words the proposed model shall include the radiator
> heating system, outdoor air systems and also packaged VAV with reheat.
> Correct me if I am wrong, please!
>
> Currently in my proposed model I have the following systems for each floor:
> Baseboard:Convective:Water for all zones that have radiators only
> Baseboard:Convective:Water and AirLoopHVAC for all zones that have radiators
> and outdoor air supply systems
> Also I have one AirLoopHVAC that connects zones located on two different
> floors.
> Thus, I fulfill the requirements of Table G3.1.10b for the Proposed Building
> Performance "Where an HVAC system has been designed, the HVAC model shall be
> consistent with design documents..."
>
> Now, the problem is how to add the Packaged VAV with Reheat to the proposed
> model in order to fulfill the requirements of Table 3.1.10d for the Proposed
> Building Performance "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"?
>
> If I am allowed to use only one Packaged VAV with reheat for each floor, I
> can not think of a way to add it to all other AirLoopHVACs that are already
> used to model the outdoor air systems.
>
> Thank you!
> Miroslav
>
>
>
> On 5.05.2012 18:46, Marcus wrote:
>
>
>
> Hi Miroslav,
>
> Yes, you can only have one packaged unit per floor. After you know your
> baseline system type, forget about your proposed HVAC system. The baseline
> system is a completely new system providing heating, cooling, and
> ventilation, and has no elements of your proposed system.
>
> Fortunately, you can easily model system 5 with the
> HVACTemplate:System:PackagedVAV and associated objects. So take your
> proposed.idf file, and delete all the HVAC components so you are just left
> with geometry and loads, then apply the HVACTemplate:System,
> HVACTemplate:Plant:Boiler, and finally the HVACTemplate:Zone:VAV objects to
> each zone. See the appropriate example file in the /examples directory.
>
> Let me know how it goes, and best regards from Vienna!
>
> Marcus
> --
> Marcus Jones, M.Sc., LEEDRAP BD+C
> Freelance energy consultant
> Vienna, Austria
>
>
>
> On Sat, May 5, 2012 at 3:47 PM, Miroslav Bratanov
> <miroslav_bratanov@...> wrote:
>
>
>
> Hello Everyone,
>
> I am modeling a 3 storeyed building for LEED. There is no cooling system
> in the building and according to Table G3.1 of ASHRAE 90.1-2007 for the
> proposed design model I have to use the same cooling system as in the
> baseline design.
> The system for my baseline design is Packaged VAV with Reheat and also
> according G3.1.1 "each floor shall be modeled with its own HVAC system".
>
> Does "each floor shall be modeled with its own HVAC system" mean that
> the baseline model can have only one HVAC system for each floor?
>
> In my proposed design model, there are more than three outdoor air
> systems on each floor. Each of these systems uses AirLoopHVAC. I know
> that I can add more than one branch on an AirLoopHVAC but still I would
> have to add a separate Packaged VAV with Reheat for each existing
> AirLoopHVAC on the same floor which means more than one Packaged VAV
> with Reheat per floor.
>
> Another problem is that in my proposed design model there is an
> AirLoopHVAC that supplies fresh air to spaces on two different floors.
> If I add the Packaged VAV with Reheat to the existing AirLoopHVAC then
> it won't comply with G3.1.1. How to model the cooling system then?
>
> Has anyone had such or similar case and what would be the solution?
> Any help is appreciated!
>
> Miroslav
>
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