Re: [EnergyPlus_Support] ASHRAE 90.1 G3.1.1

On Sun, May 6, 2012 at 10:52 AM, Miroslav Bratanov <miroslav_bratanov@xxxxxxxxx> 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., LEED^®AP BD+C
Freelance energy consultant
Vienna, Austria

On Sat, May 5, 2012 at 3:47 PM, Miroslav Bratanov <miroslav_bratanov@xxxxxxxxx> 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