District Energy for Partial Building Load

You would only model the campus sources according the the DES. You can use either DES option to model them. The baseline is according to G3.1.1 and the DES guidance. Since the primary heat source is heat recovery that sounds like other to me so use that column from G3.1.1A. If you use DES Option 1 then the campus systems are purchased energy, if Option 2 then model the baseline as described there. If there is some sort of conflict in the baseline system choice then ask again with more specifics.

No but it is a fuel source which is likely from fossil fuels. The question is whether your system is electric/other or fossil fuel/hybrid. After thinking this through some more I think it is hybrid assuming the fuel source for the district steam is a fossil fuel. I considered splitting the systems and having separate baseline systems but there is no justification for that in Appendix G or the DES. I also considered whether it would be electric/other but since there are fossil fuels contributing to the heating it becomes hybrid. I also think it is not fair to be comparing the system you describe to electric resistance heat in terms of a reasonable accounting for the savings.

I have a similar question; the 135000 SF building is served partially by HRC and is supplemented by campus CHW. The HRC is sized at 250 TONS to take care of heating load, the overall building load is estimated to be 450 TONS. Looking more into the details, the campus CHW supplements the building cooling 1065 hours in a year, accounting for 12% of the total cooling Tonnage. HRC capacity is enough to take care of the building cooling load rest of the time (7695 hrs). When there is no cooling demand for the building, the HRC feeds back the campus. The estimated cooling tons back to the campus is a total of 850,000 TONS. Vs the 100,550 total tons supplemented by the Campus CHW to take care of this building peak cooling load.

1. Based on the building type, ASHRAE 90.1 2010 and all electric HRC system, the baseline system would be system 6. Could you please confirm. I see that in 2013 ASHRAE, the baseline system type selection is based on climate & not the heating/cooling source. Is there an addendum to meet the newer code?
2. Since, the CHW is supplemented for peak load, are we supposed to use DES guidelines assuming CHW & HW coils instead of DX coil. In that case, the baseline system would become VAV reheat (system 8). Since the proposed HRC is feeding back into the campus, we would be penalized for using an efficient system and adding back to the campus if we were to use System 8
3. If I had to use DES system path 2, how should I model the baseline & proposed case? Proposed model =Cooling, Campus Chilled water system and HRC; Heating, Natural gas boilers at campus & HRC at building level and baseline would be as per Appendix G?

1. System 6 sounds right. If it was added as an addendum then you could use it, if not then you can't. You can use all of 2013 if that is your local code requirement and apply the adjusted point scale (LI #10481). 2. You do need to use the DES guidelines for the Proposed Case. Our guess is that the baseline would be the electric system 6 unmodified.  3. Not sure why you are including the campus boilers if the HRC provides all of the building's heating? But yes the baseline is per App G.

see below

Hi, I have a similar situation where my project is using chilled water from a central plant for the majority of the project but is also adding a chiller as the central plant doesn't have enough capacity for the entire building. I am modeling the district energy using Path 1, but am not super clear on how to create the Appendix G baseline. You mentioned above "I considered splitting the systems and having separate baseline systems but there is no justification for that in Appendix G or the DES" which makes it sound like I should not add a chiller to the baseline as I have modeled in the proposed. So my question is: 1. Since the district energy system is the primary chilled water source for the proposed, is it the total chilled water source for the baseline? Should I follow G3.1.1.3.2 Purchase Chilled Water and have all the chilled water in the baseline served by a district energy system? 

I would suggest modeling both a purchased chilled water plant and an on-site chiller plant in the Baseline, sized according to the same proportions that each of those plants meets the loads in the Proposed Case.

I am facing a similar situation in a LEED v4.1 project, where all the space cooling is served by District Chilled Water, except for a server room which is cooled by an electrically operated CRAC. Your last comments and the common sense lead me to think that the right approach for the baseline would be to model it in a similar way, splitting the cooling system by source: the corresponding main system according to Table G3.1.1-3, served by District Cooling, for all spaces and an electrically operated System 4 (according to our climate zone) for the server room (that, in our case, matches as well the provisions for section G3.1.1 g.). Do you think that is a correct approach? Thank you.