How to model process cooling with ASHRAE 90.1 App G Baseline system 5 or 6

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I am going to second @Anna 's approach that Option 2 is more appropriate. Only modification I'd make is that the process chiller EER/COP should match the Proposed chiller's efficiency. This would help make the process loads equal between the baseline and proposed. May have to look at loading curves as well...

Only other element might be if there is a DES. Nothing indicates that in the question, but in many cases our models with Labs are on a DES/Campus system.

Agreed. Modeling the same rated cooling efficiency with an auto-sized chiller capacity in the Baseline model should be good enough in most cases. In some cases, when the cooling load dynamic is much different between the Baseline and Proposed models, I would calculate the average cooling efficiency in the Proposed model and apply that to the cooling process load in the Baseline model. This may not be necessary though.

Yes, the proposed case space cooling is met with a system with CHW coils and the process cooling is served by the same cooling plant. No DES.

Following the logic from the comments above in keeping the efficiency of the chiller the same as in the proposed case, would I also want to use the same W/gpm as the proposed model?

Also, the project is located in a cold climate and will use dry coolers in the colder months for free cooling. Would I be justified in excluding the free cooling from the baseline cooling plant when modeling either explicitly or using an average cooling efficiency?

That's a tough one. For the pumps I would match the kW/GPM of the proposed, in the effort to keep them as close as possible. For the dry cooler, I think you have two options. The first would be to model the same CHW configuration as the proposed, Chiller & dry cooler, at the same efficiencies. This makes it the easier to directly compare the two, though with chiller curves & loading the two plants will (most likely) run differently. The more difficult path would be to determine the average Proposed chiller efficiency and model that chiller in the Baseline. (cont)

Then implement a 'flat' performance curve. Similar to the DES Option 1 in LEEDv2009 OR DES Option 1 Path 3 in LEED v4. (Streamlined, averaged efficiency DES plant simulation). This method would use the Proposed chiller plant average load efficiency, ignoring how the comfort vs process cooling demand might load the plant differently. The overall, average efficiency for the plant. The down fall of this is that it makes the baseline & proposed different (and moderately difficult to explain). Personally...I'd take the first approach and match the efficiencies of chiller & drycooler...and run...