I'm modeling a large office building that will be using chilled beams. There will be two water-cooled chillers equally sized. I've created a baseline model per App G System 8 (VAV with PFP boxes) and each chiller comes out at 350 tons.
I then used that model to create the building model using chilled beams. Instead of a dedicated chiller supplying 58°F CHW for the chilled beams and a dedicated chiller supplying 42°F CHW for the OA units, we're only producing a CHWT of 42°F. Then we'll use a heat exchanger to create a tempered CHW loop at 58°F for the chilled beams. When I run the model, my chillers become grossly oversized at 734 tons each. When I look at my total coil load (OA units plus chilled beam) the design load is only 679 tons so I'm not sure why the chillers are being oversized so much. My oversize factor is set at 15% (per App. G) and all the coils & chillers are set to autosize.
Has anyone run into this issue? Much thanks in advance for any input.
