How should dedicated sub-cooling chillers be modeled using ECB?

edit

I have a dedicated water-cooled brine chiller supplying 38F water to a coil in the OA stream for an OR. I'm not sure what the correct way to consider this in creating my ECB HVAC system. My first inclination is to model the brine chiller making 38F water, but serving the single mixed air cooling coils for an ECB system 2. I can't find any guidance to back it up though.