Modeling distributed DHW systems

edit

Hi, I'm trying to see if it's possible to model a distributed DHW system for a multifamily building in OS. So there would be one large water heater in a main mechanical room and several smaller water heaters/tanks throughout the building each serving a handful of apartments.

I built a prototypical multifamily building using the gems and then tried just adding water heaters to the demand side. The app does allow the objects to be added there and the service hot water system can be assigned to a specific zone, but there's an error when I try to run that. Based on the error message I think there's probably a connection that's missing

Error I'm seeing when I run this.