Improve GSHP logic

[mdahlhausen]

Currently the GSHP HVAC system uses EMS code to approximate return temperatures from the ground loop. This could be improved by using site specific ground temperature and soil composition. Perhaps there is a simplified regression model to use instead.

In addition to this, the GSHP HVAC system needs a backup boiler and/or chiller. This requires an annual run and more complicated implementation of EMS controls to size and operate this backup properly.

[chrisbalbach]

+1

[mdahlhausen]

There is a ComStock project this year with the geothermal office to add better ground source heat pump modeling to OpenStudio/ComStock. Depending on the results of that project, we may adopt that model in openstudio-standards.