Add preheat coils to VAV systems in prototypes

[mdahlhausen]

The main supply heating coils for the air loops in the original DOE prototype models use a default 55F inlet/104F outlet air temperature. The openstudio-standards models assume a 45F inlet/55F outlet, matched to typical design drawings. This causes some coils to not have enough heating capacity in cold climates when the global heating sizing factor is set to 1, leading to unmet hours. Possible solutions are:

1. Use the original sizing air temperatures (non-optimal, as it leads to oversized coils / systems)
2. Drop the design inlet air temperature to some lower value, e.g. 30F (non-optimal; could lead to oversizing)
3. Add a pre-heat coil (preferred approach)

[lymereJ]

@mdahlhausen, have you noticed unmet load hours in all prototypes in cold climates or in specific prototypes? Thanks!

[mdahlhausen]

@lymereJ I've found it in most prototypes (LargeHotel, LargeOffice, MediumOffice, SmallOffice, Outpatient, Hospital, RetailStandalone, SmallHotel, Warehouse) in cold climates with VAV-based systems. A representative one is the LargeOffice ASHRAE 90.1-2004 Prototype in Climate Zone 8.