Enumeration to configure the outdoor/relief/return air section
type OutdoorReliefReturnSection = enumeration(HundredPctOutdoorAir "100 % outdoor air system", MixedAirWithDamper "Mixed air system with return air damper - Optional economizer function", MixedAirNoDamper "Mixed air system without return air damper - No economizer function", MixedAirNoRelief "Mixed air system without relief branch - Optional economizer function");