# VRF performance curve question

I am trying to create and import VRF system performance curve into Openstudio. There are some great articles from FSEC about VRF model in EP. I have several questions about:

Cooling/heating combination ratio correction factor curve : There are 2 separated zones for that curve : one for PLR <= 1 and one for PLR >1 but there is only one input for curve (different with Cooling energy input ratio modifier function of Low/high part-load ratio curve which are individually curves input for PLR <=1 and PLR >1). I have question that if combination ratio installed capacity (ID cooling capacity / OD cooling capacity) >1 but most of time , the system has never reached PLR >1 (because of load profile and sizing factors) so will simulation get right result with PLR >1 curve or

**we must change Cooling/heating combination ratio correction factor curve inside HVAC iteration loops by EMS**for annual period (weather file) simulation?Cooling capacity ratio boundary curve and cooling boundary ratio boundary curve: what's difference between 2 curves? I see that they have same coefficient values in default OS VRF setup

Indoor VRF terminal DX cooling coil model has much differences with normal DX coil (PTHP, unitary,...), is it right?

Input for new VRF model added in EP 8.4 : May we keep the old performance curve or need to renew them all? is there any guide for configuration new VRF model in 8.4?