# DX coil sizing and part-load flow component

1/ I continuously get error for autosize a 2 Stage DX cooling coil with dehumidification control if I enable DX DOAS option in CoilSystem: DX cooling. The error describes following statements:

COILPERFORMANCE:DX:COOLING "DOAS DEHUMID PERF 1" -- coil bypass factor calculation did not converge after max iterations.The RatedSHR of [0.556], entered by the user or autosized (see *.eio file), may be causing this. The line defined by the coil rated inlet air conditions (26.7C drybulb and 19.4C wetbulb) and the RatedSHR (i.e., slope of the line) must intersect the saturation curve of the psychrometric chart. If the RatedSHR is too low, then this intersection may not occur and the coil bypass factor calculation will not converge.

I use all autosize option, it's a DOAS airloop system with ventilation requirement sizing and Cooling load control - VAV I read that it's an energyplus error so how to pass this ? May I hard-size the DX coil and SHR or change the performance curve ?

2/ When I try to reduce the airflow of fan at night when DX coil still work for dehumidification, there are a lot warning for frost coil condition while the dehumidifying load at night is very low. How to solve this problem for DX coil with variable flow fan ?