Hi Paul.
I have just tested the same custom collector specifications (Area: 2.5 m2,FRta: 0.7, FRUL: 4) on the latest SAM version: "Version 2015.6.30, 64 bit, updated to revision 4". And it calculates the same "Rated system size": 1.45 kW.
Here is the file:
www.dropbox.com/s/5rufduh6atl93ga/swh_rating.sam?dl=0
Does this mean that the mentioned formula from the help file:
Nameplate Capacity = Total Collector Area × FRta - FRUL × 30/1000
is incorrect?
Because it outputs 1.63 kW for the same upper custom collector specifications (Area: 2.5 m2,FRta: 0.7, FRUL: 4).