A: Check the original panel nameplate. It should have a UL file number (e.g., E123456) and sometimes the standard revision date. Contact UL’s customer service with that file number to request the historical standard used during its certification.
The definition of "Low Voltage" was redefined to allow a maximum open-circuit secondary voltage of 60 volts DC . Ul 508a 3rd Edition Pdf
The 3rd Edition of UL 508A was published in 2012. Some key changes include: A: Check the original panel nameplate