Never seen those either. Is it really a PTW thing or a site-specific choice?
Maybe HRC 2A asks for 8 cal/cm^2 of protection and HRC 2B asks for 12 cal/cm^2 of protection. It is at least plausible.

Unfortunately ETAP, Easypower and SKM have WRONGLY included H/RCs in the software results table for incident energy results. It should not be there and should not show up on labels.

If you complete engineering incident energy analysis the electrician selects arc rated clothing based on the incident energy and working distance indicated on the label.

In your company's Electrical Safety Program define arc rated clothing by a "Level #." Level 0, Level 1 and Level 2 only. If you use the hazard/risk category tables then these levels would correlate to H/RC #s.

You cannot use the hazard/risk category information in 70E or CSA Z462 when you have engineering incident energy analysis completed.

Regards;
Terry Becker, P.Eng.
[url="http://www.esps.ca"]www.esps.ca[/url]

I assume you are talking about SKM PTW. Have you contacted SKM about this? They would be the ones to explain the meaning of HRC 2A or HRC 2B... I suspect it refers to a specific customer designation.
It is my experience that most of the software companies are very careful about using HRC designations on labels. Most of the labels I have seen, specifically say "PPE Category", or just "Category" so that workers can easily determine what PPE to use, if working on the equipment while energized.
HRC or Hazard Risk Categories only apply for a specific task. The HRC can vary from HRC 0 to HRC 4 for the same equipment, depending on the task being performed. According to NFPA 70E, If labels contain a Hazard Risk Category, it must be the highest Hazard Risk Category that applies for any task on the equipment being worked on.

I'm guessing 2A refers to category 2 and 2B refers to category 2* in NFPA70E-2009. PTW still refers to the 2009 version of NFPA70E in the arc flash results summary tables etc. The 2 and 2* categories differentiation was removed during the 2012 update to NFPA70E.

And yes, SKM need to update their software.

If I have this wrong, feel free to set me right ...