Chris,You are getting somewhat confused here.
The reason the testers limit testing is when the touch voltage under test conditions can exceed that as described in the reg I quote, I did NOT EVER state that RCD's limit touch voltage.
I think that you will find that the 50 volts is "related" to 411.5.3, which will relate back to the IEC std for both installs & the instruments.
We were talking about touch voltage, then you posted the above, this Reg does not place a limit on touch voltage as such, just ensures voltages over 50V are disconnected.The requirement will come from an IEC, probably more to do with the acceptance of 50V being a safe touch voltage.
The work involved in converting the locations to a Group 2 standard would be prohibitive, and extremely expensive.
I do not believe that 710 was ever envisaged for this work.
There are applied parts, the risk of microshock is present, but limited.
IT systems are required for Group 2 locations, however, I don't class the installs I am doing as Group 2 even though 710 does.
To separate and convert the existing install to IT would be a huge upheaval that would not be workable.
A small ups for the required circuits, IPS for the sockets, the earthing shouldn't be to much of a issue, pendants, well you could get around them, surly if there is a risk, then the above is achievable without too much cost?
Still have a few things to finish, only got out of the workshop at 19:00, but, enough for tonight, back at a suppliers for 7:30 then to a couple of others, then back to the workshop all day, and in and out of the office.
Don't have the option of nice hours, have to do the work when it is there to keep the clients happy, especially ]once I commit to a medical job, the time-scale cannot change once confirmed.