Ken, Unfortunately I do not have access to up-to-date rules and regs. concerning Isolation systems in England/Europe. It seems it is actually a controversial issue in some other parts and in Canada, for one, they have been discussing (on an informal basis?) whether having them, for the little benefit offered, really warrants the cost of them, both capital and running expenses. Probably because the original reason for them (avoiding explosion) has all but gone now. Since it cannot be relied upon to help in micro-shock (leakage current) reduction, this leaves nothing much of advantage, except macro-current reduction. If one does use flammable agents then the reduction in macro current is a plus (spark prevention). Also in the same fault scenario i.e. in the event that a machine does actually go live to ground internally say, a whole power circuit, with its associated equipment connected to it, does not get switched off as it would if the same thing happened in a non-isolated area. In this case, only the offending piece of kit needs to be pulled out of the wall socket when the alarm goes off. Very convenient in theatre situations.
As to your new theatres. I would expect the NHS to have fitted out their "electricals' commensurate with the latest guidelines set up for isolated areas. As the new theatres have come with (hopefully a restricted?) mixture of supplies, then it would appear to be acceptable. Not working either in England or in the NHS I do not know if they now insist on dedicated (alternative socket / pin arrangement) power sockets for floor cleaners and portable x-ray units. Floor cleaners being heavy-current "dudes' and not used, for obvious reasons, during procedures, then it would make sense to have these powered separately using a non-isolated supply. Additionally, if different sockets are used to the normal type, they could not have medical equipment plugged in by mistake. In the case of the x-ray viewers, I would imagine that the inductive circuits of these florescent lights cause unwanted extra leakage current-to-earth in isolated systems. If the x-ray viewer uses the same type of sockets as the other medical equipment in the theatre (even though the associated socket is likely to always have the viewer plugged into it) you perhaps should advise the staff, on the grounds of safety, not to plug medical equipment into it/them unless they are absolutely desperate for a socket. Presumably, all these non-isolated sockets are labeled as such? If however they are not marked, it would be a good idea to mark them clearly.
I would be interested to know if anything else is allowed, officially, to be connected to your non-isolated sockets, besides these two items. Hopefully the staff are restricted in what they are allowed to plug into which power system??
Yes it does sound as if there are a few MCB's that need re-assessment in the area of delayed trip time as it looks, judging by the amount of adverse findings noted in this forum alone, that isolation systems are not reliable, which should definitely not be the case.
If, in your hunt to sort out your particular problems you come up with any interesting info/references on rules and regs of isolated systems. I, for one, would be interested to know too, thanks.
