One of the very first things I was taught when I started in this game is that the mains fuse protects the mains cable, not the equipment. The medical standards state the requirements for equipment fusing. Hence the requirement to fuse at, or below, the continuous current rating of the cable. Well worth making clear to all of those techs never having done EST, possibly having to pick it up as they go along.
Yes John, I don't see 13A rated, moulded, IEC leads around. The cables and moulded IEC connector are rated IEC at 10A maximum, as far as I can tell. The 13A rewireable IEC connectors that you see on kettles are not recommended for Medical Equipment - wasn't there a purge to remove these, on MDA advice, a good few years ago? I don't think it good practice to manufacture 13A rated IEC leads for general use. Moulded leads seem to be a better idea, as you say yourself.
However there are general concerns about the quality of the strain relief on the IEC connector from all manufacturers (usually sheath pulls away from strain relief, exposing the seperate, insulated, conductors) or the connector disintergrates around the holes where the male IEC connector pins enter the moulded IEC. Some individuals also worry about the quality of the connections inside the moulded plugs, from experience of problems, so they remove the moulded plugs and replace with rewireable plug tops.
Rog: The length of IECs is limited by the earth-bond resistance limit in practice - of course this is dictated by the cross-sectional area of the earth-conductor isn't it? I think the earth-bond limit for the detachable IEC itself is effectively 0.1 Ohm if the earth-bond from the appliance IEC connector earth terminal to accessible earthed parts of the instrument approaches the 0.1 Ohm limit speciified in the general standards for medical equipement i.e. 0.2 Ohm overall, when connected to the instrument, checking it as part of the system. Since leads can move around then I guess if you allow 0.2 Ohm earth-bond for the IEC lead then there is a possibility of particular instrument/IEC lead combinations equipment failing the earth bond test. Does anybody have any views on this? I suppose, in this case, if it fails then replace it.
Perhaps Alex has the right idea when he says that the policy at the hospital where he works is to retain the IEC lead to the equipment. Incidentally; what are people doing about inspection, testing, rating and on-going maintenance of multi-socket extension blocks? Does anybody actually suggest the users purchase or use them? Is the use of them actually acceptable in these days or just a necessity? Do we turn a blind-eye to this practice or what?
A longer lead necessitates the use of 13A rated cable (to increase earth-conductor cross-sectional area, to reduce electrical resistance) and appropriately rated (mechanically and electrically) rewireable IEC connector. I think the use of excessively long leads should be frowned upon. Rewirable 13A IEC connectors are not particularly good connectors, electrically or mechanically, in my opinion. I say bring the power-source i.e. sockets, to the equipment. Long leads can give problems due to damage from being run-over, twisting leading to conductors being exposed through the outer sheath and the possibility of self-heating of the cable (at higher loads) when coiled incorrectly. Again; there have been warnings from the MDA, I think, about the inappropriate use of coiled extensions, long cables and suchlike.