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Question on installing US 110v sockets in the UK.

James Doolin

I have been asked to install 110v US NEMA style sockets for a company in the UK who test equipment bound for the US before shipping. To be clear they only require a single phase 110v to 0v supply feeding 15 amp socket outlets and not the split phase 110v 110v system providing 240v from 2 legs. The machines definitely require a 60Hz supply. They have sourced a static frequency and voltage converter (Sinalda FCL-30H-3:S10-SR50 30kVa) which will take a 63 amp 3 phase 4 wire 50Hz supply and convert it to a 230v 60Hz single phase 2 wire supply. This would supply a 3 phase distribution board with single phase link kit and be populated with RCBOs to feed 10 radial circuits feeding a single 15 amp socket per circuit. I have found a board and RCBOs from Schneider which are suitable for 110v 60Hz.
My 2 main questions are - do the RCBOs need to be double pole. They have an existing 110v US style installation using double pole RCBOs, I realise these are required on reduced low voltage 55v-0v-55v installations but don't understand why they would be required in this instance. My second question is regarding the earthing on the secondary side of the voltage frequency converter. The neutral of the secondary side of the converter is referenced to earth as standard. I would like to satisfy myself that this is safe as this is introducing a neutral earth link beyond the incoming supply.
I have realised that there is an issue with the converter the client has specified as it's output is variable so will be asking if it can be replaced for a fixed output model.
I also realise that it is unclear whose regulations I would be working to. I have spoken to my governing body and have been told that although BS7671 wouldn't cover such an installation, if it was installed in line with US regulations they can't see a problem with it. To this end I have found out as much as I can about the US system but realise the limitations of learning from Youtube!
Would appreciate any advice offered as I am a little out of my comfort zone.

  • 0

    Do you really mean a 230V 2-wire output for the static converter?  If so, it'll need another step down transformer for 110V.

  • 0 in reply to Simon Barker

    its one of these
    datasheets. Essentially a very large audio amplifier or AC power supply. 
    Most models allow both voltage and frequency to be configured. 
    You would earth the neutral of the output side, much as you earth the centre of the 55-0-55 RLV system on building site, it is not a connection to supply neutral. This is your own local seconday side neutral at the source, much as you wouild I hope NE bond a large generator.
    I'd suggest the use of US style GFCI would be more sense - the RCDs available in the UK do not all work with 110V supply or 60Hz, or at least are not rated to operate reliably.
    It will be dedicated test equipment and BS7671 will not be the correct standard to apply once you leave 230V 50Hz land and the BS4343 socket that supplies it , - and if you do, it will fail ;-)

    I'd expect it to be a dedicated test bench or similar and the length of the 110V to be short as poss.
    Mike.

  • 0

    Yes sorry that was a typo, the converter will output 110v to 0v single phase not 240v. Have been given a couple of options from Schneider for RCBOs suitable for 110v 60Hz but they are expensive. Had thought of the GFCI socket option but wasn't sure of availability in the uk, the client is already using a MK NEMA 5-15R available from RS.

  • 0

    I'd suggest the use of US style GFCI would be more sense

    Also the US tend to use GFCIs at the socket (receptacle) rated at 5 or 6mA (per faceplate) rather than the 30mA (per circuit) we tend to use ... so if you want assurance the kit will work in US style conditions, be aware that the RCBO approach would likely not object to say a 10mA pulse of leakage, whereas the GFCI might well.

    On another tangent, BS 7671 itself has no problem with 115V installation per se - I guess it's the NEMA sockets are the stumbling point (although the lack of shutters might be less of an issue than in a domestic situation). One approach might be to do it with 115V BS 4343 outlets and provide adaptors (e.g. short length of flex with a NEMA trailing socket on the end) for the NEMA plugs?

       - Andy.

  • 0 in reply to AJJewsbury

    It may or may not comply with BS 7671, but please don't use the bs 4343 style yellow connectors for an earthed neutral 110V - pretty much everyone expects earth centre == split phase or 2 of 3.;-) 

    Personally I'd mail order in a UL certified duplex GFCI socket - the internet is your friend.
    If you really must have joins in the lead then to use IEC connectors would probably be preferred.


    Mike.

  • 0

    I had considered the socket and lead approach but just don't like the fact it would mean more connections and possiblities for damage just to circumvent a regulation. On the question of GFCI sockets I am struggling to find a definitive answer as to whether the machines in question would need to be plugged into GFCI sockets in the US. The machines are used in labs and hospitals by technicians analysing tissue samples and not in patient care areas. Have read conflicting advice on the requirements for GFCIs so I guess it might be prudent to assume worst case and try and source some. Excuse for a holiday to the States  maybe. Thanks for the advice by the way this is my first ever post on any forum of any kind and I was a little nervous.

    James

  • 0 in reply to James Doolin
    James Doolin said:
    Thanks for the advice by the way this is my first ever post on any forum of any kind and I was a little nervous.

    Welcome indeed to this wonderful forum. Do stick around and join in. :-)

  • 0 in reply to James Doolin

    no need to be nervous - just don't expect us to all agree with each other ;-) I've said it before but not recently, the advice on here is to be treated at a comparable level to chatting to a group of fellow electrical types in the pub - so some topic drift and silly answers are quite possible.

    Note that over time the NEC has moved in the direction of more GFCI and AFCI  rather than less, much like RCDs here, so having one or two of each sort of socket on the test rig is probably sensible future proofing, even if not yet mandatory.

    Mike.

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