Installing US socket outlets to a commercial office space in the UK

Question

Morning Everyone, 
 
 I would like some advice on the following please. 
 
 We have been asked by a client of ours to install a number of socket outlets to power equipment imported from the USA, within a commercial office space. 
 
 I am aware that we will need to install a step down transformer and increase the frequency to 60Hz in order for the imported equipment to operate safely and correctly. 
 
 Can anyone advise how we stand from a regulatory point of view? Will the installation after the step down transformer be regulated under BS:7671? Will we need to install 30mA additional protection to to these sockets (lower voltage - 110V site supplies do not require this?) Do we need to use a specific type of outlet? - I am aware of non-shuttered and shuttered outlets available. 
 
 Any advice is appreciated thank you.

mapj1 · Accepted Answer

Changing frequency is not very practical at anything other than very low powers. Conversion to DC and then inverting, or in old school method, for lots of power, motor-generators are the only sensible ways. 
 What sort of loads are they intending to connect ? most office electronics does not care about 50Hz or 60Hz, and probably does not care about 110V very much either- things like laptops and monitors and printers etc are universal mains these days. Anything big like a heater would be better to buy one over here. 
 A US voltage UPS may be a way forward if there is some bespoke kit that really must, but I'd be pushing back. 
 UK 110V building site supplies are center earthed while US 100V has one side as neutral so the possible shock to ground is doubled. I think some RCD would be needed - but then the Americans have GFCI that are more or less the same thing. 
 
 From an installation perspective unless the building is owned outright, you probably want anything you do to be more like an appliance or a rack and some extensions rather than full blown fixed wiring. 
 Things like US airbases and embassies in UK and mainland Europe have US style supplies, but they are not properly under local law. Certainly when I was last on a US airbase, and that was in the last century, they had their own 60Hz generators for the site und once inside the armed guards all installation was to US code. 
 I suspect a normal UK office does not enjoy that freedom- or budget. 
 Mike

AJJewsbury · Answer

Will the installation after the step down transformer be regulated under BS:7671? 
 
 In BS 7671 terms, yes - it covers electrical installations generally unless displaced by a more specific standard. I suppose there is a question of whether you need to adhere to BS 7671 - or whether another standard would be more appropriate (e.g. the US's NFPA 70). That would have to be answered in conjunction with the likes of the Safety duty holder and the likes of insurance providers. 
 In principle there's nothing in BS 7671 stopping you using 110V sockets - mostly the same requirements as any other LV socket circuit would apply - although some of the details (e.g. table 55.1) are likely to pose some challenges - but they might be circumventable with a bit of imagination, I can certainly see an argument that danger might arise from plugging a 110V appliance into a 230V circuit for example. 
 - Andy.

Installing US socket outlets to a commercial office space in the UK

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