Where I work,we would not normally test a rack to BS7671 unless it contained something that was essentially fixed wiring. We would however treat it like an appliance,or an extension lead and many appliances depending on the internal configuration.

Mike

Hi Mike,

Thank you for your quick and helpful reply. I don't believe any part of this will be like fixed wiring, though I did wonder about PLCs and things that have the power cores wired to individual terminals rather than being in a single IEC power cable. The power terminals themselves I understand to be under LVD scope and therefore covered by UKCA marking, however beyond that I was wondering about wire sheath colours and if ground connection rules might differ between the UK and USA.

Will

Is the rack expecting single or 3 phase supply?

Easiest is to have a bs4343/en60309 incomer if you can, and then define the supply requirements - eg 32A single phase or 16A 3 phase or whatever and  the overload and cable protection becomes the responsibility of the customer,

In simple situations it is often easier to buy in ready made block and bolt it in if you are not tooled up for making it. LVD will set requirements on IP rating, creepage and clearances.(Companies like this make a living selling ready wired cables and making unusual distribution blocks to order if a normal extension will not do.)

Single phase UK colours for wiring are Brown (live 230V to ground) Blue (neutral - almost 0V to ground) and Green/yellow (earth - what we call what you call ground ...)

Wiring should survive a 500V DC test between L+N to earth and manage and have an impedance of many megohms, probably hundreds of megs when new.

Reduced test voltages if surge arresting components are fitted and cannot be isolated during testing.

It would be easiest to use UK mains lead to make up internal wiring. At the least the devices with their leads attached, should then be tested to a level equivalent to a PAT (earth continuity, insulation of supply conductors from earth when dead, and leakage current and total power consumption when switched on).

If the components in the rack are already CE marked then there is a large part of the work done.

If you are adding earth studs to the rack, then I suggest to go for M6 threads- it meets everyone's requirements I caution that the American use of something in a UNC that we cannot get a replacement nut for that is under 4mm diameter does not impress UK eyes !

Mike.

It will receive a single phase supply. Thanks for the suggestions, especially on the earthing studs! I'll pass those on.

Single phase makes it very easy. Your easiest choice  now reduces to 32A blue plug, or 16A blue plug.

Watch total capacitance to earth if you have lots of kit with built in mains filters - it is likely that the users will want to supply it via a 30mA RCD (==  GFI) and the out of balance current that flows with 230V between L and E will be proportionally larger than 110V designers are used to.

Don't go above 10mA of total earth leakage or the wheels can start to come off in terms of false alarm tripping - as well as making a lost earth first fault to an immediate  danger condition.

Mike

(In general we like metric nuts - spares are available in every hardware shop. Things that use funny threads that have to be ordered off the internet and flown in and arrive a week late are a pain in the bottom .. The other happy alternative is to find a few spare screws and nuts in a bag in the back of the box).

Single phase makes it very easy. Your easiest choice  now reduces to 32A blue plug, or 16A blue plug.

Watch total capacitance to earth if you have lots of kit with built in mains filters - it is likely that the users will want to supply it via a 30mA RCD (==  GFI) and the out of balance current that flows with 230V between L and E will be proportionally larger than 110V designers are used to.

Don't go above 10mA of total earth leakage or the wheels can start to come off in terms of false alarm tripping - as well as making a lost earth first fault to an immediate  danger condition.

Mike

(In general we like metric nuts - spares are available in every hardware shop. Things that use funny threads that have to be ordered off the internet and flown in and arrive a week late are a pain in the bottom .. The other happy alternative is to find a few spare screws and nuts in a bag in the back of the box).

Hi Mike,

Very helpful again, thanks. Are plugs typically provided on cabinets like this? I was expecting a fixed wiring installation directly into the cabinet would be acceptable, though I will certainly confirm with the host first.

Good tips on the capacitance, earth leakage and earthing nuts thanks. I also prefer metric, though I believe this is unusual in the USA.

Will

You do not have to connect via plug and socket, but racks that may need to be isolated to be worked on or pulled out to be got behind very commonly are. Data centres seem to be full of connectors like that. It also makes it easy for the local sparks to decide where his work stops - make socket on wall live, run usual BS7671  polarity and earth impedance checks and  then pack tools away and go for an early lunch - that way the power is ready in advance when the rack arrives.

It also avoids having to wait and then argue the toss about who is terminating the interlinking cable and if the rack needs testing as part of the fixed wiring - which of course  is where we came in.

At least over here those connectors are cheap as chips compared to labour, and do make testing and isolation to prove dead particularly easy.

But do check with your customer - their local chaps will have their local preferred method.

Mike.

Thanks again Mike, invaluable advice. Certainly, avoiding any question as to whether the cabinet is part of the fixed wiring is a good enough reason alone.