gkenyon 

What about one of these down on the farm when appropriate, but not actually a requirement?

www.modernsignsdigital.co.uk/danger-480-volts.html

480 V TPN, or centre-tap single-phase, or 2-phase etc., would be in excess of 230 V to earth ... so if it's on the relevant equipment, Reg 514.10 would be OK for that ... alternatively, as I said, a Health & Safety Risk Assessment might have required it.

However, I don't think the particular sign you have illustrated here meets the requirements of the UK standards for safety signs (Red is a prohibition colour or fire safety colour, not warning, and the 480 V ought to be on a yellow background). It therefore does not meet Regulation 514.9.2, and arguably also the requirements of the Health & Safety (Signs and Signals) Regulations.

The web-site itself provides an explanation of why it doesn't meet UK requirements - it's a USA warning signs to ANSI Z535.4

Right sign, wrong format?

Right sign, wrong format?

That sign , or an UK styled version of it, might be more or less OK for a split single phase supply 230-0-230 common on farms where the DNO bottled at the expense of bringing the 3rd HV wire the last 10km or so. But actually (if we think we should or not) we are not in the habit of labeling low voltage installations except those that are unusual in some way. We all expect 230 (well 200 to 250 ish measured ) relative to earth and only normally make a note when it isn't - for example 400/690  or 690/1k2. That said we have a box here with "Danger 12V" on  it which makes me chuckle. It's not even high current...

M.

Well and truly off the subject.

As @perspicuous would point out it is declared as 240-0-240 volts, so is an oddity, but common on his jobs.

Agreed, if it's 240 V nominal to Earth, then the sign is appropriate, otherwise if it's 230 V nominal to Earth then the sign  is not needed to comply with the requirements of BS 7671,.

BUT ... if it's 230 V nominal to Earth, surely that's 460 V and not 480 V ??????