Aren't they IT supplies - completely un-grounded on the AC and DC sides?  In which case, it's not much different from a small petrol generator.

In theory, you could touch one of the live outputs and not be electrocuted, because there's no current path through ground.  Which means and RCD wouldn't make much difference.

Thanks Simon, this is DC battery , inverted to AC out        , however 551.4.4.2 has an RCD being required on TN,TT and IT on final circuits..... but then goes on to say the RCD would only work in IT if fault was on the supply side which could occur when being charged ?

The ones I have seen advertised all charge on DC only.  That could be a mains adaptor, car charger or solar panels.  Where would the RCD go in that?

Separated or floating source for Class II or equivalent isn't really a bad thing. Issue being that not all appliances are fully Class II ... and floating supplies are not really suitable for multiple Class I products, or the type of products that have protective conductor currents as well as Class II approach.

Not all inverters lack separation between input and output, though - some have  isolation between each of DC input, AC input, DC output and AC output, RCDs built in at the AC output, output neutral connected to a protective conductor so the RCD works and can be connected to the vehicle or unit chassis, or a separate earth electrode or, if in a building, the MET ... so they are ready-to-go for installation (via suitable connectors) in caravans, motor homes, mobile/transportable units, and workshops.  This manufacturer is an example: https://www.claytonpower.com/

You get what you pay for.

Looking about I  presume you mean these sort of things.

https://www.hampshiregenerators.co.uk/product/generators/portable-power-stations/anker-535-powerhouse-portable-power-station/

Never used that exact make, but the comments below are general..

Personally I'd be far more worried about the fact that these can encourage the casual use of 13A sockets in the rain, which seems generally to be a regulatory blind spot for outdoor power in the UK, rather than the presence of an RCD that will never trip, as until you add an NE link there is no path to operate one. In that sense the comment that it is like a small genset is very true, as they are normally floating windings. Here there is no 50Hz transformer, but a battery operated screamer running supersonically, with a very small ferrite core, rectified to create a DC , and then some power transistors that commute the output between the DC levels to fake a sine wave from bits of square wave...

Some designs can also be an EMC nightmare - I'm not saying this one is especially but fast switching devices and hundreds of volts p-p can wreak havoc.

As regards CE/UKCA  marking, it only needs to meets the harmonised standards that apply to that product group - probably the LVD, EMC and machinery directives, and certainly not BS7671.

Mike

mapj1 said:

Some designs can also be an EMC nightmare

And regardless of EMC, there's the basic issue of whether a switched-mode converter is compatible with a switched-mode power supply or a switched-mode power controller (e.g. VSD) ... perhaps another avenue that standards ought to have explored well before now to ensure compatibility ?

The incompatibility should certainly be more widely published. Inverters are very different to mains, in waveform and in over-current performance, and as you say the behaviour on a negative resistance load (i.e. where current goes up as voltage falls, unlike a 'normal' positive resistance where current and voltage rise and fall together) like an SMPS can be quite exciting.

A large part of the advantage of switching designs at least in the portable kind, is the small size and light weight, and that does mean not being able to store much energy in large capacitors and inductors, so I do not think you can mandate that inverters should all behave like inertial gensets, but to require makers to be honest about their waveforms and clear about earthing or lack of it would be a very good start.

Something similar requiring labels on dimmers and LEDs would be good too. - trailing edge, leading edge, pure sine and switched capacitor dimmers are all uniquely incompatible with some designs of light...

But for me the thing that I see giving the most problems, in terms of damage and 'tingles' is the use of 13A sockets, that are really an indoor beast, and only scarcely  up to 13A in many designs, in places with rain and splashing, where something more like the old BS4343 would be far better - perhaps a shuttered version of that is needed.

Mike

Aren't they IT supplies

I'd say no - just separated. The point being that exposed-conductive-parts are left floating rather than being specifically connected to Earth (there's not T to make it IT). BS 7671 won't be in scope, but if it was it'd be covered by sections 413 (for a single appliance) for 418.3 (for multiple appliances) - and then there'd be no 30mA RCD requirement at all.

   - Andy.

Thanks Andy, that's exactly what I'm after !