Plug-in Solar supposedly going to be 'easier'?

Steve Nixon76 said:

connect solar PV panel inverter directly to the mains using a 3 pin plug and socket arrangement

Welcome to the forum.

The obvious difficulty with this idea is the plug and socket. Would you want a BS 1363 plug with 230 V between the pins?

a BS 1363 plug with 230 V between the pins
When its plugged in of course, that's normal and fine from a touch perspective, but if it adds significantly to the available current on the load side of a 32A MCB, now you have all your other loads plugged in to what is effectively a higher rated circuit than originally, but more importantly quite likely with a longer disconnection time 

I'm assuming like the hard wired units, the inverter has to curl up and stop if it detects a total loss of mains, but this may not be as fast as the supply RCD tripping on its own would have been.

I can see the attraction, and as a plug in gadget, its strictly  outside the reach of BS7671, but I agree there is scope for a few unpleasant unintended consequences.
DIY plug-in kits are  already on sale so I am not too sure what the govt is planning to change or why it thinks it has any levers to control this, as I see it, what folk hang out of a window and plug in is pretty much unenforceable.

And in the UK very few buildings have balconies, unless perhaps its a tower block, which is the very sort of place it would not be a good idea to have too much of it as all the problems of reversal of street main voltage drop and voltage rise still apply, 

Anyway, technical wisdom aside, the govt, position seems to be 'Action 2' on this long list.

https://www.gov.uk/government/publications/solar-roadmap/solar-roadmap-united-kingdom-powered-by-solar-accessible-webpage#part-2-actions-to-address-key-challenges

" Plug-in solar ^{[footnote 28]} can provide opportunities for households to adopt solar more cheaply, particularly for those in rented accommodation or flats. Currently, UK regulations do not allow plug-in solar to be used in the UK, but the government is working to explore its potential.

Action 2: Government will conduct a safety study this year with the aim of unlocking opportunities for plug-in solar over the next few years.

Alongside lower electricity bills, there are many extra benefits for householders that invest in rooftop solar. These include improved Energy Performance Certificate (EPC) scores and property valuation. ^{[footnote 29]} But barriers remain."

Personally I think it would be far more to the point to increase (deregulate) the scope of who is allowed to do a properly wired installation and perhaps see if the various processes can be streamlined a bit. This should try to encourage better engineered solutions and discourage this sort of thing by making the savings of the DIY one insignificant rather than by creating new and unenforceable rules.

Mike

PS my German colleagues tell me that the usual Balkonkraftwerk is limited to 800W per socket plugged in, but putting more than one in the same house spread across the 3 phases is "not unknown" ;-) 

Edit.

There are historical reasons we don't usually build houses like this, and I fear planning permission would be an issue.

This sort of thing might be possible on ex-council blocks.

Of course these devices will conform with the Electrical Equipment (Safety) Regulations 2016 and the Electromagnetic Compatability Regulations 2016 won't they?

What British Standards ENs will they conform with on the Declaration of Conformity?

Will they conform the to ENA Type Testing requirements to operate in parallel with the DNO supply?

How will the RCD that is hopefully on the socket circuit handle bi-directional current?

Will the inverter keep supplying the circuit when the RCD trips on a fault beyond the required disconnection time?

JP

I fear the answer to all those very valid concerns will be forgotten in the race to reduce the cost of the plug in option to the minimum. Given you can buy and plug in phone charger that is both a virulent source of interference, and lethal, for about half the price of the good one, and folk routinely do, to save a few quid, my confidence that all DIY solar installations will be full compliant is, shall we say,  not high.

Also many of the general public  do not appreciate that when you buy from Amazon/Ebay/Aliexpress/Desertcart etc and the parcel comes to your house  from abroad, you the purchaser assume the importers' responsibilities with regard to things like CE safety tests and other regulatory matters - so if there are issues, you are very much on your own. But, equally, such things are already out there, and there are not and regulatory mechanisms that are readily enforceable.

The better ones do claim to comply example. "With the user-friendly Flex-S3 Plug and Play Cable, installation is simple—just connect the micro-inverter directly to a socket with no need for complicated wiring."

That particular model can be bought as a kit with a couple of  panels and mountings for a few hundred quid.

Mike.

Humm. We did have something similar some years ago with micro wind turbines (which eventually died a death as turbine efficiency at that size is so awful they'd never repay their embedded energy).

On the other hand, things might not be quite as bad as they first appear. Once unplugged the inverter would presumably loose all earth reference, so while the L & N pins might still be live w.r.t. to each other, they'd be separated from Earth - so like a bathroom shaver socket - there'd be little risk of a conventional shock to Earth. Even a finger-to-finger shock is unlikely to be lethal if all the finders are on the same hand (it certainly hurts, I can vouch for that, but without a path across the chest the chances of ventricular fibrillation seem small.) Touching both pins with opposite hands, in order to get a shock across the chest, seems much less likely, especially if it needs to be done within the short time after unplugging it takes a modern inverter to spot the loss of mains and shutdown. Older inverters can be pretty poor on that count (my old G83 one takes several seconds) but if more modern ones could achieve that within say 1 full cycle (20ms) that would seem at least comparable to additional protection offered by 30mA RCDs.

Potential loss of overload protection of the host socket circuit might need some thought (but if the power of the panel is "small" the additional risk would also seem small - after all how often does a ring run within a few hundred watts of the MCB tripping? How often have you seen a domestic ring overload protection operate anyway?)

RCD directionality might also be a consideration (but there are likely hundreds of thousands if not millions of early PV installations wired on the load side of conventional RCDs with no noticeable piles of bodies in the streets).

   - Andy.

I agree

A commando style socket with recessed connectors would be better then a BS 1363 plug.  There are also the other factors to consider like if this is a DIY job will some of the following be checked first (Not an exhaustive list)

Is it a ring final circuit or Radial

What is the Earth and bonding at origin of install, is the CPC functional

What size cable is being used eg 2.5mm2 CSA or 4mm2 CSA

What is the cable type T&E, VIR or LS0H (Low Smoke Zero Halogen)

Is it a spur of a spur

Does the CU/DB have an MCB making it bi-directional

Does the CU/DB have an RCBO which is bi-directional

If there is a Split load board is the RCD type AC or Type A

Will sticker/label be fitted on the CU/DB and at the point of orig stating secondary source of energy

Will smoke/heat alarm be fitted in that room that is interlinked to the rest of the dwelling

Does the insurance policy for dwelling cover the inverter

Does the Solar PV / inverter have rapid shutdown

Does the Solar PV / inverter addition count as a new circuit or an addition or alteration

Should an SPD Type 2 be fitted in the CU/DB

An interesting debate so far. It cannot be beyond the wit of man to design a plug and socket arrangement which prevents contact from live conductors on both sides, either purely mechanically, or by having an interlock which opens only when the inverter has powered down.

Of course, if they really are intended for balconies, it assumes that there is a socket on the balcony. Failing that, do you trail the cable in through a door, which being ajar, lets all the warm air out and defeats the purpose? Not today, thank you very much!

Now then, do you need to get a pass on an EICR before an MCS contractor will fit solar PV? If not, how do they ensure that the installation is fit to take PV?

The one thing which seems obvious is that these 'balcony' systems are easier than conventional roof systems. Although a limit of 800 W may not be much, it could be a significant proportion of a small flat's consumption and I like the idea that a tenant can take the system with them on moving house.

Leaving aside safety issues, what do you do when you want to sit out on your balcony? Fold them away? Their use must be limited on east and west sides of a building where they will be in shade most of the time, and no use at all on the north side.

BS 7671 does not concern itself with product standards for equipment that may be plugged in to socket outlets.

If the government ae so keen on these devices no doubt they will commission a product standard for devices being placed on the UK market that protects the public, livestock and property.

I do not believe that currently there is a product standard for these devices?

JP

>Is it a ring final circuit or Radial
Nobody will care.
>What is the Earth and bonding at origin of install, is the CPC functional
It should be, because if it isn't, the entire installation is already unsafe.
>What size cable is being used eg 2.5mm2 CSA or 4mm2 CSA
Nobody will care.
>What is the cable type T&E, VIR or LS0H (Low Smoke Zero Halogen)
Nobody will care.
>Is it a spur of a spur
It shouldn't be, but nobody will care.
>Does the CU/DB have an MCB making it bi-directional
Nobody will care.
>Does the CU/DB have an RCBO which is bi-directional
Nobody will care.
>If there is a Split load board is the RCD type AC or Type A
Nobody will care.
>Will sticker/label be fitted on the CU/DB and at the point of orig stating secondary source of energy
No
>Will smoke/heat alarm be fitted in that room that is interlinked to the rest of the dwelling
No
>Does the insurance policy for dwelling cover the inverter
Maybe home contents will.
>Does the Solar PV / inverter have rapid shutdown
It really should do if it's plug in solar!
>Does the Solar PV / inverter addition count as a new circuit or an addition or alteration
No.
>Should an SPD Type 2 be fitted in the CU/DB
Nobody will care.

There are existing standards for time to detect loss of mains, and limit output voltages and currents that are for micro inverters that might as well apply as they are.

Generally the govt does not 'commision a standard' rather manufacturers decide the generic standard is too hard for their type of product, and try and push through a dedicated one that is suitably shaped.

Mike.