Ed Throws Trade Bodies Into Chaos Over DIY Solar!

psychicwarrior said:

Cue another early amendment and Section in BS7671

and 

Chris Pearson said:

On this basis, indent 1 of 551.7.2 applies, so we do not have to worry about sub-paragraph (ii) of indent 2.

and

Sergio Fernandez said:

BS7671 AMD5 does have a ring to it.  JPEL64 must be fuming

Why? It's a plug-in appliance, and not part of the electrical installation?

The essential requirements of the Electrical Equipment (Safety) Regulations apply to the product ... basically it must not cause a danger ... and the manufacturers of such products ought to take into account not just the current (or even the 'due on 15 April 2026' BS 7671), but existing installations.

psychicwarrior said:

In any case, we don’t like being forced 'poor' , whilst others get [to varying degrees] 'rich', due to some questionably argued existential threat foisted 'solutions' amongst other issues.

Again, these issues are not for consideration by JPEL/64.

However, other solutions are available, and some local authorities are very keen to help those less fortunate ... others not (or won't through political agendas) ... it's all about policies, politics and money markets at the end of the day.

There's a lot to balance, though ... if those poor 'traders' can't get rich from the oil/gas market, where else are they going to get their pound of flesh?

It seems to me these plug-in inverters (indeed many designs of grid-tied inverters in general) are somewhat different to traditional generators.

A conventional generator once started would tend to keep going (until it ran out of fuel) regardless of whether the connection to the grid supply remained or not - hence the worry about plug connection exposing live pins etc.

A grid-tied inverter on the other hand is slaved to the grid (or other primary supply) - in principle it won't supply any power should the connection to the grid be lost. In some ways it behaves more like a load than a generator - it's wired like a load (no N-PE link) and it stop if the grid stops - just like a load and unlike a conventional generator. It's just load that draws negative power in the conventional sense.

Yes there may be a short time after a grid fail when some energy is still produced - but that's not unlike some conventional loads - e.g. rotating motors that can produce back-EMF when the motor spins down, or capacitive discharge back through the supply pins (I can't be the only one old enough to remember getting jolts off CRT monitor plugs) - but we don't regard those as generators.

So how about we regard grid-tied inverters, not as generators, but a negative loads?  Most of the regulatory objections would then drop away. The -ve nature of the current would still mean we'd have to take overcurrent protection into account (Iz ≤ In + Ig equivalent sort of thing) as in principle we should be re-evaluating things when adding any load) . That approach also aligns with things like putting additional protection RCDs on the grid-end of PV AC circuits.

Just a thought. I may well be barking up the wrong tree (again), but I think it would help at least to treat these things as fundamentally different to conventional generators and not lump them in with a stack of assumptions that really don't apply.

    - Andy.

AJJewsbury said:

Just a thought. I may well be barking up the wrong tree (again), but I think it would help at least to treat these things as fundamentally different to conventional generators and not lump them in with a stack of assumptions that really don't apply.

I'm not saying this view is wrong ... BUT ... there are other causes of 'danger' than live plug pins (whether or not you subscribe to that as an issue) including:

• 'blinding' Type AC RCDs.
• protection against overload for final circuit conductors that was not envisaged by the designer of the electrical installation (and hence dangerous overheating ... possibly fire) according to BS 7671 / IEC 60364 / HD 60364

I'm not at all stating any probability of any of these issues ... unfortunately, they are issues to be considered in the round, and particularly in terms of the 'essential requirements' of the Electrical Equipment (Safety) Regulations.

Overall, it's a very interesting discussion.

'blinding' Type AC RCDs.

A problem that can equally occur with electronic loads in general - so not specific to grid-tied inverters.

protection against overload for final circuit conductors

Again even adding a conventional load to an existing circuit could potentially take it into the "small overload of long duration" territory that BS 7671/IEC doesn't really have an answer to.

I'm not saying these aren't problems - far from it - but I'm suggesting it might be simpler to consider them on their own rather than lumping them in with the concept of generation.

    - Andy.

'blinding' Type AC RCDs.

A problem that can equally occur with electronic loads in general - so not specific to grid-tied inverters.

protection against overload for final circuit conductors

Again even adding a conventional load to an existing circuit could potentially take it into the "small overload of long duration" territory that BS 7671/IEC doesn't really have an answer to.

I'm not saying these aren't problems - far from it - but I'm suggesting it might be simpler to consider them on their own rather than lumping them in with the concept of generation.

    - Andy.