Went to do a job at one of my customers I have replaced the con unit for in recent years.
Went to do small job and isolated con unit while I rearranged a couple of MCBs to fit an RCBO.
By pure luck, I decided to have a brew and was casually looking at the great job the gardener had done to the back and noticed 16 solar PV panels on the garage.
At which point my stomach got a very heavy feeling.I spoke to the customer who said the power was routed from the garage into the house via the isolator for the garage and back to the garage MCB on the con unit which also fed power back to the grid and made meter run backwards..There was no stickers or warning about this install.

I dont know alot about PV but I was at risk of a shock even though con unit was isolated...am I right or wrong opinions please.

Since this episode,I have asked each customer do they have PV and I have come across 2 more of which only one was indicated at the con unit.
Regards
Antric

Then report them, if you wish to!

When you throw the main switch the inverter should shut down. Where are the PV isolators situated?

Andy

In the garage itself.
The customer was annoyed himself after I explained the situation and he has been on to them and put a complaint in.

Grid tie inverters as used with PV modules are required to shut down in a fraction of a second if the grid connection is lost.
There is therefore no danger in working on a consumers installation with such an inverter, provided that the installation is isolated in the usuall way.
No additional isolation of the inverter is required.

Some might consider it prudent to isolate the inverter, or the PV input into the inverter, in addition, but there is no need to so do.

Are you saying that if I spent £15000 on having solar panels installed, if the power goes off (not unknown in my part of the home counties), then it's not a lot of good to me.

-------------------------
Norman

yep

Similarly for a windmill in your back yard, if you have no wind. Whatever happened to those B & Q specials?

Regards

Any G83 compliant solar installation must have a lockable isolator to isolate it from the existing installation. While the inverter is supposed to shut down on loss of supply, I wouldn't want to rely on it.

It sounds like the installer may have fitted the isolator in the garage where it hooked into an existing garage supply, but it sounds pretty poor not to have placed an appropriate notice at the consumer unit.

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S P Barker BSc PhD MIET

Yes. Grid tied PV does not normally provide any form of backup or standby power.

That is not quite what G.83 says. If the inverter is able to withstand the reconnection of the supply when it is 180 degrees out of phase from the inverters output, then it is allowed up to five seconds to shut down following the loss of the public electricity supply.

Regards,

Alan.

And even then it's down to relying on the electronics working properly - not something to reply on for isolation & safe working!
- Andy.

Please may I ask a question? I'm NOT an electrical engineer nor an electrician.
I understand your reasons for concern and I fully understand why an "assist" solar PV installation stops feeding into the Grid the moment there is a power cut.
However it does seem to me that one of the potential advantages of a solar PV system would be the ability to supply electricity to the house in the event of a power cut. Is it possible for a system to be installed in such a way that - should there be a power cut - the system would automatically switch over to supply electricity directly to the house rather than being connected to the grid?
And if that were possible I can see that you would need a safety system to ensure that the generation could be cut off if the system required maintenance.
If such a safety system were possible and you could switch over to supplying power to the house directly - how would I get my solar PV system modified to do this - what would the cost be -and who could I ask to do that modification?

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Agnes Segal

Inverters do not shut down in a fraction of a second, in most cases they do shut down in less than 40ms.

Lashing PV equipent into sub circuits and final ring mains may be compliant with DECC G83 regulations.

But it is not compliant with BS7671, which you have to comply with to gain excemption from the ESQR regulations.

Yet again regulations have been adapted to commercial advantage or was it just lack of Competence?

Hi Agnes, I don't deal with solarPV myself, but as I understand I don't think the associated inverter would really be suitable for supplying electric to a house in a stand-by capacity - the output is too variable (in the UK anyway! ) ie, you might be able to use certain appliances whist the sun is shining but if a cloud passes over everything will stop. I'd imagine that to use the solar power available in a power cut with any usefullness you would need to consider using the inverter to charge some kind of battery system to act as a resevoir probably with another inverter to supply the electric back into the installation, then a system of change over switches and perhaps relays would be needed to keep everything safe.

I'm pretty sure the solar pv could be used when there is a power cut using the above method but the cost could vary considerably depending on your actual power requirements in the event of a power cut and how automated you would like the system to be.

Thank you to you both. These answers have been most helpful and I now understand.

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Agnes Segal

Agree with the OP's caution.

The PV market seems to be overtaken by the double glazing boys both in terms of sales and also the quality (?) of the installation. Standards are poor as you'd expect from a roofer trying to do anything electrical.

Most installations I see have grossly inadequate labelling. Often I see PV lashed into existing CU's - often with two lighting circuits moved onto one MCB to free up one for the PV - not that they have bothered to label it.

General installation standards are very poor - but then if they are assessed by the same people that do the Part P assessments what can we expect.

As for relying on a doubtless Chinese made inverter shutting down I'd rather not.



Surely 40mS is a fraction of a second - one twenty fifth of a second.

Alan is quite right, G83 requires the inverter to shut down within 5 seconds on loss of grid supply. There is supposed to be a DC disconnector and an AC isolator next to the inverter and if the inverter is not adjacent to the CU there should be a second AC isolator next to the CU. Naturally, there should be sticky labels everywhere! Sounds like the voluminous MCS paperwork has been the usual unqualified success, not a cowboy in sight eh?!

So at the "end of the day" is solar power just some "mains" type electric supply that feeds into rather than out of a consumer unit via a fuseway at the consumer unit?

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Solar power, like wind power, is an unreliable, inefficient and expensive way of supplying electricity. Which is why, until our barmy governments started throwing money about, that it was only used on space shuttles and remote locations where there was no alternative. I think the UK produces less than 2% of the world's CO2 emissions and yet we have, at huge cost, signed up to reduce these emissions by 40%. That's 40% of 2%. China's emissions of CO2 are growing at more than 2% pa. Who are these guys in suits?
Nurse, nurse, where's my medication?
So to answer Ebee, solar installations have to shut down on loss of grid supply otherwise the poor linesmen would get a belt every time the clouds moved away.