Tail sizes from PV sub-board

[Leesparkykent]

If there are spare ways why are you not connecting direct to the dist board.

I’ve seen many installed this way that do not comply.

 

[Ian1981]

Or if you apply 434.2.1

Installed in galv trunking perhaps as one method?

 

[davesparks]

Installed in galv trunking perhaps as one method?

Yes, or plastic trunking, properly clipped/restrained depending on the exact location and environment.

 

[davesparks]

To prevent the chances nuisance tripping the main board.

Tripping what and how?

Ok thanks, that makes a bit of sense. The pv board houses an rcbo for the pv and will have a din mounted generation meter. It will have no spare ways.

Is there a main switch in the board?

 

[westward10]

You must have some design criteria for this want of a better words, lash up.

 

[westward10]

To prevent the chances nuisance tripping the main board.

If you are worried your new install is likely to cause nuisance tripping then you need to reassess what you are doing as the best method is to install directly to the existing dist board providing there are spare ways.

 

[Leesparkykent]

If you are worried your new install is likely to cause nuisance tripping then you need to reassess what you are doing as the best method is to install directly to the existing dist board providing there are spare ways.

I wouldnt say it’s the best way if there is spare way on a RCD protected way that shares the same side as a socket circuit for example. It would actually be non compliant due to how long the inverter takes to shut down which can be up to 5 seconds under G83.

 

[Octopus]

If you are worried your new install is likely to cause nuisance tripping then you need to reassess what you are doing as the best method is to install directly to the existing dist board providing there are spare ways.

That's VERY wrong for the reason Lee gave above ........... but is the most common method of install I see ......

 

[CBR600]

Just a quick thanks to everyone for the contributions on this last night. All very helpful.

 

[westward10]

I wouldnt say it’s the best way if there is spare way on a RCD protected way that shares the same side as a socket circuit for example. It would actually be non compliant due to how long the inverter takes to shut down which can be up to 5 seconds under G83.

Where does it state this would be non compliant, not had much to do with these systems so would be interested.

 

[Wilko]

I wouldnt say it’s the best way if there is spare way on a RCD protected way that shares the same side as a socket circuit for example. It would actually be non compliant due to how long the inverter takes to shut down which can be up to 5 seconds under G83.

Learning every day.
If I've understood correctly - in a dual RCD board if they've attached PV invertor to MCB under one of the RCDs, if that RCD detects a fault and trips, great. But the invertor continues to put 230V onto the common MCB busbar. So ADS has not been achieved (!!!).

 

[davesparks]

Where does it state this would be non compliant, not had much to do with these systems so would be interested.

I can’t give a regulation, but plain old common sense should be enough.
If a person receives a shock the RCD will trip, but the PV will continue to supply power to all circuits supplied by that RCD for a period of time, therefore defeating the purpose of the RCD and killing the person.

 

[westward10]

I can see the sense of it now I just wondered if this is quoted anywhere.

 

[Ian1981]

Regulation 712.411.3.2.1.1 states that on the ac side the pv cable shall be connected to the supply side of a OCPD for automatic disconnection of circuits supplying current carrying equipment

 

[SibertSolar]

Nuisance tripping "might" be a problem when sharing an RCD, but that's the least of the potential issues. More likely (when using transformerless inverters) is that the Type-AC RCD (usually fitted in residential CUs) might become saturated and never trip under fault conditions. That's in addition to the scenario outlined by others relating to the shutdown times of PV inverters and ADS intention of the primary RCD in the first place.....amazing that this topic still causes discussion so many years down the line!! As for the OP's original question, using 10mm2 tails from henley blocks broken into the meter tails (25mm2) is perfectly fine so long as the OCPD on the PV connection is suitably rated. In fact, I'd go so far as to say this is a better method that using a spare way on the non-RCD protected side of the main CU (various reasons including ease of monitoring and avoiding potential issues with RCDs....)

Just my tuppence...