Solar Flexible steel conduit as mechanical protection

[Borneo]

Hello I’m new to the forum (posting on it anyway). I could do with some advice...

Over the last 2 years I have been subcontracted (labour only) to commission solar PV systems. Often these are newbuild properties and when I get there the panels are already on and the DC cabling done.

About half the time the inverter is downstairs next to the CU and so the DC cabling is routed in the plasterboard stud walls in flexible steel conduit and clipped every 40 cm. In some places this cable run is within 50 mm of the surface of the finished wall.

The main contractor who is responsible for selecting and specifying this conduit was under the impression that it was sufficient mechanical protection as per reg 522.6.204 (iv) but I think this is wrong.

I have mocked up the situation and done my own rudimentary test. The conduit deflects away from a nail or screw in between clips, but if it happens where the clip is, or where the conduit is otherwise held, then on the nail or screw will easily pass through.

So my questions are -
What are the risks from the DC cabling?
What would happen if someone did put a screw or nail into one of the string cables?
What would happen if they hit both?

 

[James]

i would not consider flexible conduit to be suitable for that purpose.

 

[Vortigern]

I think the particular reg also says "although this may not be practically acheivable" i.e. steel covering will not effectively ensure protection. I think that is a fact in the real world. What I would say is, it is better than just the wire on it's own. If you find it is not adequate and does not meet regs, what will the remedy be according to regs. There is no such remedy in the regs so it is a difficult one to follow through on.

 

[Borneo]

Thanks for the replies so far

I agree that it is not suitable James and Vortigern I think DC cabling hidden in the building fabric is best avoided ( ie should be run on the surface thus avoiding the issue altogether)

Does anyone have any knowledge as to the second part?

What would happen if one cable does get pierced by a nail, screw or drill?

What about if both do?

 

[suffolkspark]

I'm assuming its not run in zones either? I've only to date come across PV that's had its DC cables surface myself

 

[Sensei]

Thanks for the replies so far

I agree that it is not suitable James and Vortigern I think DC cabling hidden in the building fabric is best avoided ( ie should be run on the surface thus avoiding the issue altogether)

Does anyone have any knowledge as to the second part?

What would happen if one cable does get pierced by a nail, screw or drill?

What about if both do?

HI, I've attached a picture from the IET code of practice that best covers what you're asking. Simon