Down to Earth

[Mrjmegson]

Hey guys,

Another question, you may have guessed it from the title.

I've watched a few solar install videos, and I've seen people earthing the mounting system, which to me, makes sense to do so, but an article I've read, (http://www.geosolar.org.uk/DC earthing.html) sounds like we don't do it in this country.

I have to be honest, the article lost me (doesn't take much), but it left me not knowing what to do.

I've bought cable to earth the racking, and am more than willing and prepared to do so.

Can someone explain this article in layman's terms so I, and hopefully others can understand it.

Cheers

 

[ruggedscot]

Okay - earthing - its a complex area - You mentioned earthing the frame - not bad idea actually - Id put good bonding between all the metal work making up your metal work for support and not part of the electrical system ie not a circuit conductor. bring this together and then take it to an earth rod. I would not connect this to your house earth. The reason behind that is that if your house electrical supply has a fault then you could end up with mains voltage on your earth. A PME fault. can explain this further if required, but basically what it means is if the neutral to your house is broken then the earth may become charged to mains voltage, and anything connected to that may then be live. and if you touch it will grounded to real muddy earth yourself you could get a shock.
Id treat it light a lighting conductor and bond all that support frame together and bring it down on an earth tape to a rod. id also look at surge arrestors on your + and - to your invertor. And id be using proper fully rated solar cable.

earthing your negative lead can cause issues - the reason being that if the mains side is grounded, which in an electrical system the neutral is usually grounded and then you ground the -ve lead you may introduce circulating currents. you need to be sure that the invertor can run with ac neutral grounded and the -ve dc grounded.

 

[binky]

There is only a requirement to earth the frame on the roof if using AC micro-inverters under the panels. That could be achieved by bonding to the circuit on the roof rather than dropping an earth down to a rod on the ground. Some installers have taken to adding earth bonds to aid testing for DC leakage faults in the event of issues on the roof, but I'm not convinced that is really required and I'm not convinced that introducing DC faults to any earth system is a good idea. Of the thousands of solar systems I've encountered, bonding the frame has not been done, and I'm not aware of anything in the MCS standards that requires it, although it's fair to say I haven't read those for about 4 years since leaving the scheme

 

[Mrjmegson]

Hi guys,

Thanks for your replies, as always they are very much appreciated.

So I bought 5 core SWA for no reason then, could have just bought 4 core.

Thanks again.