PV cabling and earth

[soltek]

I am just completing my first install for my forthcoming MCS assessment. It is a 690w system.

1. Am I ok to run the cable on the AC side of the inverter in 2.5mm cable (as it is only 690w system)?

2. I need to earth the array as it can be touched from a velux window. What cable size for the earth? ( I take it that it needs to go back to the ccu)

Many thanks

 

[SolarCity]

1. Possibly. Depends on the length of the run of the cable. You're allowed 1% volt drop.

2. Usually 10mm. And back to the main earth UNLESS you are on a PME system. Which means it needs to be run to a seperate earth rod.

 

[malcolmsanford]

Being a Non PV installer I was wondering what you are earthing .................. aren't the panels class II

 

[SolarCity]

He is talking about bonding the array rather than running a CPC.

 

[malcolmsanford]

Isn't the array frame floating?? and why would you bond it ?

 

[SolarCity]

If it's reachable from a velux window then it could be argued that it would be safer to bond it. I think a pretty good argument could be made for it not being bonded as well.

 

[malcolmsanford]

To be honest I think unless your worried about lighting strikes ....................why would you bond it. If there was a fault developed on the class II panels, how would that induce a fault onto the frame.

I can understand if it was ground mounted you would think about it, espicially if you had AC circuits around ...........but floating free on a roof not sure why.

 

[SolarCity]

Well it can be reached from the window, so this does have to be a factor in deciding if it should be incorporated into the equipotential zone.

 

[malcolmsanford]

Is it likely to introduce a potential and therefore be classed as an extraneous conductive part? Before I started bonding I think I would test to see if it was.

 

[yellowvanman]

Leave floating if all the following are met:
Class II modules
Class II cables and connectors/JBs etc.
Isolation transformer in inverter.

 

[soltek]

Thanks guys for all your advice. I note from a recent similar thread started by cookiemonster that he too wasnt sure about bonding (he was using the same inverter - Soladin 600).

Matt_M cleared it up in the end by telling he was advised to bond regardless as the Soladin has a galvanic transformer which lets an AC voltage onto the DC side.

Although the modules cables and connectors are class II there is no isolating transformer.

So bonding it is then - at least I have 3 weeks before my assessment t do it!