earthing panel frames

andy t

What size earth cable should I use from the panels etc to the earth buss bar in my combiner box ,and on from there to the earthing rod?
And also should I be using stainless self tapping screws to attach the earth cable to the frames? If so again what size?

Im in the uk so cable is in mm not awg. Have seen 1.5mm, 2.5mm, 4mm, 6mm, 10mm, 16mm and up.

Thanks andy

BB.

Re: earthing panel frames

In my non-professional opinion, I would suggest 6 AWG minimum (4.11 mm or 13.29 mm^2).

Also, I would run the ground wire from the frame to a ground rod at the base of the installation (short, straight wiring, if bends, use large diameter bends--something like 1/2 meter or larger diameter--Sharp bends can cause lighting to jump/leave at bends).

If the run from the array is long (say much over ~3 meters), put a ground rod at the array, and another ground rod where it enters the home/building (or use the building ground rod if close by).

And, run the ground wire from the frames to the ground rod first, then into the grounding of the charge controller/battery bank (you want the lightning to go into ground rod first, not into the building/electronics first).

If you have multiple ground rods, I would suggest connecting them together with a common ground wire (rod to rod). Although, you can argue that it is not an actual requirement (in terms of lightning safety).

-Bill

zoneblue

Re: earthing panel frames

Be thorough in how you fix the wire to the frame. With the inevitable disimilar metals there you have real potential for corosion issues. Also, daisy chain is generally is not a good idea except where the wire is unbroken ( naws sell these cute little stainless screw fittings just for this purpose.) Otherwise one wire per panel, all stainless hardware, and decent tinned crimps, sprayed generously with noalox or similar. Also there should be a toothed washer next to the aluminium.

peakbagger

Re: earthing panel frames

Look up lay in ground lugs, they are expensive but are designed to tie the ground wire into the frame

Vic

Re: earthing panel frames

andy,

YES, you should use a Lay-In Lug -- WEEB:

http://www.solar-electric.com/installation-parts-and-equipment/wiring-cables-and-connectors/teluwiha/gbdbtsopagrl.html

Different parts of the world will have different exact requirements for earthing.

But, you would normally use a bare copper solid wire. In the US, normally it would #6 AWG.

The Lay-In lug would be BOLTED to the PV frame, at one of the manufacturer-specified locations, using a Stainless bolt, nut, and Star Lockwasher (for example). If your installation will need Inspection, the Authority that governs this inspection will have specific requirements for exactly what needs to be done, and probably exactly just how to route the earth cable and what is done with it at the ground level and where else it might need to go.

Will not mention exactly what we do here, as it will certainly trigger another Grounding (Earthing) discussion.

Good Luck, Vic