info on earthing the pv frame

stubo300 · Mar 14, 2011

i have read the dti and just need some one to explain it to me abit better please.

if i install a 3.60 kw system on a single story roof do i need to earth the frame work, if so how do i earth it, do i take it back to the main pme earth or do i have to run a seperate earth to a earth rod

BruceB · Mar 15, 2011

Have you been through the decision tree on page 23 of the guide. That will give you the answer. If you do not understand a particular question or do not know a particular answer then tell us what it is and we may be able to help. Not enough info yet.

Regards
Bruce

Markc · Mar 15, 2011

Are you using a transformerless inverter? If yes then earth bond array. If no then don't earth bond array.

If using a Transformerless inverter you MUST install a Class B RCD (standard split load or 30mA RCDs are NOT class B) as well as earth bond array.

If using TL inverter and the earthing arrangement to the property is TNCS then the array but be earthed via a earth electrode (earth Stake)

If the earthing arrangement is anything else other than TNCS then the earth bond cable goes back to the MET terminal.

To earth bond array attach 10mm earth cable between rails (so linking all rails together).

Mark.W · Mar 15, 2011

Hi Markc

That's pretty good info there!

Is that written down somewhere that I can show my boss?

Cheers
Mark

Markc · Mar 15, 2011

Hows This?

From the DTI guide

stubo300 · Mar 15, 2011

many thanks guys

Mark.W · Mar 16, 2011

Markc said:
Hows This?

From the DTI guide

Thanks Markc, I should have been a bit more clear, I wanted to know more about bonding the rails!

M

dansk · Mar 16, 2011

Im still really struggling with the Class B RCD thing - Some of the TL invertors have a built "Class B RCMU" "residiual current monitering unit" built to standard EN 50178 - so surly "by design" the inverter isnt able to inject DC into the AC? and therefore mitigate the need for a Class B -

BruceB · Mar 16, 2011

Yes that is what the SMA documentation (posted here a few times) claims and hence their TL inverters fall into the exception case of the regulations and do not need a type B rcd
Regards
Bruce

dansk · Mar 16, 2011

Ok - i thought that was the case - i dont use SMA, but these inverters still have the RCMU built in.

Next question - if its TL - then the array will still need bonding? and if its TN-C-S it will require a spike?

JulianC · Mar 16, 2011

dansk said:
Ok - i thought that was the case - i dont use SMA, but these inverters still have the RCMU built in.

Next question - if its TL - then the array will still need bonding? and if its TN-C-S it will require a spike?

Beware of assuming any inverter with a built in RCMU is not capable of dumping DC onto the grid in the event of a fault. This may well be the case, but unless it's certified to the relevant BS/EN thingy (I forget which one) I don't think you can fit it without a separate class B RCD. As far as I am aware, only SMA transformerless inverters meet the required standard in this respect.

And yes, if it's TL, the array will still need bonding.

dansk · Mar 16, 2011

JulianC said:
Beware of assuming any inverter with a built in RCMU is not capable of dumping DC onto the grid in the event of a fault. This may well be the case, but unless it's certified to the relevant BS/EN thingy (I forget which one) I don't think you can fit it without a separate class B RCD. As far as I am aware, only SMA transformerless inverters meet the required standard in this respect.

And yes, if it's TL, the array will still need bonding.

Yes point taken - im confident these comply.

Regards to a spike - do you have to do a Ze on the spike? and how do you install them? just smack them into the ground were the 10mm comes down the wall?

Markc · Mar 16, 2011

dansk said:
Im still really struggling with the Class B RCD thing - Some of the TL invertors have a built "Class B RCMU" "residiual current monitering unit" built to standard EN 50178 - so surly "by design" the inverter isnt able to inject DC into the AC? and therefore mitigate the need for a Class B -

If you are refering to the Fronius range the RCMU does NOT meet the Class B requirements, Horses mouth from Fronius at Eco Build and again from our suppliers.

dansk · Mar 16, 2011

No im not - after reading further into it maybe they dont, its something to do with a perticuler reg VDE0100-712, were can i get a copy of that to read?

Can i ask you - If i install a seperate 2 way CU, do i need a class b 16A RCBO? or 63A class b incomer with a normal 16A mcb?

Markc · Mar 16, 2011

dansk said:
No im not - after reading further into it maybe they dont, its something to do with a perticuler reg VDE0100-712, were can i get a copy of that to read?

Can i ask you - If i install a seperate 2 way CU, do i need a class b 16A RCBO? or 63A class b incomer with a normal 16A mcb?

Shouldn't use RCBO's as they aren't double pole from what I have read somewhere. You will not get a Class B RCBO anyway from my investigations and a Class B RCD will be 300mA. Unless anyone knows different?