Bonding of TL INVERTER ??????

[1973millerman]

Hi everyone,
I have my NAPIT inspection at the end of the month, currently putting a system on my roof to use for the inspection.
My question is, do i have to carry out bonding ?? as we think the DTI are possibly going to change this.
If i do need to carry out bonding, could someone explain the process please, would bonding of the rails be suitable, using a 10mm, going down to a earth rod, ( PME System on site ) i am a qualified sparks, but very new to this game
Hope someone can help
Regards 1973millerman

 

[malcolmsanford]

I do believe that the DTI as brought out a revision of it's guide and part of it is proposed amendments is concerning earthing/bonding the array, some installers think that the frame on a TL transformer is an exposed conductive part and so it should be earthed, for me if it is anything it must surely be an extraneous conductive part and therefore bonded.

As your a sparks you should know that a bonding conductor on a TNC-S system has to be 10mm if the supply cable, not the tails, is ≤35mm so that is what you need to fit.

But I gather that some of these TL transformer still afford simple separation of the AC/DC systems, I think some of the SMA ones allow this, and so you may not need to bond the frame in this case, or need to use a B type RCD

 

[1973millerman]

Thanks for the reply, so are you saying i would have to link every panel together with a earth fly lead.
I am using a SMA4000TL Transformer

 

[malcolmsanford]

Why would you earth a class II panel, for a start where is the earth going to fit to, the support brackets?

You are bonding the frame and so the 10mm will be fitted to the frame and in a TNC-S according to the DTI will then be run to it's own earth electrode.

Does the manufacturers instructions advise that you need to bond the frames, as I'm led to believe that the SMA inverters though are TL still allow separation of the DC/AC circuits.

 

[BruceB]

Millerman, You have to make an engineering judgement on this and be able to explain yourself to the assessor. The rulles are likely to change, but today they have not yet. I have seen some argue best practice is to bond every panel to every rail and every rail to each other and then to the earth spike. If you are happy that the clamped connections make sufficient electrical contact for the bonding, then no need to string green and yellow everywhere. Your inspector will know the rules are changing. Just make a decision, explain it to him and in the worst case be prepared to change it.

 

[cal]

Bond it, earth spike, if it is a tl inverter, and leave it floating if there is a transformer (without seperation ( as tl suggests)) then you must asume that there is no simple seperation, he would pick you up on this, follow the dti photovoltaics in buildings guide on this, that is what the assesor will have to follow and adhere to. http://www.bre.co.uk/filelibrary/pdf/rpts/Guide_to_the_installation_of_PV_systems_2nd_Edition.pdf

follow the decicion process flowchart is the best way if the scaffold is still up, and you have a tl inverter,bond it, rail to rail to rail to spike