Array frame earthing

[paulsamuel1984]

Having read the draft PV guide edtion 3 out for review, I see very little instances where you would earth or bond an array frame.

I appreciate there are instances where you should but these seem quite rare reading the new guidline, even with transformerless inverters.

is anyone still earthing their array frames when using transformerless inverters or already starting to move over to the new guidelines and keeping the majority of their frames floating??

 

[JulianC]

The new guidelines are still in draft form and subject to change. You shouldn't be working to it, no matter how convenient it might be. If you are fitting a transformerless inverter, bond the array frame every time.

 

[paulsamuel1984]

Thanks Julian,

Thats still my thought process at the moment. I am still earthing / bonding my array frame as per the original guidlelines. Thanks for the response.

 

[Coleman]

Thanks Julian,

Thats still my thought process at the moment. I am still earthing / bonding my array frame as per the original guidlelines. Thanks for the response.

I would'nt bond the array unless you can touch the panels from a velux window etc. because your potentially introducing a fault path this was confirmed by ECA

 

[powervan]

last week nic part p inspector said NO NEVER EARTH ARRAY!! i just dont use TL invertas now!!!!!!!!!!!!!

 

[moggy1968]

my concern with this has always been if there is a fault on the DC cabling causing the array frame to become live without bonding the first you'll know about it is when you fry yourself going up there to investigate. It does concern me having a large metal structure, potentially having potential, so to speak, and no earthing, even with a transformerless inverter. It's a concept I'm having trouble getting my head round.
Without bonding what would stop you getting fried?
Any explanations at a suitably simpleton level gratefully received, I am after all a bear of very little brain!!!

 

[edexlab]

My last Niceic inspection and Mcs inspection the assessors knew very little about Pv and most of the assessment seemed to be talking about the pv side of the install i was using.
I know that in Germany its common practice to earth all arrays TL or not and if you read the inverter manuals the manufacturer usually reccommends you do so ,even though the Regs/DTI guidelines etc say otherwise

 

[powervan]

bear of very iccle brain!! u be a senior member in no time

 

[powervan]

ooops u r ))))))))))))))))))))))))))))))))

 

[SolarCity]

We're still bonding frames.

In general, a fault from the panels to the frame shouldn't be that dangerous in itself as there shouldn't be any potential to earth anyway. That is unless I'm missing something.

 

[powervan]

i spoke to window cleaner yesterday who cleans them for 3 of his clients! i said did he shut it down first? no? i did point out if he had ladder on wet grass(silly but true) then he holds on at top to ladder! other hand sponge!!(yes i no they dont use sponges) but u get the idea!!! if fault (voltage) on array he will be a FLYING oops FRYING window cleaner!! but what do i no? nothing thats y i steeeeeer clear of TL invertas unless totaly stuffed!!

 

[moggy1968]

Big solar
as I understand it, and as I say I do have a conceptual problem with this, if there is a short between the DC and the frame, that frame will hold a potential. it will continue to hold that potential until it is given a path to earth, through a bonding cable if present, or the window cleaner if it isn't!!

 

[powervan]

by jove i think he got it!! perhaps we need someone to demostrate it? any takers!!!!!

 

[bumcrack]

All elasatictrickery wants to do is get back to it's point of origin.

If a DC pos is touching the array frame, it will do nothing untill it finds the DC neg of the source. It can't flow until that path is made.

This is why bonding DC down to ground is frowned upon, in doing that, you are creating a path.

 

[GreggElectrical]

All elasatictrickery wants to do is get back to it's point of origin.

If a DC pos is touching the array frame, it will do nothing untill it finds the DC neg of the source. It can't flow until that path is made.

This is why bonding DC down to ground is frowned upon, in doing that, you are creating a path.

That is my understanding too. The DC +ve is only interested in getting to DC-ve. This means even if the +ve is shorting to the frame, you shouldn't (in theory) get a shock as there is no potential to earth. Kinda like if you were to wire up 10 12V batteries (120v) in series an touch the live terminal. Am I on the right track?