Can`t now my friend - the snake has decreed it worthless :slap
But I will anyway, `cos its aimed me in the right direction
But I will anyway, `cos its aimed me in the right direction
The somewhat complex issues of array frame bonding - thoughts and ideas welcomed
- Thread starter kme
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didn't know the little stars were there...as my son would say,little star, bottom left, :slap
Have read it previously whilst preparing first install, queried it all, asked NICEIC, asked Manufacturer of inverter, caused a small storm, concluded 'nobody had a clue' or didn't want to commit, and applied common sense. Hence my earlier post. The only time I would change my opinion is if the inverter manufacturer specifically stated that for their specific inverter to work in UK it must be bonded, then I would bond it
---------- Post Auto-Merged at 21:33 ---------- Previous post was made at 21:32 ----------
weren't you suppossed to call me this week??
Binky,
This is a BIG issue it seems that there is TOO much that nobody has a clue over!
This is a BIG issue it seems that there is TOO much that nobody has a clue over!
That is my position too - very succinctly put - "scoobed"
Oh, and I was supposed to call Albert, too.......better not do it now :run
Oh, and I was supposed to call Albert, too.......better not do it now :run
Ive gave up trying to remember what about now! :C
OK slightly different view point - if it's so big an issue, how come we don't have PV systems failing all over the place, dead bodies lining the street etc etc
. Of the 40 installs I'm responsible for, they are all working well
Binky,
I mean the issue is the lack of clarity in the requirements, rather than an actual safety issue!
There does seem to be a lot of confusion amongst solar installers due to differing requirements etc.
The systems & standards seem to be lacking in clarity and the manufacturers in the UK don't seem to have a good grasp either.
I personally would not want to bond any exposed metalwork on a roof.
Then comes the dissimilar metals argument with regard to corrosion between the aluminium frames/rails and the copper wire/plated bonding lug.
This would have to be guaranteed for how long? 25 years?
No chance in most places in the UK it would rot away well before that, especially if I understand some of the info in the links above (I only skimmed them briefly).
The capacitive effects in the panels could accelerate any corrosion between dissimilar metals and the point of bonding would be the prime candidate.
I mean the issue is the lack of clarity in the requirements, rather than an actual safety issue!
There does seem to be a lot of confusion amongst solar installers due to differing requirements etc.
The systems & standards seem to be lacking in clarity and the manufacturers in the UK don't seem to have a good grasp either.
I personally would not want to bond any exposed metalwork on a roof.
Then comes the dissimilar metals argument with regard to corrosion between the aluminium frames/rails and the copper wire/plated bonding lug.
This would have to be guaranteed for how long? 25 years?
No chance in most places in the UK it would rot away well before that, especially if I understand some of the info in the links above (I only skimmed them briefly).
The capacitive effects in the panels could accelerate any corrosion between dissimilar metals and the point of bonding would be the prime candidate.
Right with you now sidey. Lack of clarity is always an issue and always will be, but I did a lot of research into this a while ago as previously mentioned, and I just thing bonding framework has greater potential to cause problems then solve them.
As for electrolytic corrosion between disssimlar metals, that has been an issue for years - copper wire into aluminium crimps for one. I have concluded that the stainless bolts are designed to corrode to the aluminum frame componets to prevent them coming undone. I spent 10 years in defence industry working on Aircaft and Naval kit - dissimilar metals were avoided where possible, or threads treated with loctite / anti-seize compounds.
With regards to PV the life span isn't 25 years, it's more like 30-40 years - can't see untinned copper lasting that long for the bonds, but then we often see old earth rods with intact connections. For electrolytic corrosion to occur I would assume a current path is required, earth bonding would certainly help provide that??
See what you mean about the panels, but I got the impression from the SMA link that an earth path is needed (ie steel clad building). The fact that there isn't a major outcry about it would suggest the issue is currently limited to certain installations, and may well take time to develope. I also got the impression the issue was German in origin (makes sense given their engineering). When you see the enthusiastic installation of panels to buildings and factories a few more problems are likely to arise, where as I get the inpression the info wasn't referring to domestic installs, as indicated by the frameless glass panels.
As for electrolytic corrosion between disssimlar metals, that has been an issue for years - copper wire into aluminium crimps for one. I have concluded that the stainless bolts are designed to corrode to the aluminum frame componets to prevent them coming undone. I spent 10 years in defence industry working on Aircaft and Naval kit - dissimilar metals were avoided where possible, or threads treated with loctite / anti-seize compounds.
With regards to PV the life span isn't 25 years, it's more like 30-40 years - can't see untinned copper lasting that long for the bonds, but then we often see old earth rods with intact connections. For electrolytic corrosion to occur I would assume a current path is required, earth bonding would certainly help provide that??
See what you mean about the panels, but I got the impression from the SMA link that an earth path is needed (ie steel clad building). The fact that there isn't a major outcry about it would suggest the issue is currently limited to certain installations, and may well take time to develope. I also got the impression the issue was German in origin (makes sense given their engineering). When you see the enthusiastic installation of panels to buildings and factories a few more problems are likely to arise, where as I get the inpression the info wasn't referring to domestic installs, as indicated by the frameless glass panels.
binky,
Have a look at PD6484 from BSI for corrosion, it may be enlightening!
Have a look at PD6484 from BSI for corrosion, it may be enlightening!
I have a life ...sometimes :slap
will check it out tomorrow.
will check it out tomorrow.
I have had two installs now, both with different inverters sma 3800 and sma 4000 tl where the array produced a ac voltage of 120v.!!!!
This was only discovered ( after all testing was complete and found fault free) when we where cutting down the rails either side of array and my mate claimed he got a shock from the frame( raining heavy at time)
So I went and grabbed my meter set it to dc and checked the frame, nothing??? Changed the meter to ac and was surprised to see 120v ac .
I then switched of system and done all tests again, dc voltage , dc short circuit voltage, and insulation resistance. All test where fine and insulation resistance was clear( tested at 250v result 999 fluke 1654).
After switching system back on I went out and checked the array frame again 120v ac.
Now this was the sma 3800 so according to decision tree I did not need to earth. I may also add this was a completely isolated building erected especially for pv panels completely built from wood.
I then to cut a long story short ,took every panel down, tested individually ( tested ( all ok) and rebuilt array. Switched back on low and behold 120vac..
We then decided to earth the array with earth rod and 10mm crimps, ensuring every rail was earthed use fly leads.
Problem solved no ac on switch on
Now I new this would fix the issue but it still bugs me to this day that I never found any ir issues with any of the panels and why an ac voltage???
So moral of story I now always check the array with meter even if the system does not need to be earthed , depending on topology.
And yes found exact same scenario with tl inverter...
This was only discovered ( after all testing was complete and found fault free) when we where cutting down the rails either side of array and my mate claimed he got a shock from the frame( raining heavy at time)
So I went and grabbed my meter set it to dc and checked the frame, nothing??? Changed the meter to ac and was surprised to see 120v ac .
I then switched of system and done all tests again, dc voltage , dc short circuit voltage, and insulation resistance. All test where fine and insulation resistance was clear( tested at 250v result 999 fluke 1654).
After switching system back on I went out and checked the array frame again 120v ac.
Now this was the sma 3800 so according to decision tree I did not need to earth. I may also add this was a completely isolated building erected especially for pv panels completely built from wood.
I then to cut a long story short ,took every panel down, tested individually ( tested ( all ok) and rebuilt array. Switched back on low and behold 120vac..
We then decided to earth the array with earth rod and 10mm crimps, ensuring every rail was earthed use fly leads.
Problem solved no ac on switch on
Now I new this would fix the issue but it still bugs me to this day that I never found any ir issues with any of the panels and why an ac voltage???
So moral of story I now always check the array with meter even if the system does not need to be earthed , depending on topology.
And yes found exact same scenario with tl inverter...
Hi, no there was no fault on inverter , it was working away fine( only around 120w as I said it was raining) the inverter was connected to sunny webbox so I also checked the resistance readings to earth and the where fine???.
Have had a ground fault recently on an sma 4000tl, turned out to be three nsi panels which where leaking to earth. On testing ir on faulty panels I was getting around 1000 to 2000 ohms....
Have had a ground fault recently on an sma 4000tl, turned out to be three nsi panels which where leaking to earth. On testing ir on faulty panels I was getting around 1000 to 2000 ohms....
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I'll put my suggestion in here.
I believe the inverters switch at quite a high frequency. So could that 120V ac you measured be induced voltage from the switching in the bridge, capacitively coupled to the frame?
If so completely harmless, even if it does give you a tingle in wet conditions. It's this sort of thing you would be bonding to ground stray currents like that.
I believe the inverters switch at quite a high frequency. So could that 120V ac you measured be induced voltage from the switching in the bridge, capacitively coupled to the frame?
If so completely harmless, even if it does give you a tingle in wet conditions. It's this sort of thing you would be bonding to ground stray currents like that.
It would possibly suggest running of cables wasn't billiant ie looped. Other than that i would concurr with pro-Dave
Jono Pashley
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Well today ive been at a Solar PV course and i was told! Copper and Aluminium are similar metals....i beg to differ
Jono Pashley
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banged my head against the desk as the roofers busily wrote that down so they can tell their sparks what to do on jobs......
makes you wonder why the writers of 7671 bother with all those extra tables.......
The course Jono is on is being "taught" (used very loosely) by the QS of the company we`ve been doing sub work for.
He has also told them that using a piece of 4mm FTE from henleys or existing DB main switch, to adjacent "garage board" containing RCD & 16A mcb is not compliant.
I suggested he look at 433.2.2
He did; then said it doesn`t matter, because if there was a "dead short" (his words) in the RCD, the 4mm would be insufficient given the disconnection time of the suppliers fuse.
I`ve asked for a reg. number to back that up, but had no reply yet.
He has also told them that using a piece of 4mm FTE from henleys or existing DB main switch, to adjacent "garage board" containing RCD & 16A mcb is not compliant.
I suggested he look at 433.2.2
He did; then said it doesn`t matter, because if there was a "dead short" (his words) in the RCD, the 4mm would be insufficient given the disconnection time of the suppliers fuse.
I`ve asked for a reg. number to back that up, but had no reply yet.
How dangerous is a little knowledge Wet Fish
