Dti Guide..... When will it be released??

[JulianC]

Is it just me, or does getting a belt from an array frame carrying class 2 modules connected in double insulated cable seem a wee bit worrying? I mean, wtf?

 

[BruceB]

I can safely say it is enough of a poke to make you flinch away from the contact point which could be dangerous if you are at height eg on a ladder,......

Thanks. Interesting. Draft version 3.8 of the Guide would suggest do not bond/earth as I read it. It will be interesting to see where it ends up.

 

[edexlab]

Is it just me, or does getting a belt from an array frame carrying class 2 modules connected in double insulated cable seem a wee bit worrying? I mean, wtf?

The way you have worded this reply seems to imply that there is a short circuit or wiring fault of some kind on the frame, this is definitely not so, all my jobs get tested thoroughly and if there is any doubt I'm not afraid to tell the roofers to take panels off so it can be checked properly,( this happened once when the roofers damaged a cable causing a short and I was not popular but it was justified).
when it first happened I spoke to SMA as I thought it could be caused by some kind of damage while the install was being carried out and they said this was why the TL systems needed grounding, I'm sure you will have read the pdf on this at some point, as I know from your posts that you are knowledgeable , and also the double insulation of the panels and cables does not prevent this potential from transferring to the array frame and is just basic protection
Also as I have posted before its an Ac voltage not Dc .

I would say test one you have done yourself and see what you find seeing is believing


Sma's pdf How does a capacitive discharge occur:

"During operation, the PV module is connected to the alternating current grid via the inverter. Thus, depending on the device type, a portion of the alternating voltage amplitude arrives at the PV module.
At this point, two cases must be distinguished (see illustration):1. Transformerless inverter In almost all transformerless models, half the grid amplitude is operationally passed on to the module.
The set up oscillates with 115 V / 50 Hz. This applies to Sunny Boy / Sunny Mini Central devices with "TL" in the product names.
2. Inverter with transformer In devices with a transformer, the voltage within the PV module fluctuates with a so-called "ripple" of just a few volts.The fluctuating voltage constantly changes the charge state of the parasitic PV capacitor. This is associated witha displacement current, which is proportional to the capacitance and the applied voltage amplitude."

 

[SolarCity]

Thanks for the info from SMA's PDF. With that in mind, I can't see how anyone can really say that bonding the array frame is not desirable. The safety benefits surely outweigh the problems?

 

[JulianC]

The way you have worded this reply seems to imply that there is a short circuit or wiring fault of some kind on the frame,

Not at all. Not doubting your workmanship or observations for a minute. Far from it, I am more amazed that this is considered normal by the likes of SMA etc.

What I cannot get my head around is:
- How an AC voltage of sufficient magnitude to pass on a tingle is present on a frame that is isolated from the modules and cables. It's been a (loooooong) while since I learned about stray capacitances etc. and I will own up to having forgotten pretty much all I learned. However I am amazed that the effect is of such a magnitude.
- How having a transformer in the inverter somehow manages to block this AC transfer, when transformers are generally quite good at transferring AC from one side to the other? I guess it's just a totally different inverter topology....

Me no likee

Do Froniuses (Fronii?)also suffer from this?

 

[edexlab]

Sorry getting a bit tetchy too many long days lately

As for the Fronius I don't know but I have read this is common to TLs , but as I said before, anyone with doubts should test one and see for themselves

 

[Energetic]

Just to stoke this one up again, both myself and another installer i know have been told by our seperate MCS inpectors from NICEIC and NAPIT that not earthing array frames on TL systems or otherwise is fine as long as a risk assesment has been carried out...

What do you make of that then?

 

[SolarCity]

I find it a bit unusual. I will carry on bonding the arrays until a good enough reason can be given for not doing so.

 

[Energetic]

If i had any arrays to bond...

 

[dansk]

If i had any arrays to bond...

Blown off?....

 

[Energetic]

Blown off?....

I wish...

 

[dansk]

Lol......

 

[fiardor]

Blown off?....

Yep, the wife has just finished :82:...........oh i see.......panels......my mistake :lol:

 

[Zach Halley]

does anyone have any updates on this?

 

[TedM]

Last I heard was that it has been delayed following the 12/12 rush. They were still working through draft comments last week.