DC Cable buried <50mm in wall

[Gavin A]

I'm assuming here that the 3600TL isn't listed because SMA just haven't got round to updating the document since it's release.

 

[moggy1968]

I will be honest and at this point and time have no evidence to prove it, my suggestion is just that, a suggestion. I have never come up with the instance where we have had to bury a cable in a wall so was not really offering expert advice, however if you formulate an "A" type RCD is better and will do the job then the goal is achieved.

If you feel RCD protection of any kind is not suitable then more fool me for suggesting it.

However between us I would say a lot are not aware they are meant to use a type "B" RCD and on the quiet pooing their pants, even though (i not looked) there are probably many threads on this.

I think this is unfamilliar territory for all of us!
best option in my mind is just not to bury the cable!

 

[Glen Powell]

Totally understand and if that technology is in that inverter so be it, I look at it from two different points of view, if in court and you say you followed the manufactuer instruction then it is the manufacturer at fault. If you follow the regs and something happens the manufacturer could place you at fault. catch 22. however if one does not degregate the other then what is the harm.

You imagine trying to get a Chinese Inverter Manufacturer over here to plead their case, SMA is different, but belt and braces.

 

[Gavin A]

Totally understand and if that technology is in that inverter so be it, I look at it from two different points of view, if in court and you say you followed the manufactuer instruction then it is the manufacturer at fault. If you follow the regs and something happens the manufacturer could place you at fault. catch 22. however if one does not degregate the other then what is the harm.

You imagine trying to get a Chinese Inverter Manufacturer over here to plead their case, SMA is different, but belt and braces.

one of the reasons we've never used anything other than SMA, Power-One or Dhiel.

If what you're saying is anyone installing dodgy chinese TL inverters who's provenance they're so uncertain of that you think it best to install a type B RCD just in case, then I'd agree, but with the caveat that I also think it unwise to be installing something you're not 100% certain about in the first place.

bottom line, I'm installing a grands worth of kit from the worlds biggest manufacturer, and the manufacturer is telling me specifically that the kit not only doesn't need a type B RCD, but to be on the safe side they've already installed their own secondary protection RCMU device that basically does the same job as a type B RCD anyway, but set at a specific level to avoid nuisance tripping......... I think I'll take SMA's advice on that one, given that they're the experts on their own equipment.

 

[SolarCity]

I agree with Gavin on this one.

As for burying the DC side, surely a B type RCD at the array end of the DC run would solve this problem, albeit expensively?

 

[SibertSolar]

*sigh*........

 

[Gavin A]

FWIW, I'm coming round to Bruce's idea, but only for transformerless inverters where the DC side may well not be fully isolated from earth while the inverter is engaged, so tripping the RCMU side of the inverter would effectively cause the DC side to become isolated / separated from earth again other than via the existing fault path, so there is no potential return path, thereby making the fault safe until an engineer arrives to sort it out.

Only problem is that the engineer needs to be trained to be very aware that all extraneous conductive parts in the house could be carrying DC fault current and potential to the other side of the DC circuit when attempting to resolve such faults, but I suppose this should come under the trained / skilled persons category (or whatever the term is). I'm not convinced many PV technicians / sparks are currently trained to be aware of this issue though.

For galvanically isolated inverters my original opinion still stands, and earthing the armor removes the protection afforded to the DC circuits from it being a separated circuit, and I don't see any benefit to this.

Must admit though that I agree with Moggy, and think avoiding burying the DC cable is by far the best option if at all possible.

 

[BruceB]

FWIW, I'm coming round to Bruce's idea...................

............... rushes to check PI insurance in place!

 

[Echolite]

Anyone tried the new Cable Capping product Called Rapid Cap, I heard its Quick to use and less hassle unlike the traditional cable capping.​

 

[moggy1968]

still doesn't provide adequate mechanical protection though