RCD Tripping

[chrismacis]

hi

i have an old customer who's pv installation is tripping out when raining/wet. 16 x 245w Sharp panels with a Power-One PVI-3.6 TL inverter. The inverter is showing a current leakage from the panels which obviously increases when soaking. All mounting structure is bonded

There is a 30mA RCD installed and ideally i would like to swap this out for a 100mA RCD however i am unsure if it would be compliant under 17th ed regs.

DC cable is coming through the roof tiles and cables are clipped to rafters next to the inverter. For the ac cable we have drilled through the loft floor and fed direct into consumer unit.

Could anyone advise if this would be compliant if I install the 100mA RCD or would I need to swap inverter out for one with a transformer?

Thanks

 

[SolarCity]

For what reason is it protected by an RCD now?

 

[chrismacis]

It is a transformer-less inverter

 

[Earthstore]

It sounds like you have water getting in somewhere, probably a joint or maybe a chaffed cable, good luck trying to find that one.

In my opinion you need to find the fault.

 

[Gavin A]

Is this a shared RCD, or an RCD that is dedicated to the solar circuit only?

The answer to your 100mA RCD question lies in the answer to this question.

 

[chrismacis]

Is this a shared RCD, or an RCD that is dedicated to the solar circuit only?

The answer to your 100mA RCD question lies in the answer to this question.

The RCD is dedicated to the solar only in its own mini board.

 

[chrismacis]

It sounds like you have water getting in somewhere, probably a joint or maybe a chaffed cable, good luck trying to find that one.

In my opinion you need to find the fault.

All panels cables etc have been check by myself and an independent electrician and we can find no loose connections or damage....

We both feel the 30mA RCD is too sensitive

 

[Gavin A]

The RCD is dedicated to the solar only in its own mini board.

switch it for a 100mA then, unless there's any unusual reason why this wouldn't be compliant with 17th edition regs, but assuming you've not installed a socket, not installed in a special location, and used safe zones etc then it shouldn't be an issue... or you could just not use an RCD at all as there's no requirement for it.

 

[SolarCity]

I'd go for not using one at all. Most TL inverters don't require RCD protection.

 

[Worcester]

Go through the proper isolation procedures and also check the voltages from the DC+ve to earth and the DC-ve to earth on each of the strings, that will give you an idea as to where the fault lies.

It appears that some MC4 connevtors are not as watertight as they could be and assuming that they've earthed the array (Guide V2) there could be a leak to earth, the above will identify if there is and a guide as to where it is.

 

[yellowvanman]

and used safe zones etc then it shouldn't be an issue...

If cables are concealed in safe zones they still need a 30mA RCD, I think you mean exposed cables (or surface run).

 

[Earthstore]

All panels cables etc have been check by myself and an independent electrician and we can find no loose connections or damage....


We both feel the 30mA RCD is too sensitive

But if the fault/tripping only happens when it is wet and the system has been fine for some time, does that not suggest that you have water ingres somewhere?

 

[Gavin A]

If cables are concealed in safe zones they still need a 30mA RCD, I think you mean exposed cables (or surface run).

yep you're right, sorry my brain's still a bit fried from the flu... tbh we do 95% of our AC runs either in SWA externally, or surface mounted if it's right next to the inverter that I had to look that up in the regs just to double check exactly what it said again. Last time I can remember channeling a run was about 6 months ago, and we pretty much use RCD's on all our circuits anyway as they come with the garage units we get.

 

[Gavin A]

But if the fault/tripping only happens when it is wet and the system has been fine for some time, does that not suggest that you have water ingres somewhere?

not necessarily as the capacitance issue with the panels that causes the minor earth leakage is worse in damp weather, so it could just be that, or it could be rain getting in to the connectors... testing should let you know which, though it might still not show up if it's dried out enough before you test the circuit.