Help Power One Aurora / Sanyo HDE RCD tripping

[Noddy67]

Odd one. Installed a system last Thursday. all tested. All good.

Went back to adjust panels and as soon as we reconnected the RCD tripped... and continued to (and stand-alone). Seemed to trip as we approached 2kw (of 3.8) but might have been coincidence.

Checked the IR for the cable run. Fine.

(BTW found 12v between the racking and scaffolding (not sure how) but found this in an identical combination around the corner and that's fine).

Any ideas what to look at? I guess even if there was a short on the adjusted panels (ie we damaged a cable or connection) it wouldn't show up on the AC side.

Confused and p*ssed off - it;s the first time with an Aurora inverter and I suspect it...

 

[dansk]

Hi, Can you just give us a little more info - such as how you connected the PV system - was it into the main CU, or did you install a seperate CU? I had it the otherday when connected into main CU the RCD would trip instantly, so i installed a seperate CU and all is fine.

Sometimes you dont need RCD depending on the wiring method, is this something you could do to mitigate the need for the RCD?

 

[Noddy67]

Hi Dansk,

It's a seperate sub RCD/sub now - fitted today after the RCD in the consumer unit was tripping (and hoping that would sort it out).

Good point on ditching the RCD altogether, but it's a TT installation so no choice (I believe).

Have you ever measured a voltate between scaff and racking - both houses back to back have it and I've never checked before on prev. installs.

 

[dansk]

Yeah, if its TL invertor you need to bond to an earth rod if its TT that will cure the touch voltage.

Did the sub unit/RCD cure the problem?

 

[Noddy67]

No joy on the sub-unit.

Bugger - I didn't realise the TL/TT issue. Need to sort that out but it won't sort the tripping will it? how big a cable?

 

[dansk]

10mm, that may cure it. Can anyone else add to this thread?

 

[dansk]

Just add, take a look at dti guide for an array frame earthing tree to help you with future installs.

 

[earwig]

Not sure whether this helps mate but I,ve been reading up on transformerless inverters in an effort to decide whether I should use them. As already stated the array has to be earthed (spiked with tncs). Also, certainly with sma inverters, the minimum rcd size is 100ma presumably to avoid the tripping problem that you have with 30ma. I would say speak to the inverter help line, maybe 100ma rcd will hold. I really don't like the problems these tl inverters throw up for us applying british regs. Can't recall off hand the regs on tt rcd rating.Design software keeps suggesting the tl inverters but I'm suspicious of using them here and try to avoid.

 

[Noddy67]

Hi Earwig,

I think you're right to be cautious. I didn't think this through and took the 'dual' MPPT advantage and didn't read around the downsides.

One thing I have discovered is that there's a Regs requirement, and manufacturers requirement and a best practice requirement and there is clearly no single, absolute answer out there.

Talking to the Power One people today (very helpful but...) they say there's a new paper out there that hopes to settle this but I think that should have been worked out before TL's Inverters were given MCS accreditation.


Live and learn (and cringe).

 

[dansk]

Noddy, did you cure it?

 

[Deleted member 38070]

Earth rod for rails (MET/rod on tt - MET TNS (rod for tncs/out of equipotential zone) 10mm (as mentioned above), tl inverters are put on a b type rcd 100mA when rcd is required (ie TT etc), put on seperate sub/rail, TL earth leakage is quite high and will trip 30mA rcd intermittantly..(peak in generation). hope this is helpful ;-)

 

[earwig]

Thanks for that Sniffy, my thoughts exactly. One scenario I thought of and am interested in your opinion. What about tncs with rail
in equipotential zone, say dormer window. I was thinking bond to met and a rod as main bonding is required but there's also the
issue of voltage from the ground ladder scenario.

 

[dansk]

Grey area that one, to follow the book, bond to MET.

 

[daytona600]

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[Deleted member 38070]

View attachment 6894i am led to believe that any metalwork on the roof is out of the e/zone, its a bit of a grey area, and has had much debate.. if i was doing a job with the scenario, it'd be an earth rod as i treat anything on the roof as outside the zone. (there are always exceptions! if it is close to metalwork/can be touched etc etc then e/zone can be extended and bond to met) other opinions may differ, i follow the earth decision tree in the dti guide. about time they updated it really.... i have attached the page (pdf) of the decision tree, not very familiar with this forum yet, im a newbie ;-) so hope ive uploaded it correctly. hope this helps

i've been doing pv electrical work for about 18 months, so im not an expert, there is a lot of mis information about, i've talked to fronius and sma about the rail earthing scenario... transformer inverters are easier, just leave frame floating, i am intrigued at what everyone elses opinions on the subject are?? though it is varying from the rcd issue!

not understanding your earth ladder quote, can you explain it a bit?? ive had a long day!!! ;-)

 

[Deleted member 38070]

id be interested in sourcing this ""paper"" do you know where i can get it? link? many thanks ;-)

 

[Deleted member 38070]

View attachment 6899View attachment 6899 i know this is not aurora, this is an interesting document by sma on the use of rcd's with their inverters (page 8)

 

[Noddy67]

just an aside to wrap this up... the array worked fine for four days, dripped like mad on day 5 (when we fiddled with it) but has gone back to being trip free with no further work.

all I can imagine is that we unplugged the panels under load (it was early on an overcast day) and maybe that p*ssed it off.

finally thanks to all who contributed and helpled (particulary Dansk). Very much appreciated... Richard

 

[dansk]

Your welcome