Hi all, the PV guys installed their stuff today but as soon as the Inverter is switched on it trips the 100ma S RCD at the origin of the submain feeding the CU. However, it's not tripping the 30ma RCBO which it's connected to in the CU. Any ideas anyone please?
Sounds like a wrong connection on the sub main circuit somewhere, N- E maybe? Is the sub main serving other stuff ok?
Yeah, the submain is supplying the CU which is supplying the whole house. All circuits off seperate RCBO's. The 100ma S is at the origin of the submain as it's a TT. Not had any issues with it until the PV connection today....
Ok Sparks, that rules out my wrong connection theory then! Only other possibility I can think of is a faulty inverter?
Apparently, they suspected this and tried another inverter but to no avail. Still trips as soon as connected. Maybe for some reason the inverter doesn't like the ControlGear RCD? However, the RCBO is ControlGear also so would've thought it would trip this too. Maybe should try a different brand 100ma RCD do you think?
Has to be worth a try I suppose, might also be worth temporarily fitting one of the 30m/a ones from the c/unit in place of the 100m/a one just as a test.
Tested both the RCBO and RCD today and both tested fine. Took out the Control Gear 100ma S RCD and replaced with Hagar... PV inverter fired up and all is well. So it's official, Fronius inverters don't like CG 100ma RCD's!
Glad you've sorted it mate, bit of an odd one though isn't it. I've fitted lots of CG c/units and never had any rcd problems with them but of course never used the same combination as you have so maybe it is just a compatibility issue!
Just out of curiosity, I'm going to try an MK RCD in there at some point to see if that works ok too. You're right Seneca, just a compatibility issue, that Fronius inverter must leak out something strange which is well beyond my ability to understand! That said, it works fine with the Control Gear 30ma RCBO.
PV Inverters are notorious for this caper. If initial tests prove the RCD/RCBO OK just swap out for a diff manuf' U shouldn't have to but this is just the way it is!
A very good point. The ramp test I did on the original RCD showed it tripping at 70ma. I then did the same test on the replacement and it tripped at 80ma. Only 10ma between them. What I didn't try at the time was disconnecting all other circuits leaving only the inverter on. Maybe that's what I should try, to test your theory
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