PV tripping another RCD on seperate circuit?

[Morgan keith]

We have installed a PV system which has 3 inverters and is protected by a 300mA RCCB. It runs directly back to the main incomer. However there's another circuit which runs from the same point which is protected by a 100mA rcd which is tripping. The 100mA RCD feeds a distribution board which supplies a calf feeder and a couple of sockets etc. Firstly I can't get my head around why a sub-circuit is tripping? Secondly, is there anything stopping us from upgrading it from a 100mA rcd to 300mA to stop the tripping? I've looked at the regs numerous times but nothing's too clear!

Many thanks

 

[LightGEN]

At the risk of stating the obvious.....are you absolutely sure there isn't a fault with the circuit which is tripping out or the equipment connected to it?

 

[Morgan keith]

Yes. It has been 100% fine for years and the day the PV got installed, it started tripping. The 300mA PV RCD doesn't trip but the other sub-circuit does as it's it's only rated at 100mA. I know it's common for RCD's to trip because of a PV install (hence the 300mA RCD) but am struggling as to why it's tripping if it's on a seperate circuit

 

[LightGEN]

I can't say that I've ever experienced any problems with RCD tripping being caused by a PV installation - others may have of course. Where a transformerless inverter is used there is, at least in the case of SMA TL inverters, a manufacturer specification that additional RCDs feeding the PV circuit be of 100mA trip rating. Non TL inverters work quite happily with 30mA tripping RCDs.
What make/model are the inverters?
I think I'd still test the 'farm' circuit - that 'it's been working for years' argument doesn't figure 'coincidence' into the equation! :blush5:

 

[fiardor]

We have installed a PV system which has 3 inverters and is protected by a 300mA RCCB. It runs directly back to the main incomer. However there's another circuit which runs from the same point which is protected by a 100mA rcd which is tripping.
Many thanks

When you say same point i assume you mean a henley block?

 

[Gavin A]

have you checked the connections, make sure you've not wiggled something loose a bit on the other circuit during the work?

 

[Morgan keith]

The inverters are Solarmax 15MT. Tested the other circuit and it was fine. Yes runs off a henley block. Turned out to be an issue with one of the inverters so swapped it to a new one and it's good now. Still beyond me as to how it was tripping the other RCD!! But anyways.
Many thanks guys!

 

[SibertSolar]

Just out of curiosity, what was the make/model of the other RCD that was tripping?

 

[Morgan keith]

Protek 100A 100mA. But was a completely seperate circuit from the PV

 

[SibertSolar]

ok, thanks Morgan. Does seem a bit odd that it was tripping.