2 Phase PV Problem with RCDs

[fitzsparks]

I have just installed a 2 phase system with 2 Solar Edge inverters (3.7kW per phase) Each pv system is fed through a shared Elster A1100 3 phase meter and each one runs fine on its own. When connected at the same time the RCDs on both system trip. The only way I can make it work is to bypass the generation meter, so the problem appears to be at the meter. We have done many single phase installations, and could use 2 single phase meters, but that requires two FIT applications, which seems mad!! Anyone got any ideas?

 

[Gavin A]

firstly, do you actually need RCD protection on the circuit under BS7671 17th?

if not, the solution to your problem is at hand.

 

[BruceB]

And secondly, x2 single phase meters does not require x 2 applications. Although the computer might say no for the simplistic suppliers.

Have you got a diagram of how the rcds are connected? Perhaps a 3 phase rcd would do it.

 

[SolarCity]

Presumably the meter is sharing the two neutrals also? This will be what is causing it to trip out. Go for two meters if you need an RCD.

 

[fitzsparks]

Thanks for the replies.

It seems that it is an issue that the phases are being joined in the meter, which is enough to trip all the RCDs on both phases. The only way we seem to be able to get both PV systems working is by by-passing the generation meter (which somewhat defeats the object of having a Generation Meter!!).
Is there a multi-phase meter available that is electrically seperate inside, so it acts like two single phase meters but with a common display? Your thoughts are eagerly anticipated!

 

[Earthstore]

Not an expert here, but it sounds like you have joined 2 phases together, in the generation meter, so with one neutral you will be causing a huge imbalance, hence RCD problem.
Not too sure but could you use a 3 phase generation meter, but only use two of the phases? or just use 2 single phase generation meters.

One small point though, you have not balanced the phases by only have pV on two out of three.

Just some thoughts.

 

[BruceB]

Sounds like the rcds might be on the grid side of the meter. Put them on the inverter side and it should be ok.

 

[Earthstore]

From my understanding of this, that could work, but two phases would still be connected at the generation meter.
Maybe it would be best is if the OP posted a sketch, or some pics, then we all would have a better idea.

 

[SolarCity]

+1 to Bruce's idea.

 

[Earthstore]

Sorry, must learn to read..
Just reread the Op's post and Bruce is correct.

 

[Worcester]

+2 to Bruce's it's the obviuos solution

 

[SibertSolar]

Agreed

 

[fitzsparks]

We've sorted it!! Thanks for the suggestions. We wired it up : inverter to RCD, then the 3 phase meter, then split out to AC Isolators on respective phases, then the seperate small Fuse Boards and on to the respective main fuse boards. Seems very obvious now, but just been used to putting isolators and meters in any order after inverter. Will know for next time!!

 

[SibertSolar]

Glad you got it sorted, common enough mistake to make ;-)