PV causing RCCB to trip

[down2earth]

Hi all,

To keep it short and to the point, my neighbour has a PV array on a shed which goes to an inverter, then to a 20A RCBO (I think) in a small CU and then back to the main CU in the house where it goes to a Hager 40A RCCB (30mA). The 40A Hager in the house trips periodically for no reason, I have been advised that this needs to be changed to a Type A RCD as PV arrays cause fluctuations that can trip the existing RCCB. Is this in line with other peoples understanding?

Thanks for any help.

Down2earth.

 

[sedgy34]

tricky one!! try putting first a 20a mcb next to the 40a rccb and a 20a mcb in the shed

 

[yellowvanman]

Your bog standard RCD is a Type A, potentially you may need a Type B RCD if dc is 'leaked' onto the ac.

There could a couple problems with the install if I understand it correctly. Couple questions to ask.

In the house CU the circuit supplying the shed is protected by an RCD that protects other circuits? If this is the case then an inverter shouldn't be on a circuit that shares an RCD with other circuits. Reason why is that if a person get a shock and trips the RCD (within 40ms) the inverter is still kicking out 230V for up to 5 seconds, even though the RCD has tripped.

Potentionally the PV circuit shouldn't need RCD protection unless cables are buried in walls etc.

Some inverter manufacturers recommend only 100mA RCDs on their equipment. Need to know what inverter is fitted.

 

[Earthstore]

A common problem here is the AC cable from the house to the garage is too small, it should have less than a 1% volt drop, if the incoming voltage is on the high side when the PV system is producing well it will go over voltage because it has to match the mains supply.
I hope this helps.

 

[yellowvanman]

A common problem here is the AC cable from the house to the garage is too small, it should have less than a 1% volt drop, if the incoming voltage is on the high side when the PV system is producing well it will go over voltage because it has to match the mains supply.
I hope this helps.

I know you're trying to help but this problem wouldn't cause the RCD to trip.

 

[BruceB]

D2E, You do not say what type of inverter it is, but many are not suitable for 30mA rcds. The Hager 40A(30mA) is tripping because of too much residual current. Changing it to a type A is not likely to make any difference if it is still a 30mA one, because the residual current will still be present. All the type A bit does is mean the rcd can operate in the presence of pulsating direct currents (there is a wiki entry). Why is it going through the hager rcd? Is it because it is TT? If so then increase the value to 100mA or 300mA and add additional protection to those circuits that require it separately. Often it is best not to have the pv on a rcd if possible. Can it bypass the rcd? It is a bit difficult to give authoritative advice without knowing all the details so I would suggest your neighbour gets the installer back to sort it out.

Regards
Bruce

Edited to add: I see lots of people got in whilst I was typing! YVM, standard rcds are type AC in UK rather than type A I believe.

 

[Earthstore]

I know you're trying to help but this problem wouldn't cause the RCD to trip.

Sorry, you are right.
I really must learn to read...

 

[yellowvanman]

Edited to add: I see lots of people got in whilst I was typing! YVM, standard rcds are type AC in UK rather than type A I believe.

You are correct , of course. :shame:

 

[cbw]

Sounds to me like John Wayne did the AC side???

 

[down2earth]

Thanks for all the replies, I am out of my comfort zone on this one so I think I will get the neighbour to get the installer (his son!) back to sort this one out, it sounds like there are a lot of variables that could be an issue.

Thanks again

D2E