PV on shared RCD

[yellowvanman]

Just quoting for an Immersun and customer has sent me photos of the install (so I don't need to make a site visit). I notice that the PV is on a shared RCD, do I mention it and recommend they get the installer back?

 

[jason121]

When was the system installed ?

 

[yellowvanman]

18 months ago (ish)

 

[Gavin A]

mention it and suggest you can sort it out for £x or they could attempt to get the installer back, but as it's a bit of a moot point about whether it's allowed or not they probably wouldn't feel under any obligation to sort it out.

WHat inverter is it? If it's an isolating transformer inverter it's unlikely to be an issue, and let's face it if they've had it in for 18 months and not had a nuisance tripping issue then it's probably not a problem - if they have had this issue, then I'd just offer to sort it out for them for a reasonable fee.

 

[yellowvanman]

Inverter is Fronius IG TL.

So the fact that the inverter can still output for 5 seconds is not a problem?

 

[Gavin A]

there are other threads explaining this more fully, but that side of things shouldn't be a problem as once the RCD trips all the circuits then lose their return earth fault path to the inverter, so those circuits effectively become protected via the separated circuit method for those 5 seconds... or there's no circuit back to the inverter from an earth fault, so any problems caused by the earth fault will automatically cease to be a problem.

There are apparently some issues with certain TL inverters causing the RCD units to stick, presumably due to too much DC leakage current. I think someone posted up about the Samil inverters likely causing issues as they allow for much higher DC injection than the SMA, or Aurora - not sure on the Fronius.

It's certainly not best practice, and we don't do it, or recommend it, but it's not necessarily actually dangerous as long as it's not interfering with the RCD function itself.

 

[jason121]

Wasn’t this allowed 18months ago on the DTI 2[SUP]nd[/SUP]edition

 

[yellowvanman]

Just re-read the DTI guide (not the one thats not been issued yet!) and it says:

Where an electrical installation includes a PV power supply system
without at least simple separation between the a.c. side and the d.c.
side, an RCD installed to provide fault protection by automatic
disconnection of supply must be type B RCD according to BS EN 60898
(IEC 60755, amendment 2).

The RCD installed is not a Type B

 

[jason121]

Fronius TL does not a type B RCD

 

[Earthstore]

So, it may not need to be on an RCD at all.
If there are no buried cables, and the Inverter that is used does not specify RCD protection.
So many if's and but's, this has been covered many times, but there is still confusion.

 

[yellowvanman]

Fronius TL does not a type B RCD

Sorry, don't quite understand that!

 

[jason121]

Sorry fat fingers Fronius TL do not have to be connected to a Type B RCD
They need to be connected to a type A if buried in wall or you work to the 3rd edition guide, but you did say that the install was 18months ago

 

[sedgy34]

its in the regs type B rcd for pv if its got to go on a rcd

 

[jason121]

nooo had discussion with Fronius while back.
There was a thread on here not so long ago

 

[jason121]

Watch out Worcester about