Pv on rcd

[gnselectricals]

Hi guys doing a solar iboost as a subby the other day and noticed that the Pv supply had been connected to a shared RCD, situation was TT supply feeding 2 dbs at the origin each with a 30mA main switch RCD.
I was always under the impression that this was incorrect but read through the Dti guide briefly and couldn't find a mention but did find a NIC ? best practise guide saying that a shared double rcd is ok as it will disconnect line and neutral in a fault, but a single pole RCBO won't so can't be used ?

Just before I go back to my client looking like a cock [emoji23]
Cheers

 

[gnselectricals]

Anybody out there [emoji23]

 

[Deleted member 26818]

One of the problems with the majority of RCDs (types A & AC), is that they are no good for d.c. current.
Have to be type B.
Not sure that there would be a problem using a single pole device with d.c. as long as it's the positive being switched?

 

[Worcester]

What make model of inverter? It makes a difference to the answer.

 

[gnselectricals]

What make model of inverter? It makes a difference to the answer.

A solar edge not sure of model single phase 4wk domestic job

 

[sam400]

I know nothing about PV but have just been reading about this in PE.
It's because in the event of an earth fault on a final circuit THE RCD will remove the mains supply but the Invertor will continue to supply voltage to the shared bus bar until it is shut down this could take a few seconds - well over the disconnection time of the RCD.

 

[uksparks]

Hi,

i put my PV on an RCBO! Works fine.

i couldn't not due to the routing of the cable.

 

[davesparks]

Hi,

i put my PV on an RCBO! Works fine.

i couldn't not due to the routing of the cable.

Which end of the cable did you put the rcd?
Bearing in mind that there is a source of supply at both ends of the cable.
Or does a PV system disconnect within milliseconds of the supply going off?

This is a genuine question I have never yet got an answer to

 

[uksparks]

Well I have no idea, I connected it on an rcbo's in the main board, not the PV end.

i don't see what else I can do, it's a grey area I think, I don't know what the answer is either.

i would imagine that the inverter disconnects under a certain time to comply would it not?

 

[Leesparkykent]

Reg 712.411.3.2.1.1 page 251 byb

Edit: Should of quoted the OP.

 

[Leesparkykent]

Which end of the cable did you put the rcd?
Bearing in mind that there is a source of supply at both ends of the cable.
Or does a PV system disconnect within milliseconds of the supply going off?

This is a genuine question I have never yet got an answer to

The pv can take up to 5 seconds to disconnect under G83.

 

[uksparks]

Reg 712.411.3.2.1.1 page 251 byb

Edit: Should of quoted the OP.

Im in bed now, what's the gist of it?

 

[uksparks]

The pv can take up to 5 seconds to disconnect under G83.

Hmmm I see.

what would you do? I can't say as I know really.

 

[Leesparkykent]

Im in bed now, what's the gist of it?

On the a.c side, the PV supply cable shall be connected to the supply side of the OCPD for automatic disconnection of the circuits supplying current using equipment.

 

[davesparks]

The pv can take up to 5 seconds to disconnect under G83.

So I would be right in thinking that an RCD won't provide protection to the typical PV circuit you see in domestic installs.

 

[davesparks]

Hmmm I see.

what would you do? I can't say as I know really.

Install the PV circuit in such a way that it does not require RCD protection as an RCD will not provide protection to the circuit.

 

[uksparks]

Are you saying just put it on an MCB?

 

[uksparks]

Surely having an RCBO on it is going to be better than just having an MCB?

 

[davesparks]

Surely having an RCBO on it is going to be better than just having an MCB?

Not if the rcbo doesn't provide any protection. I would say that fitting rcbo protection would be worse than an MCB as it would make it appear to have RCD protection when in fact it won't work, plus of course it makes the person who installed it look like they don't know what they are doing and don't understand what they are doing.

The rcbo will detect a 30mA electric shock and disconnect within 300mS which could save someone's life, except the inverter will continue to supply power into that person for up to 5 seconds, ensuring that they are well and truly dead.

 

[Leesparkykent]

So I would be right in thinking that an RCD won't provide protection to the typical PV circuit you see in domestic installs.

Hmm its food for thought...i think you are right. Do you think (iv) of 551.7.2 should apply?