main connection to consumer unit or meter tails

[marc8]

hi all
been fitting immersuns for a while now & whilst installing one the other day found that 2.5T/E

been placed inside main consumer unit with tails at point of entry to main switch, seen this twice now in last
couple of months. have the regs changed that you can feed another isolator from mains with 2.5T/E without
going through a Fuse/Cb first or is this just acceptable for solar pv as fairly new to solar myself just thought
i would ask, if i installed this during my normal day at end of year i would get pulled for it?

 

[SPARTYKUS]

No its not okay because the 2.5mm2 twin and earth will melt / catch fire a long time before the main fuse goes. So the circuit is a fuse (or bomb, depends how you look at it)

 

[marc8]

hi spartykus
customer was well proud of their install i did not mention, not my place really.
but if you have to belong to MCS & alike i thought they would be hot on this sort of thing

 

[SPARTYKUS]

You'd think so!

 

[Gavin A]

The argument for being allowed to do this goes that it's a current limiited device, and according to BGB it's allowed to run a circuit for a current limited device without overload protection, and the suppliers fuse would supply fault protection.

So by that reading of the regs, it would seem to be allowed, however G83 specifies seperate overload protection for the circuit, so it's actually not allowed for solar PV installed under G83 or G59.... so basically all grid connect solar PV, as the DNO don't want anyone to be using their fuse as the only fault protection on the circuit whether it's current limited or not.

so no it's not allowed, the installers doing it are breaking G83 regulations and therefore the system doesn't have permission to connect to the grid

 

[telectrix]

every day i learn more about solar. by time i'm 70, think i might just know enough. ( shut up , geordie!. :rofl: ). :tounge_smile:

 

[marc8]

hi Gavin
i have seen it a couple of times mainly when fuse box is old & no spare ways as reading all through your notes would have been easy solution if it was allowed but thought i would ask first cheers

 

[BruceB]

So by that reading of the regs, it would seem to be allowed, however G83 specifies seperate overload protection for the circuit, so it's actually not allowed for solar PV installed under G83 or G59.... so basically all grid connect solar PV, as the DNO don't want anyone to be using their fuse as the only fault protection on the circuit whether it's current limited or not.

so no it's not allowed, the installers doing it are breaking G83 regulations and therefore the system doesn't have permission to connect to the grid

Have you got the reference for that, so I can read it? The downstream PV mcb will be providing overload protection separate from the DNO fuse.

 

[puddy]

Can you condemn the fuse box? The same way an unsafe gas appliance would be condemned or do uninstall the circuit to make it safe or walk after telling the client?

I am not an electrician just a homeowner with solar

 

[AndyL]

The argument for being allowed to do this goes that it's a current limiited device, and according to BGB it's allowed to run a circuit for a current limited device without overload protection, and the suppliers fuse would supply fault protection.

So by that reading of the regs, it would seem to be allowed, however G83 specifies seperate overload protection for the circuit, so it's actually not allowed for solar PV installed under G83 or G59.... so basically all grid connect solar PV, as the DNO don't want anyone to be using their fuse as the only fault protection on the circuit whether it's current limited or not.

so no it's not allowed, the installers doing it are breaking G83 regulations and therefore the system doesn't have permission to connect to the grid

The 100A fuse may not give fault protection either to a 2.5mm cable

 

[JulianC]

Does the 2.5mm out of the main switch feed in to an MCB in a dedicated consumer unit for the PV circuit? If it does then overload and fault protection might be OK, despite the out-and-out shoddiness of the execution. If no MCB then there's a problem. As AndyL says, 100A fuse won't provide fault protection.

 

[marc8]

hi
the 2.5mm does go to a consumer up the wall so there is a 16cb at that point, which provides 16amps for the cable
to the inverter / ac isolator.
but am sure that should only change size of cable after going through overcurrent protective device otherwise
cable is not rated for fusing.

 

[Gavin A]

Have you got the reference for that, so I can read it? The downstream PV mcb will be providing overload protection separate from the DNO fuse.

I was working on the basis that there wasn't an MCB at all, but might have misunderstood.

the reference is the G83/2 engineering document, not sure which page as I'm working from memory.

 

[Gavin A]

The 100A fuse may not give fault protection either to a 2.5mm cable

probably right, I considered it as an option for 6mm2 on a job a while back before ruling it out after checking the G83 regs. I stopped at that point so didn't do those calcs to check that side of things.

Twas a thread elsewhere on here that prompted me to investigate it

 

[Gavin A]

hi Gavin
i have seen it a couple of times mainly when fuse box is old & no spare ways as reading all through your notes would have been easy solution if it was allowed but thought i would ask first cheers

henley block on the tails, though you're then into the issue of safe isolation.