replacing old consumer unit in garage with new

[trev]

"the consumer unit is fairly new and seems up to the 17th edition regs"
I'd expect a trainee to be able to tell the difference between a 17th compliant CU and a one that wasn't compliant unless of course that trainee had only got a few weeks under his belt, in which case the trainee should be nowhere near a CU.

The 4 lives going into one MCB could simply mean that this garage was originally wired by an idiot! How big is this place? Surely the most it would need is two flourescents and there's absolutely no reason why you couldn't put them on one circuit.

I note you say it's fairly big and that they want to convert it at some point in the future but convert it into what exactly? My guess is that it's being converted right now into some sort of accommodation. As a trainee I think you should steer clear of this because it could and probably will come back to bite you on the arse.

I agree that we all have to start somewhere but it comes across that you're very unsure about what is happening here, as most trainees would be.

 

[Octopus]

thanks for the reply, the swa is buried in the wall, and also when that recent fault happened in the garage, only the 45a mcb was tripped in the house and not the rcd

So what does that tell you then??

 

[ratkins]

What about equipotenal zone?

 

[Engineer54]

so if i install a new consumer unit, should i just have and isolating switch instead of an rcd?

also water pipes in garage are fed from inside house, and they are bonded already inside so do i still need to bond in garage?

if i do need to still bond in garage, can i not just bond the pipes to the new consumer unit as this will create an earth path going back inside?

Yes you do. Once a metallic pipe leaves one building and enters another, it requires main bonding. As this is a PME/TNC-S supply to the house, you can only bond from any extraneous pipework etc, to the garage CU's EMT, if the supplying SWA is a 3 core 10mm or larger. If the supply cable is less than 10mm or only 2 core, then you will need to bring in a separate 10mm main bonding cable from the house MET to the garage EMT, to extend the house equipotential zone in to the garage....

 

[electric will]

The original board has a 6 amp mcb for lighting, with 4 lives coming out of it? I'd want to know where these were going.
and the water heater fault took out a 45 amp mcb? But only when the lights where turned on?
ummmmmmm

 

[Engineer54]

The original board has a 6 amp mcb for lighting, with 4 lives coming out of it? I'd want to know where these were going.
and the water heater fault took out a 45 amp mcb? But only when the lights where turned on?
ummmmmmm

Haha, we don't even know, because the OP has neglected to tell us, what size this SWA cable is, or if it's a 3 core or a 2 core?? All we know is that it's protected by a 45A MCB!!