by ericmark »
Sun Aug 07, 2022 10:05 pm
There seems to be a requirment for a single point isolation, but never found the regulation, likely fire or building regs, rather than BS 7671.
It has been said the DNO should provide an isolator, but it seems very rare to find that, again not BS 7671 but HSE who require the electrical supply to be isolated else where, to the board your working on, and unless there is an isolator, you could only do this by drawing the DNO fuse, and two wrongs don't make a right.
Usually the way forward is to get an isolator fitted, then who ever does the work can do it dead.
As to where to take supply from, I would personally use either a MCB or RCBO, even if a 45 amp one.
But first question is how your going to earth the new garage. So your looking at design, there is an IET wiring matters about wiring out buildings, a bit dated, but free down load and worth a read.
Distance between building matters, not just your buildings but any other which may have metal outside bonded to the supply which you can touch at same time as some metal on your building.
I would aim today to make a garage TT if possible to make EV charging easier in the future.
But I could only decide that after visiting the site, basic it is a risk assessment, no right or wrong, the advent of the double pole single width RCBO has made it easier, I would not today consider a double RCD consumer unit, it would be all RCBO, but go back 20 years, and we did not have that option, so many people have to work with less than ideal equipment.
So design is not always simple, and whoever does the design has to sign the installation certificate to say they did the design, and although the forms can have three signatures, the forms used by the scheme providers only have one, so you would need to go through LABC.
The cost of using LABC can get silly, it depends on what you have, when I looked at doing my mothers house I estimated it would cost between £500 and £1000 to get the test equipment and pay LABC to DIY, and so although an electrician I decided it was cheaper to pay some one else to do the job.
I would suggest you get a quote first, then decide if DIY is worth while, and likely they will say how they would do the job so gives you some pointes.
