Wiring a Garage consumer unit.

I just emailed them via their website and told them as much. Couldn't help chuckle that they'd got a 'captcha' form on the email submission - presumably to reduce spam. The irony!

How do you ensure the fault current is between 30 mA and 100mA? If you touch the live and earth and conduct 120 mA wont both trip anyway?

Do you have a quicker trip on the 30mA one????

You can get the front cover off most CUs without turning off the main switch. The real work of art is removing or adding MCBs without turning the power off. Removing MCBs is usually harder than fitting them when the power is on.

You've drawn two phase (live) conductors leaving the CU but only one neutral conductor returning to the CU.

Your qualified electrician can't join the neutrals somewhere in the garage and run one neutral back to the CU. The two circuits leaving the CU have to be kept separate from each other and must return to the CU on their own neutrals. (Wiring reg 314-01-04.)

You can't. The fault current is whatever it is.

Yes. If you have a 30 mA RCD fed via a 100 mA RCD then the 100 mA RCD needs to be a time-delay version. If you have an earth leakage fault the local 30 mA RCD should then trip without tripping the house

A typical TT install would have a type S (time delayed) trip on the upstream RCD.

The problem with that is a 100mA delayed trip will kill a significant percentage of the population. Even the 30mA quick trip is not 100% safe.

On Thursday 13 February 2014 08:09 dennis@home wrote in uk.d-i-y:

The 100mA RCD is not there to act as an RCD in the usual sense (eg save your life when you pick up a wet cut mower flex). It is there to achieve the required disconnection times in the event of an earth fault AND a poor earth (eg TT system).

It's also providing fire protection (for phase to earth faults that aren't large enough to trip the overcurrent protection).

it's going to take the electrics out, which further up the line has a chest freezer on it.

the point of the insulation shroud, if there is a pin to get a shock from?

Tim

Well since he started this little job in 2014, one must assume if Mark doesn't reply................

The shroud is a nicety - to reduce the contact area should you need to work while some other circuits are powered.

However, for this example of 2 breakers, and I woudl say, for any domestic case, there is not reason at all you should be working in a CU with a live busbar.

I would not cut the spare off - you may need to add a new breaker one day. It's quite safe when the enclosure is on.

I've seen instructions for things like this in the past, and they've said 'cut off the excess busbar'.

What do people think of wrapping the excess in insulating tape? Or shrink-wrap tubing?

If it's a secondary CU in a garage, presumably anyone sensible would find it easy enough to isolate at the primary CU before working on it? Let Darwin have a chance at the rest ...

Pointless mostly.

Tape - no. if you use the way, your prong is now covered in sticky stuff.

Heatshrink - tricky unless you do it before you install the bar.

A bit of heavy sleeve that is a tightish fit would be OK if you really want to.

This job was done a year ago. If he did go back & follow your advice, he'd create a rough sharp edge & conductive swarf. Tinsnips are way quicker.

NT