Split Load CU

[BillyMac]

Seen the MK CU from screwfix that comes with all the MCB's in. Is there any reason why I couldn't put a second RCD in and have three blocks of mcb's (fixed/rcd1/rcd2)???

 

[plugwash]

yeah it doesn't have a third neutral bar

the largest mc enclosure (21 ways total 17 left for mcbs when fitted out as a split) does have a third neutral bar but is hard to get and expensive

 

[ban-all-sheds]

Why do you want 2 RCDs?

 

[BillyMac]

I was thinking of separating out the lighting circuits from the ring main, so they're both protected and I'll always have some lights. Or my other thought was to separate upstairs and downstairs onto separate RCD's.

Is this a seriously dumb idea? I just like safety and feel happier having more, not less, on RCD protected circuits.

 

[ban-all-sheds]

You don't need the lights on an RCD circuit, and if you want to go down the route of fine-grained protection for your installation, the way to do it is to have a non-RCD board (unless you've got a TT supply), and use RCBOs.

 

[BillyMac]

BAS

You don't need the lights on an RCD circuit

So what happens when someone sticks their fingers in the light socket without RCD protection, or screws a floorboard through a lighting cable?

Don't they just get fried?

 

[plugwash]

you are supposed to check for cables before screwing down floorboards
and anyway as long as the cuiruit is properly designed hitting the earth wire should trip the mcb

as for sticking your fingers in a lampholder (which you shouldn't do anyway and is pretty damn hard to do by accident) you are only touching not grabbing something live which means generally you will survive it

the biggest danger at mains voltage is your hand clamping onto the live part and being unable to let go

 

[ban-all-sheds]

BAS

You don't need the lights on an RCD circuit

So what happens when someone sticks their fingers in the light socket without RCD protection, or screws a floorboard through a lighting cable?

Don't they just get fried?

Or crosses the road without looking.

Or grasps a knife by the shiny bit.

Or drinks bleach.


There's only so far you can go to guard against idiocy.

With the light socket, they'd touch Live and Neutral, not earth, so an RCD would do bu**er all anyway.

With the floorboards, if the cables are installed according to the regulations, a screw can't reach them.