Why do we do it the way we do in the UK?

[Electrics]

I can sense a picture coming.

Lol nah i'm a trainee without an employer, trying to get as much info as i can to the many hundreds of questions i have ?

 

[telectrix]

my thinks......average house.RFC for kitchen, rest of sockets on 2/3 20A radials.

 

[Electrics]

my thinks......average house.RFC for kitchen, rest of sockets on 2/3 20A radials.

That's what i woulda thought - is it true that you're only allowed one radial per 50sqm area? I've heard this said but struggling to find the rule written down.

I thought RFC for the kitchen just because of the load being drawn if eg toaster, kettle, dishwasher and washing machine are all on at the same time.

 

[pc1966]

That's what i woulda thought - is it true that you're only allowed one radial per 50sqm area? I've heard this said but struggling to find the rule written down.

There is no rule as such, just some guidance for "typical" usage. From memory it is 50m^2 for 20A radial, 75 for 32A radial and 100 for 32A RFC.

Recent tradition is one floor of a house would be on a RFC. More recently came the idea of one just for the kitchen as more power-hungry accessories came in to common use.

In truth the RFC is very robust, many place have everything on one and it is just fine. the more recent trend for more separate radial socket circuits in the UK is probably driven more by RCDs and accumulated leakage.

I thought RFC for the kitchen just because of the load being drawn if eg toaster, kettle, dishwasher and washing machine are all on at the same time.

I would agree. Some prefer 4mm radials but that is marginal if much thermal insulation, and by 6mm it is hard to wrnagle or fit pairs in to socket terminals..

But more often than not the main issue/guidance that seems relevant is separate single sockets per appliance, not doubles that seem to burn out more.

In Scotland the building regs say there must be accessible means of isolation for white goods, so you probably would have an RFC around 20A DP switches and each running 2.5mm to an unswitched socket behind the appliance, etc.

 

[Simon47]

By the way, SBS make one....
I've been thinking about trying one when I find the right job for it.

Yes, they are nice boxes, and he's very flexible.
Also does some nice glands. The 25mm tail set he does fits in a 32mm hole, and there's an adapter if yo have a 40mm hole. The last one I got from the wholesaler (CEF) was 40mm an by the time you added an adapter down to 32mm it was a horrible monstrosity.

 

[pc1966]

Yes, they are nice boxes, and he's very flexible.
Also does some nice glands. The 25mm tail set he does fits in a 32mm hole, and there's an adapter if yo have a 40mm hole. The last one I got from the wholesaler (CEF) was 40mm an by the time you added an adapter down to 32mm it was a horrible monstrosity.

CEF appear to do a 32mm one, though the image does not seem to match as it does for the 40mm one:

32mm Plastic Cable Gland LSF with Multiple Insert, Locknut and Blanks IP68

Flame protection Glow wire test 750° C acc. to EN 60695-2-11

www.cef.co.uk

40mm Plastic Cable Gland LSF with Multiple Insert, Locknut and Blanks IP68

Flame protection Glow wire test 750° C acc. to EN 60695-2-11

www.cef.co.uk

They also stock the Wylex one but at quite a price:

32mm Plastic Cable Gland with Multiple Insert and Locknut

Moulded cable gland kit for metal consumer unit to provide additional support and supplementary insulation similar to Class II construction for the incoming cables

www.cef.co.uk

 

[Mikegh]

Its all DP 2-mod rcbos here

Takes up more space ,.main boards are always at least ,2-row

Better job on an rcbo board to be breaking both live poles for a fault I reckon

 

[Mike Johnson]

As I understand it, the double pole RCBO's only monitor the Phase side, the neutral side is just dragged along on a fault condition, so as you say it does break both.

 

[Mikegh]

As I understand it, the double pole RCBO's only monitor the Phase side, the neutral side is just dragged along on a fault condition, so as you say it does break both.

You mean the MCB side of it ?

It'll be just on the L pole

 

[pc1966]

Its all DP 2-mod rcbos here

Takes up more space ,.main boards are always at least ,2-row

Better job on an rcbo board to be breaking both live poles for a fault I reckon

You can get DP RCBOs in single width, like the compact Wylex, Crabtree, and fusebox RCBOs so they take no more space then traditional UK style MCBs.

I really prefer DP ones for various reasons:

• They isolate both L & N so you can IR test the circuit without having to unscrew anything
• If you have a TT style arrangement with an up-front delay RCD the you don't trip that on a N-E fault downstream (as N is isolated)
• If you are really unfortunate and have reversed polarity, you still get some hope of a fault being interrupted (but you really don't want to test that out as the I2t of the relatively slow RCD opening action will be horrendous)