Rings or Radials ....

[Octopus]

Just started on a complete refurbishment / extension on a 3 bedroom property which is having a complete rewire.

I'm not keen on Dual RCD boards, nor trying to have as few circuits as possible ....

So when it comes to the socket circuits I was thinking of:

Radial 20A for hall, lounge and dining room
Ring 32A for kitchen
Radial 20A for upstairs

Anyone like to comment?


PS the plumber was asking me today why I was installing 35 mm boxes - he seemed to think 25 were always best!

 

[Midwest]

I can get a 10way lewden/control gear board with 8 RCBO's for £99

My local wholesaler only stocks MK, Wylex and some Hager stuff, unfortunately.

 

[Midwest]

Are you chasing the walls with a jack hammer or something?

The internal walls on a local residential estate (circa 1985), which I do a fair bit of work on, are made up of three pieces of 12mm plasterboard, stuck to each other

 

[Midwest]

well yeah unless you want the whole board tripping in the event of a neutral-earth fault...RCBO trips, as it's solid neutral the neutral isnt disconnected so takes out the upfront time delayed RCD.

My memory is a bit hazy, but I recall the 18th draft mentioning something about this subject? Guess division of installation would still have to be considered.

 

[stevethesparks]

Tried my fist SBS DP rcbo board this month, and am quite pleased with it. Mine was on a TT system, and I used a time delayed 100mA RCD as the main switch. The install was made easier and looked neat without all the wandering tails and functional earth leads from the rcbo's. Good price and quick delivery.

 

[suffolkspark]

if you've got TT you can fit a full RCBO board and LEAVE the 100A DP switch upfront unchanged.

if you've got a dual RCCB board, that is when you need to change the upfront 100A DP to a 100mA type S.

 

[Adj]

35mm boxes always - but the the dot and dab boys don't half cuss when I don't sink them in.

 

[Leesparkykent]

My local wholesaler only stocks MK, Wylex and some Hager stuff, unfortunately.

Change wholesaler ....I get them from Electric centre. My local branch stopped stocking MK as everyone moaned about them. On the shelf they now keep Hager and Lewden.

 

[sam400]

if you've got TT you can fit a full RCBO board and LEAVE the 100A DP switch upfront unchanged.

if you've got a dual RCCB board, that is when you need to change the upfront 100A DP to a 100mA type S.

What’s the thinking behind this?

Cheers

 

[suffolkspark]

What’s the thinking behind this?

Cheers

In a dual RCCB board you have the brown and blue link leads between the main switch and the RCCB's and neutral bars IF any of these were to come adrift or melt or be nibbled, and come into contact with the metal, then the only protective device is the service head fuse, and on TT you can be pretty sure you wont have a low enough Zs to allow enough current to flow to blow it so it will just sit there live all day long. in this instance the 100mA type s gives those internal link wires fault protection, and also maintains discrimination from your 30mA RCCB's.

With a full RCBO board there are none of these internal links so no need for upfront protection, and as somebody mentioned if you use single pole RCBO's and DO fit an upfront 100mA type S RCCB, you havn't got discrimination as the neutral will be left in circuit if the RCBO trips which could trip the 100mA.

In both instances a gland should be used on the incoming tails.

 

[Toneyz]

The internal walls on a local residential estate (circa 1985), which I do a fair bit of work on, are made up of three pieces of 12mm plasterboard, stuck to each other

I remember those walls nightmare for installing boxes.

 

[stevethesparks]

if you've got TT you can fit a full RCBO board and LEAVE the 100A DP switch upfront unchanged.

if you've got a dual RCCB board, that is when you need to change the upfront 100A DP to a 100mA type S.

Just belt and braces approach as was so cheap

 

[bigspark17]

In a dual RCCB board you have the brown and blue link leads between the main switch and the RCCB's and neutral bars IF any of these were to come adrift or melt or be nibbled, and come into contact with the metal, then the only protective device is the service head fuse, and on TT you can be pretty sure you wont have a low enough Zs to allow enough current to flow to blow it so it will just sit there live all day long. in this instance the 100mA type s gives those internal link wires fault protection, and also maintains discrimination from your 30mA RCCB's.

With a full RCBO board there are none of these internal links so no need for upfront protection, and as somebody mentioned if you use single pole RCBO's and DO fit an upfront 100mA type S RCCB, you havn't got discrimination as the neutral will be left in circuit if the RCBO trips which could trip the 100mA.

In both instances a gland should be used on the incoming tails.

Theres still a tail from main switch to N bar, i will still fit rcd td upfront on TT

 

[suffolkspark]

Theres still a tail from main switch to N bar, i will still fit rcd td upfront on TT

Nothing wrong with that at all as long as your RCBO's are 2 pole.

 

[Dave OCD]

Has anyone ever seen a meter tail or internal link actually become detached and cause a short ? Not only would it have to come out of the terminal/cage clamp it would also have to move considerably. About as much chance of me winning the lottery.

 

[suffolkspark]

Nope, its all overkill like a lot of our regs to be fair