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

Electrics · Aug 27, 2021

Was just watching a video of an RCBO install and found it weird that the breakers are double pole yet still have to have a fly lead.

Why don't we do it like this:

Ignore the gibberish coming out of his mouth and take a look at the unit. L+N coming from the supply, feeding the bottom of the first RCD. All the RCD's are linked together by the linking bars running down the left, giving them all L+N feed. The feed then goes through the RCD out the top, into the bus bar that's linked across the tops of all the MCB's. The L+N of each circuit comes out the bottom. This does away with the need for a neutral bar (there is one but they are used when there is no linking bar employed and you have to run an N to each RCD), several main neutral cables and the need to fill the unit with loads of extra cabling, not to mention cost saving on the materials.

Why, even with dual pole RCBO's, do we still make them use fly leads when we could simply link them all to N via the main RCD in? Makes no sense to me.

Having said that we're still the only country i know of that uses rings.

Anyone think we'll eventually catch up and stop doing things in such weird ways? Although i guess one drawback of the way they do it in Europe is that their multi tier units are standard for almost any regular sized home and they are anywhere from £3-700.

pc1966 · Aug 28, 2021

Simon47 said:
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 · Aug 30, 2021

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 · Aug 30, 2021

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 · Aug 30, 2021

Mike Johnson said:
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 · Aug 30, 2021

Mikegh said:
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)

Mikegh · Aug 30, 2021

pc1966 said:
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)

Can you get a L+N busbar for the single width ?

Mike Johnson · Aug 30, 2021

Mikegh said:
You mean the MCB side of it ?

It'll be just on the L pole

?

loz2754 · Aug 30, 2021

Mikegh said:
Can you get a L+N busbar for the single width ?

Yes. Crabtree and SBS make such a consumer unit.

Mikegh · Aug 30, 2021

Mike Johnson said:
?

I must have misunderstood your post then

Simon47 · Aug 30, 2021

Mike Johnson said:
Mikegh said:

You mean the MCB side of it ?
It'll be just on the L pole

Click to expand...

?

It's one of those "you need to check" things. I expect the some of the two module types will sense (MCB function) on both poles, and some of the single module types don't even switch the neutral.
Some of the single module types sense on the L pole only (for the MCB function) but switch both poles. Obviously for the RCD function they sense on both poles.

LastManOnline · Aug 30, 2021

Mikegh said:
Its all DP 2-mod rcbos here

The DP 2 mod rcbo, s with L and N busbar fed from underneath is undoubtedly one of the best designed and user friendly DB, s that's ever hit the market. It really should be the "gold standard". However, after 25 years of using them I, m sad to say, there appears to be a change on the way. (over here in ROI). Have you seen the latest Hagar designed DB based on the new 2021 regs?

Mikegh · Aug 30, 2021

LastManOnline said:
The DP 2 mod rcbo, s with L and N busbar fed from underneath is undoubtedly one of the best designed and user friendly DB, s that's ever hit the market. It really should be the "gold standard". However, after 25 years of using them I, m sad to say, there appears to be a change on the way. (over here in ROI). Have you seen the latest Hagar designed DB based on the new 2021 regs?

No, I'm familiar with the changes to DBs in the new rules here, but haven't seen the Hager board

LastManOnline · Aug 30, 2021

Mikegh said:
No, I'm familiar with the changes to DBs in the new rules here, but haven't seen the Hager board

Mikegh · Aug 30, 2021

LastManOnline said:
The DP 2 mod rcbo, s with L and N busbar fed from underneath is undoubtedly one of the best designed and user friendly DB, s that's ever hit the market. It really should be the "gold standard". However, after 25 years of using them I, m sad to say, there appears to be a change on the way. (over here in ROI). Have you seen the latest Hagar designed DB based on the new 2021 regs?

What's actually in the Hager board

We're very similar to the UK now non-, combustible boards, arc fault and surge protection

Heading towards all rcbo although I think it's only a recommendation

They can't seem to think straight on bathroom lighting ,went ott with emergency lighting and rcbos and now they're allowing it on a shared rcd if I'm not mistaken

LastManOnline · Aug 30, 2021

I install this tomorrow. First rewire under new regs. To my great surprise the single module rcbo and the "dreaded flylead" has invaded our shores. Our beloved 2 pole rcbo and L +N busbar is being sacrificed for space in preparation for rcbo populated DB, s.