CU Layout / Circuits

[Nickfromwales]

Yup. Doing my bedrooms all on radials. Work in progress . @Onoff will know what I mean. ?

[Nickfromwales]

55 minutes ago, PeterW said:

Right... had a quick rework and based on a 21 way unit I've ended up here..

 

Just so we are aware, that boiler run is about 4 ft in the same room btw as this is all in the plant "cupboard"...

 

Ah! Ok, Same room = oky-doky.

Seems good to go. ? U/S sockets on a ring is plenty good enough TBH. Just going radial in mine so I can knock rooms off individually. Cable runs are a breeze too that way. 

[Steptoe]

I just think radials are much better, 

Less inconvenience under fault,

Less cable,

Less labour

Safer

Why have a cable that can only carry 27a (under ideal conditions) when you don't need to,?

Tip of the day, why the smokes are on us lights,?

Feed to ds smoke, 3c to upstairs smoke, t&e to us lights from us smoke, less cable, less labour, 

 

 

Oh, and again, do NOT use SP RCBOs, 

[Nickfromwales]

24 minutes ago, Steptoe said:

Oh, and again, do NOT use SP RCBOs, 

Spill the beans Harold. ? I don't see the advantage of DP TBH. 

[Steptoe]

8 minutes ago, Nickfromwales said:

Spill the beans Harold. ? I don't see the advantage of DP TBH. 

SP RCBOs don't disconnect the neutral,

You can in effect end up with a daisy chain of a N-E fault on one circuit still leaking across the other circuits even when that RCBO has tripped,

Causing other RCBOs to trip also.

Not common, granted, but, I've come across it twice in the past ten years, also, SP doesn't, imho, comply if it is TT,

Switching off a SP RCBO also doesn't imo comply with isolation of a circuit,

 

SP RCBOs are a half ars*d method of thinking you are doing something better than fitting a dual or triple RCD unit.

 

Oh, and don't get me started with what happens if you end up with a reverse polarity on the incomer, it does happen,!!!!!

 

Edited January 23, 2017 by Steptoe

[Nickfromwales]

6 minutes ago, Steptoe said:

Switching off a SP RCBO also doesn't imo comply with isolation of a circuit,

 

What about with any mcb loaded board? Same thing

 

6 minutes ago, Steptoe said:

SP RCBOs are a half ars*d method of thinking you are doing something better than fitting a dual or triple RCD unit.

 

Multi-RCD units still wipe out numerous circuits in one go. Can't really agree with that PoV TBH as I think they're a vast improvement. 

True circuit isolation can easily be achieved by knocking the isolator off imo, plus anyone messing around with this should examine the rcbo type before undertaking any work anyhoo. 

This could go on a bit

 

[Steptoe]

Yep, agreed @Nickfromwales

But with a DP RCD when a fault trips, its isolated, and won't daisy chain every other circuit off, so perhaps less inconvenience, ?

And, TBH, DP RCBOs are available at reasonable cost, 

I can actually source them for comparable price to control gear SP RCBOs, so its a no brainer not to use them , IMO.

Yep, you could turn off the isolator to isolate, but you lose everything, working on upstairs lights, turn off RCD on that circuit, plug your handlamp into upstairs sockets, simples, working on upstairs sockets, turn RCD off and upstairs lights still work.

 

[Nickfromwales]

I was going to brew some fresh coffee and keep at you, but just remembered I'm up at 6 to load the kids brekky into the catapult ?  

Nos Da!

 

[Ferdinand]

@PeterW

 

If you are on a dual board (ie two banks with individual "offs") then consider distributing your ring circuits, your two ovens and your showers across the two - so that you still have the ability to cook and use power when someone is working on the other half.

 

Ferdinand

[Steptoe]

Its only an opinion @Nickfromwales

formed from years of using them long before the UK caught onto the benefits of them, same as RFCs, no one but UK (in reality) uses them as they are outdated too,

Personally I only ever use SP RCBOs in very particular circumstances,

But I most definitely would never recommend anyone using them in a self build, why save £100 on a >£50K job?

Edited January 24, 2017 by Nickfromwales
Edited to remove 'safety' comment

[Steptoe]

Just now, Ferdinand said:

@PeterW

 

If you are on a dual board (ie two banks with individual "offs") then consider distributing your ring circuits, your two ovens and your showers across the two - so that you still have the ability to cook and use power when someone is working on the other half.

 

Ferdinand

He's using all RCBOs, so no 'banks' as such

[Ferdinand]

1 minute ago, Steptoe said:

He's using all RCBOs, so no 'banks' as such

 

OK.

 

However, I have all RCBOs (albeit dodgy single ones ) *and* banks :-).

 

F

Edited January 23, 2017 by Ferdinand

[Steptoe]

3 minutes ago, Ferdinand said:

 

OK.

 

However, I have all RCBOs (albeit dodgy single ones ) *and* banks :-).

 

F

Errrm, I'm confused as to how you could possibly have (or why) you would have banks of RCBOs, or do you have a double decker board,? Or some other strange install,,,,,,,

Edited January 23, 2017 by Steptoe

[Ferdinand]

Just now, Steptoe said:

Errrm, I'm confused as to his you could possibly have (or why) you would have banks of RCBOs, or do you have a double decker board,? Or some other strange install,,,,,,,

 

I will start up that other thread ... but yes it is double decker.

[Steptoe]

1 minute ago, Ferdinand said:

 

I will start up that other thread ... but yes it is double decker.

Ah, OK, its sort of half normal to have 2 isolators, although you should still have one main switch that kills everything, 

Edited January 23, 2017 by Steptoe

[Ferdinand]

Just now, Steptoe said:

Ah, OK, its sort of half normal to have 2 main switches, although you should still have one main switch that kills everything, 

 

I bet I have one of those as well, as I normally try and get one done immediately my side of the meter.

[Steptoe]

Just now, Ferdinand said:

 

I bet I have one of those as well, as I normally try and get one done immediately my side of the meter.

Yep, its fairly common now to have them fitted,

REC2 or 2S for single phase.

 

[joe90]

On 22/01/2017 at 16:52, Steptoe said:

Are you using Double Pole RCBOs, ?

Oh, and I'd have the smoke alarms on with one of the lighting circuits, just a personal preference of mine.

 

 

I really like this idea and will be incorporating it into my house build, hallway light I think.

[Onoff]

Some consider having the fridge/freezer on it's own RCBO. Idea being that something on the kitchen "ring" going when you're away doesn't ruin loads of food.

[Jeremy Harris]

These choices all come down to being informed, working out your own personal risk tolerance and weighing these up with cost and convenience, together with the potential gotchas in some installations.

 

For example, I have a 10 way CU, filled with SP RCBOs.  Despite it being a big box (in terms of depth), there is not a lot of free space in there.  If it had DP single width RCBOs then I think it would be pretty stuffed, just because of the volume of wire, the SP ones are bad enough.

 

Yes, it's very convenient to isolate a single circuit to work on it using a DP RCBO.  Yes there is a tiny degree of additional protection from a couple of pretty rare fault events from using DP RCBOs.  However, is it a major safety enhancement over using all SP RCBOs, with a higher rated DP RCD as a main switch?  Not in my view.  It's certainly better, but it's not the sort of step-change in safety we got when we first introduced RCDs. 

 

And, just as  benchmark, our existing house, built around 1982/83, has no RCD, no MCBs, but wired fuses and a single DP isolator.  In the 16 years we've lived here we've never had a fuse blow, or a wiring problem, and the house passes the periodic safety checks and tests I do with no problems ever showing.

 

In terms of safety, a standard split box, with two RCDs and bunch of MCBs is actually pretty good, and a massive enhancement over the system I have in our old house.  Is an all SP RCBO CU any better?   Not in terms of safety, but yes in terms of user convenience.  Is an all DP RCBO CU an enhancement in safety?  By  minuscule amount, realistically.  It's big advantage is the convenience of DP isolation of each circuit for maintenance, and that's probably a good enough reason to do it.

 

It's a bit like other risks we accept.  Every planning decision I've ever seen has included a comment from a fire officer about the effectiveness of sprinkler systems and that fitting them should be a planning recommendation.  However, very few people seem to take heed of that, and in my view, fire is a far greater risk to life now in a domestic situation than an electrical fault.

 

 

[Steptoe]

15 hours ago, JSHarris said:

These choices all come down to being informed, working out your own personal risk tolerance and weighing these up with cost and convenience, together with the potential gotchas in some installations.

 

For example, I have a 10 way CU, filled with SP RCBOs.  Despite it being a big box (in terms of depth), there is not a lot of free space in there.  If it had DP single width RCBOs then I think it would be pretty stuffed, just because of the volume of wire, the SP ones are bad enough.

 

Yes, it's very convenient to isolate a single circuit to work on it using a DP RCBO.  Yes there is a tiny degree of additional protection from a couple of pretty rare fault events from using DP RCBOs.  However, is it a major safety enhancement over using all SP RCBOs, with a higher rated DP RCD as a main switch?  Not in my view.  It's certainly better, but it's not the sort of step-change in safety we got when we first introduced RCDs. 

 

And, just as  benchmark, our existing house, built around 1982/83, has no RCD, no MCBs, but wired fuses and a single DP isolator.  In the 16 years we've lived here we've never had a fuse blow, or a wiring problem, and the house passes the periodic safety checks and tests I do with no problems ever showing.

 

In terms of safety, a standard split box, with two RCDs and bunch of MCBs is actually pretty good, and a massive enhancement over the system I have in our old house.  Is an all SP RCBO CU any better?   Not in terms of safety, but yes in terms of user convenience.  Is an all DP RCBO CU an enhancement in safety?  By  minuscule amount, realistically.  It's big advantage is the convenience of DP isolation of each circuit for maintenance, and that's probably a good enough reason to do it.

 

It's a bit like other risks we accept.  Every planning decision I've ever seen has included a comment from a fire officer about the effectiveness of sprinkler systems and that fitting them should be a planning recommendation.  However, very few people seem to take heed of that, and in my view, fire is a far greater risk to life now in a domestic situation than an electrical fault.

 

 

A board filled with DP RCBOs will actually be a lot neater and tidier than SP ones due to LESS cables inside, and, they can be got in same form factor as an MCB.

Edited January 24, 2017 by Nickfromwales
Edited to remove comment regarding own equipment and testing.

[TerryE]

14 hours ago, Steptoe said:

You might disagree with JSH, but is what he's saying really dangerous?   He's essentially deferred to domain professionals like -- or not like -- yourself.  If your want to have a debate and win it in the view of other members then please present evidence-based information. 

 

Edited January 24, 2017 by Nickfromwales
Edited to remove deleted quote

[Jeremy Harris]

14 hours ago, Steptoe said:

A board filled with DP RCBOs will actually be a lot neater and tidier than SP ones due to LESS cables inside, and, they can be got in same form factor as an MCB.

 

I'm just trying to put some balance into what is a debate about appropriate levels of safety, from my personal perspective.  There can never be absolute safety, and that's the point I'm making here.  Risk appetite and safety are very variable, and no two people will perceive things in the same way, which is a pretty good thing, otherwise we'd all be pretty dull.

 

Risk must be be assessed by the individual, with the benefit of information from as many reliable sources as possible, if they are making their own choice about something that offers better, or just different, protection than the minimum required by regulation. 

 

All I've ever done here is say what my personal view is.  It's not wrong, it's not against any regulation, and in my view it's a small improvement on a split board.  You have a different personal view, that's fine by me, I've never once stated that you are wrong, either.  We are all entitled to an opinion, and holding a different one is not an offence.

 

Do the current electrical regulations state that you have to fit an all DP RCBO board?

 

Do they state that fitting an all SP RCBO board is hazardous? 

 

No, the current recommended minimum acceptable standard is a CU with two DP RCDs controlling two separate sections with MCBs for each circuit within each section.  The "clever" people say that's good enough for all of us, not me, I'm not one of the clever people, and I ceased to be an IEE member over a decade ago, just before the merger that formed the IET.

 

When it comes to setting safety standards that have to be enforced, then that's done by a committee of clever people, who sit down, weigh up the facts, look at the accident and incident statistics over the last few decades, balance those with cost and consumer impact and produce a set of balanced regulations. 

 

It seems you don't agree with all of those regulations, and as it happens I don't either, but in a different way.  That doesn't make me right and you wrong, or vice versa, it just means we have a different view as to where the balance lies between risk, safety, the probability of an incident happening, the types of incidents that are common, the types that are less common, convenience, cost etc.  There's nothing at all wrong with that.  I'm not saying, and have never, ever, said, or implied that, "my way is the only safe way" of doing anything.  It's up to people reading and researching to form their own views and make their own decisions.

Edited January 24, 2017 by Nickfromwales
Edited to amend content according to previous edits / quotes

[Steptoe]

The IEE or IET do NOT make any regulations that anyone has to follow, BS7671 is non statutory,

EAWR is STATUTORY however, and those are what we must work to,

Jeremy, its not intended as a direct 'go' at you, it is merely intended to prevent people making erroneous judgements that may lead them to having a dangerous or unsafe electrical installation.

 

OK, so back to EAWR, you can download it for free as its a statutory document,

A few quick ones you may wish to look at, 

Reg 16 : probably the one regulation I quote more than any other,

its self explanatory.

 

A few others worth a look, 

BTW, its not a big book if you just get the guidance version, so well worth a read,

Reg 3  part 57-60

Reg 4(3)

Reg 5 part 86

 

Edited January 24, 2017 by Nickfromwales
Irrelevant content removed

[Jeremy Harris]

 

 

I didn't state that the IEE/IET as it is now make the regulations at all, neither did I imply that they did, I just mentioned that I used to be a member of the IEE years ago, nothing to do with regulation making.

 

What I actually wrote, and you've quoted, from your quote of my own words, with regard to making regulations was this:

 

12 hours ago, Steptoe said:

When it comes to setting safety standards that have to be enforced, then that's done by a committee of clever people, who sit down, weigh up the facts, look at the accident and incident statistics over the last few decades, balance those with cost and consumer impact and produce a set of balanced regulations. 

 

I don't disagree with any of the regs you quote, but if you're going to be critical about me, then please make the effort to be accurate about what I have written, rather than misinterpret something.

 

Edited January 24, 2017 by Nickfromwales
Irrelevant content removed