metal Cu earth straps

[Lurch]

Otherwise they are not bonded once the screws are removed.

But you shouldn't be removing them without isolating them first so there shouldn't be an issue there. I know everyone does so I totally understand where you're coming from.

 

[Slowhand]

But you shouldn't be removing them without isolating them first so there shouldn't be an issue there. I know everyone does so I totally understand where you're coming from.

I know mate but it's more for the DIYers and clueless have a go at fixing it people.

The ones who take a switch or socket off without isolating it and poke about with a neon screwdriver

regardless of and or oblivious to the dangers that working with electricity may bring.

If you think about it what's the point of bonding it if its buried in a wall and not having it bonded when exposed and with live conductors waving about?

I'm about to stand away from the laptop and put my tin hat on.

 

[Lurch]

If you think about it what's the point of bonding it if its buried in a wall and not having it bonded when exposed and with live conductors waving about?

Well if you start applying to logic to the regs you soon come unstuck! There's lots of regs I subtly ignore in one way or another, as I'm sure others do for various reasons. I can pretty much guarantee that we will all do things slightly differently. One thing I don't do though is things 'just in case someone clueless comes poking about in it'.

 

[Slowhand]

Well if you start applying to logic to the regs you soon come unstuck! There's lots of regs I subtly ignore in one way or another, as I'm sure others do for various reasons. I can pretty much guarantee that we will all do things slightly differently. One thing I don't do though is things 'just in case someone clueless comes poking about in it'.

I understand where you're coming from but I've been bonding metal backboxes since 1974 and nobody yet has given me a good reason why I should not do it.

The same goes for putting cables in tubing or capping instead of clipping them direct to a wall that's going to be plastered.

 

[binky]

I read the Control Gear instructions today....



this was far more disturbing though....define continuous!

 

[phil d]

I read the Control Gear instructions today....

View attachment 7948

this was far more disturbing though....define continuous!

View attachment 7949

Years ago you didn't group mcb's as you do today, whereas now you start at the right and run say 45A,32A,32A 32A, 20A,16A,10A,6A,6A, years ago you'd run say 45A, 6A, 32A, 6A, and so on, the idea being that by not placing 2 high load breakers side by side you shouldn't get any appreciable heat build up.

 

[Tony S]

Years ago you didn't group mcb's as you do today, whereas now you start at the right and run say 45A,32A,32A 32A, 20A,16A,10A,6A,6A, years ago you'd run say 45A, 6A, 32A, 6A, and so on, the idea being that by not placing 2 high load breakers side by side you shouldn't get any appreciable heat build up.

Lumping all the higher rated MCB’s together doesn’t assist heat dissipation. Space them high/low in alternate succession.

High to low working away from the intake is yet another electrical myth!

 

[binky]

I tend to insert MCBs according to how cables drop into board, ie fairly random. What shocked me was the 60% derating. Has anyone seen similar info from other manufacturers?

 

[Sidewinder]

Pretty common derating across the board from the OEM's I believe.

From Schneider, unofficially, and not just theirs, but others they have tested:  The EM field from a highly loaded MCB adjacent to an RCD can, and will affect the RCD response time in the event of a fault.

 

[Tony S]

Justification of interspersing MCB ratingg

 

[Rob_the_rich]

Whilst fitting a board yesterday I was considering the need for the earth strap included for the front cover. Given that we earth metal back boxes via the cover screws, and I don't think I've ever seen earth straps on 3 phase boards, and that the metal front is secured by metal screws to the metal back back panel (which cuts through any paint), then the question is 'are these straps actually needed?'.

The front covers usually have a drop-down flap which would be held up by the householder when re-energizing a tripped mcb/rcd. The extra bonding, I assume, is provided by the OEM to try and mitigate the effects of holding on to a bit of metal connected to the earth when doing so. Hopefully, electricians would use a magnet, insulating tape or vde screwdriver to hold up the flap, householders won't though.

 

[binky]

if it has shorted to the casing, there is a serious fault.....

 

[Rob_the_rich]

if it has shorted to the casing, there is a serious fault.....

I was thinking more of the Earthing conductors carrying a fault current for the period of time it takes for the re-energised mcb/rcd to re-trip, and the householder completing part of the earth fault path.

 

[steptoe]

if it has shorted to the casing, there is a serious fault.....

You'd think!!!!!

I removed the cover from a metal cu once to find the incoming Line conductor sitting freely in thin air,!

Couldn't have been much more than 1/2" from the cover, if even that!

Then saw a 2.5 going into the Line side of the main switch, after closer inspection I then saw the bit of 2.5 stuck behind the incoming side of the meter and going to the main switch,!!!! 

baddayexplode

 

[Andy™]

itll be fine, especially on a TT system where the RCD in its plastic insulating enclosure will will operate and trip the power. oh wait, nevermind

 

[Rob_the_rich]

TNCS with broken PEN?

Someone will die from this sooner or later, who will be in the dock? LFB? IET? Me?

 

[ProDave]

TNCS with broken PEN?

Someone will die from this sooner or later, who will be in the dock? LFB? IET? Me?

What is your concern here? Have you ever been in a house with a broken PEN?  It's spooky. Yes the case of the metal CU must have risen to near phase potential, so why didn't I get a shock from it? Why hadn't the customer complained that anything he touched gave him a shock? because the whole house was floating at phase potential, that's why. The only complaint was "no power"

 

[binky]

so how have we survived working with 3 phase boards for years?

 

[Tony S]

so how have we survived working with 3 phase boards for years?

Knowledge, practical skills and a total disregard of stupid health & safety rules.

 

[ProDave]

so how have we survived working with 3 phase boards for years?

or "old" metal domestic CU's? (or even fuse boards)