Flying leads and the regulations.

[HandySparks]

Unfortunately it is very flawed. this statement:

"The guidance applies where protection against electric shock is by automatic disconnection of supply, as it is in the vast majority of cases"

made me laugh out loud, as RCD protection is by no means universal. It may exist in the "vast majority" of new buildings. but in the rest it is simply not there! The "vast majority" of the domestic and commercial properties I enter are over 15 years old, and generally still use rewirable fuse protection.

Basically what it says is you can omit a flylead if one of the socket front fixing lugs is fixed, or the box is earthed by SWA or metal conduit and a seperate earth or cpc is connected to the socket front, BUT ONLY IF THE WHOLE IS RCD PROTECTED!!

Are you saying that protection by "automatic disconnection of supply" requires an RCD?

Not true. ADS is the normal means of protection using rewirable fuses, MCBs, etc. See BGB 411.

 

[hermetic]

please quote the relevant passage of BGB 411 whatever that is, as I can find no online reference to it. A rewirable fuse is certainly NOT ADS as far as I am concerned, and if you read my above post, you would see that in the circunstances suggested a rewirable fuse would allow lethal current flow to occur. You are arguing a defenceless point because safety is reduced if the fly lead is omitted, and enhanced if it is fitted. Common sense says it should be there, the problem today is that too many regulations are unclear and conflicting, and common sense is anything but common. I would suggest if your profit margin depends on saving 30 minutes on an entire install by not fitting fly leads, you have misquoted for the job.

 

[HandySparks]

"BGB" is BS 7671:2008 Incorporating Amendment No.1: 2011, Requirements for Electrical Installations. Section 411, "Protective Measure: Automatic Disconnection of Supply".

You do have a copy, don't you?

 

[hermetic]

No, I don't, and never have had, I work to the IEE regs and ammendments, and as you will understand if you have read my above posts, I am not involved in day to day installation any more, so I have no need of one. Neither do I use regulations as an excuse for not thinking. What I do have is a five year apprenticeship at a NICEIC approved contractor from 1967 to 1972, a City and Guilds National diploma in electrical engineering (three years at tech college) and 40 years experience and the certain knowledge that if I had omitted fly leads in socket boxes I would not only have failed my first year at college, I would also have got my backside royally kicked at work. As I have said above, some people will put up with falling standards, some will not. If you have the relevant documentation, please quote from it. I have detailed above the circumstances in which the lack of a fly lead would make an instalation dangerous to an electrician investigating a fault, I stand by it.

 

[rich.250]

The above qouted is actually(or appears to be) guidelines, not regulations. The guidelines say that in certain circumstances, the tail can be omitted, and goes on to list those circumstances. Unfortunately it is very flawed. this statement:

"The guidance applies where protection against electric shock is by automatic disconnection of supply, as it is in the vast majority of cases"

made me laugh out loud, as RCD protection is by no means universal. It may exist in the "vast majority" of new buildings. but in the rest it is simply not there! The "vast majority" of the domestic and commercial properties I enter are over 15 years old, and generally still use rewirable fuse protection.

Basically what it says is you can omit a flylead if one of the socket front fixing lugs is fixed, or the box is earthed by SWA or metal conduit and a seperate earth or cpc is connected to the socket front, BUT ONLY IF THE WHOLE IS RCD PROTECTED!!
However, take the situation where some scumbag hasn't used a grommet in a metal box and the insulation is damaged. When sparky looking for a fault comes along and removes the socket front ,fault clears because the only earth on the box is via the screw, but the box remains live when he restores power to give the sparky a belt when he comes back to it! As I have said in my earlier post ommiting flyleads is just skimping. As professionals , and I am now speaking to the time served properly qualified amongst us, we are supposed to use the IEE regs plus our common sense and experience to produce an installation that is safe in all circumstances. If you need a regulation to back up everything you do,and look for regulations that justify doing less than what will be safe in every circumstance, you are not fit to call yourself an electrician

I have had that exact fault many times, haven't really got time for sloppiness.
Always grommets and tagged boxes, where no fixed lugs.
Most metal boxes I've come across recently don't even have earth terminals......
And as said previously they have the same bs number......

 

[HandySparks]

No, I don't, and never have had, I work to the IEE regs and ammendments, and as you will understand if you have read my above posts, I am not involved in day to day installation any more, so I have no need of one.

Sorry, I hadn't realised that you've been out of the game for a while.

The IEE Wiring Regs became BS7671 at the sixteenth edition. In that edition, the section I refer to is 413-02 "Protection by earthed equipotential bonding and automatic disconnection of supply", and in the fifteenth edition it's 413-2.

 

[hermetic]

Fine, mate, no problem, but I still can't see that a rewirable provides Automatic dissconection, I would want a circuit breaker for that, especially if it was me providing the live to earth path at the other end. As I have said, it is our responsibility according to the (old) IEE regulations to provide an installation that is a safe as it can be in all forseeable circumstances. I personally have never seen socket boxes without earth/cpc/connections, but in this day and age nothing really surprises me.Standards have been alowed to fall dramatically. Don't even get me started on part P!

 

[hermetic]

Also, he said carrying on(LOLS) I would have thought that a fly lead to a back box was a perfect example of "earthed equipotential bonding"

 

[telectrix]

Fine, mate, no problem, but I still can't see that a rewirable provides Automatic dissconection, I would want a circuit breaker for that,

the whole meaning of ADS is nothing to do with RCDs. it's disconnection of supply in the event of a fault. the impedance of the fault path dictates the time taken for the OCPD to operate, whether it be a MCB or a fuse. no OCPD will operate at the sort of level of current that will kill you, that's why we have RCDs AS ADDITIONAL PROTECTION. i do agree with you that fitting flyleads is good practice.

 

[hermetic]

"no OCPD will operate at the sort of level of current that will kill you, that's why we have RCDs AS ADDITIONAL PROTECTION"

Which is exactly what I have said! if there is no RCD, and in my experience installations over twenty years old, and there are millions out there, have no RCD, and will kill you if you become the fault path between an unearthed box that has become live due to insulation damage, and an earthed socket front, if the circuit is only protected by rewirables.

 

[i=p/u]

well we would fail conduit asessments if we didnt have fly leads added, even in all steel conduit circuits.. ...

 

[Geoffsd]

I still can't see that a rewirable provides Automatic dissconection,

automaticadjective (INDEPENDENT)

Definition

An automatic machine or device is able to operate independently of human control

 

[malcolmsanford]

Also, he said carrying on(LOLS) I would have thought that a fly lead to a back box was a perfect example of "earthed equipotential bonding"

In fact it is quite a poor example of bonding, as a fly lead in a back box is earthing

 

[rich.250]

Of course a 3036 rewritable will provide ads. If the circuit complies with the relevant zs for the device. Will still operate in the required time.

I also see a lot of Single boxes for switches with earths in a connector. I see this as worse than not tagging a socket!! Cos at least when the install is finished the screws are earthed.
There not if you don't earth the box on anything rated below ten amps
It Seems.........

 

[rich.250]

Rewirable. Stupid phone.

 

[hermetic]

"In fact it is quite a poor example of bonding, as a fly lead in a back box is earthing"

Please explain your understanding of the differences between earthing and bonding as they apply within an installation final sub circuit as opposed to at incoming supply connection.

 

[telectrix]

my interpretation is that you earth exposed conductive parts and bond extraneous conductive parts.

 

[hermetic]

Yes Rich250, I got your meaning, and you are quite correct that the rewiarable will blow in the case of a direct short type fault to earth depending on the Ze. However, if the fault path from a live untagged back box to earth is via the body of some poor sparky, sufficient current will flow to kill him without the fuse blowing, which was my initial premise. We have already had a comment to say that someone has seen this fault "many times"

 

[hermetic]

The guidance from BS given above says that although in most circumstances a back box cannot be touched it is still classed as "exposed" and therefore must be earthed.
Bonded to what? if not to earth then to other extraneous metalwork? what is the point of that? If it is not ultimately bonded to earth then its potential can rise above that of earth (be it a spike, pme, transformer tapping or whatever), hence the term Equipotential bonding. I agree fully with the point about switch boxes by the way.

 

[Deleted member 26818]

We are required to earth exposed-conductive-parts.
It is generally accepted that this earthing can be achieved by means of the 3.5mm screw and a fixed lug.
Where socket-outlet back boxes, are concealed in walls, they are not necessarily exposed.
Earthe Equipotential Bonding, or Main Protective Bonding (as it is now known) would only be required, if the socket-outlet back box is considered an extraneous-conductive-part.