Earth rings on SWA cables

[jamie-spark]

However, should the cable tray be installed in such a manner that it is lekely to introduce a potential from outside the location, thereby meeting the definition of an extraneous-conductive-part, then main equipotential bonding will be required (Regulatiuon 413-02-02 refers). For example, consider a run of cable tray carrying services into a particular building. The cable tray may be in contact with the earth potential ouside a building and upon entering into the building would be likely to introduce the earth potential into that building. In such a case the tray would warrant the defintion of an extraneous-conductive-part and consequently main equipotenial bonding would be required.

as i said if it was classed as an extraneous conductive part it would require bonding. if it is not then no bonding required

 

[jamie-spark]

Dillb mate

Yes i am happy leaving metal work that is neither extraneous or exposed conductive parts unbonded/earthed. just like when i have put up double insulated metal fittings, with BS and the double square markings i have not decided to earth them to be on the safe side

heres why
Exposed-conductive-part.Conductive part of equipment which can be touched and which is not normallylive, but which can become live under fault conditions.
Extraneous-conductive-part. Aconductive part liable to introduce a potential, generally Earth potential, andnot forming part of the electrical installation
A cable tray or a cable basketwhere used as a support and cable management system has to be considered in thecontext of earthing and bonding. In other words, are such systems, whereconsisting of metal and plastic-coated metal, exposed-conductive-parts orextraneous-conductive-parts and consequently do they require earthing orbonding?
Addressing, first, the questionof earthing and whether the cable tray or basket should be earthed, electricalequipment such as cables mounted on a metallic support system will normally beequivalent to either a Class I construction (for example copper sheathed,mineral insulated cables without an overall PVC covering) or a Class IIequivalent construction (for example PVC insulated and sheathed cable).
Exposed-conductive-parts ofcables, such as the copper sheath of a mineral insulated cable, are required tobe connected to the MET of the installation by a CPC designed to conduct earthfault currents. The cable tray or basket which the mineral insulated cable isattached to, or may be in contact with, is not itself anexposed-conductive-part and therefore it does not require earthing. To do sowould only serve to distribute further any touch voltage resulting from anearth fault on an item of equipment to which the cable is connected.
A cable complying with theappropriate standard having a non-metallic sheath or a non- metallic enclosureis deemed to provide satisfactory protection against both direct and indirectcontact, as does an item of Class II equipment (Regulation 471-09-04 refers).Class II equipment is constructed such that any insulation fault in the cablecannot result in a fault current flowing into any conductive parts with whichthe equipment may be in contact. Hence, the metal cable tray or basket need notbe earthed

as above

 

[somersetsparks]

I always thought that tray should be bonded, I Remember doing my AM2 and having to bond the tray, basket, especially with T+E could become live with snagged cable etc, however it is usually connected to earth via the main frame of the building anyways.

With regards to the article above, it mentions tray being used as a protective conductor, I have always thoght this was not allowed?

 

[jamie-spark]

I always thought that tray should be bonded, I Remember doing my AM2 and having to bond the tray, basket, especially with T+E could become live with snagged cable etc, however it is usually connected to earth via the main frame of the building anyways.

With regards to the article above, it mentions tray being used as a protective conductor, I have always thoght this was not allowed?

When i sat my fica we got told to supplementry bond the tray too, were told dont ask questions just do it

 

[somersetsparks]

When i sat my fica we got told to supplementry bond the tray too, were told dont ask questions just do it

Your dead right, best not to rock the boat when being tested! I don't know the right or wrong of this one im afraid, your presenting me with logical reasons but something just tells me it should be bonded!

 

[jamie-spark]

Your dead right, best not to rock the boat when being tested! I don't know the right or wrong of this one im afraid, your presenting me with logical reasons but something just tells me it should be bonded!

we were told dont question it dont leave it or you will loose points
At the end of the say its up to us as installers to decide . I just read as much as i can fit in, to try an gain knowledge as to why to do it or why not. some people still say bond sinks or metallic furniture in kitchens ect ect cos its what they have done for donkeys and they will continue to do so i suppose

 

[Guest55]

... some people still say bond sinks or metallic furniture in kitchens ect ect cos its what they have done for donkeys and they will continue to do so i suppose

Then those people dont understand why they are doing something , or what constitutes an extraneous conductive part.

 

[jamie-spark]

we are reading of the same page

 

[somersetsparks]

I can see a tray load of SWA's or MICC wouldnt need bonding unless it met the definitions of an ECP, however if it was a basket full of twins I would be tempted to, however most of the trays/baskets I have seen pick up very good connections to earth through purlings/ RSJ's etc. Whether they then need bonding is doubtful I suppose, as they are reliably connected to earth.
I have been on jobs as part of the 'earthing squad' though and have had to bond acroos every piece of racking and framework with 70mm links though, however different systems are in place on these jobs and they are often not to BS7671

 

[Deleted member 26818]

Getting back to the banjos.
If the manufacturer's instructions indicate that banjos should be used, then they become a requirement of the Reguations.

 

[Plonker 3]

That can be a major problem though, how often do you gland a SWA off but give the instructions to the final user? Or for most other items thinking about it. I know things like fans, light fittings you should but certain things just get thrown away once finished with.

 

[telectrix]

i was always under the impression that banjos were for the express purpose of fitting fly leads, e.g. when using non metallic enclosures. with metal enclosures and no requirement fo fly leads, then the banjo serves no useful purpose.

 

[mheyes]

I seem to remember that BICC made a SWA gland that had serrated edge. It did NOT ship with a earth ring. That was many years ago, I would code it a C3 myself.

 

[Engineer54]

i was always under the impression that banjos were for the express purpose of fitting fly leads, e.g. when using non metallic enclosures. with metal enclosures and no requirement fo fly leads, then the banjo serves no useful purpose.

Still need a banjo or Piranha earthing nut with fly lead, if connecting a SWA or similar to a metal enclosure with bolted gland plates Tel.

 

[aprillove1719]

i agree..:yes:

 

[gpe]

ECA inspector would pull it as a non conformity, the one thing you have to meticulous about is the bonding, SWA cables with an integral earth have to have the sheath bonded and I am sure that the carcase of the DB would not be good enough for an inspector.

 

[Engineer54]

ECA inspector would pull it as a non conformity, the one thing you have to meticulous about is the bonding, SWA cables with an integral earth have to have the sheath bonded and I am sure that the carcase of the DB would not be good enough for an inspector.

WHY NOT??

It always has been in the past, though i must admit i've always used serrated lock nuts when fixing to metallic enclosures...

 

[sparkymalarky]

Would it not be better practice to use bolted rings and earthing lugs and take a fly lead off the bolted ring and terminate along with the circuit CPC? Guarantees continuity of the armouring as you also have a secure gland to the fixture or accessory.

 

[Engineer54]

Would it not be better practice to use bolted rings and earthing lugs and take a fly lead off the bolted ring and terminate along with the circuit CPC? Guarantees continuity of the armouring as you also have a secure gland to the fixture or accessory.

Piranha serrated lock-nuts combine both facilities, a biting surface and fly-lead terminal...

 

[sparkymalarky]

Ah handy!