SWA Earthing

[telectrix]

a query. If wiring to a sub, e.g. in a garage in SWA, using 1 core as earth, armour is earthed at supply end. My question is--- is there any reason not to also earth armour to the earth core at the sub end

 

[ezzzekiel]

what would be the point if its already earthed

 

[telectrix]

agreed, just a belt and braces one. i use the SWA locking earth nuts, so no need for banjos, seems a pity to waste the nut's earthing facility

 

[malcolmsanford]

If you agree with the theory that by earthing both ends you could create fields, eddies and all sorts then definately no ............and still no if you don't subscribe to that theory

 

[Gravid]

Is it not considered just good practice?

If you agree with the theory that by earthing both ends you could create fields, eddies and all sorts then definately no ............and still no if you don't subscribe to that theory

Out of interest what is that theory ?

 

[malcolmsanford]

You not heard it whispered in dark corners that if a fault occurs and you connect both ends of a SWA you will create eddy's.

It's the same theorists that all bonding conductors should be kept tight as if there is a fault and 100's amps go down the condutor it can whiplash ...................

I must go to some wierd places

 

[Gravid]

Hahaha does sound wierd! I'll keep my ears open.

 

[telectrix]

malcolm, i bow to your superior knowledge

 

[malcolmsanford]

malcolm, i bow to your superior knowledge

Well not sure about superior ......................just if you do this electric thing long enough chances are you have messed the something up that someone wants to know about

 

[benji]

This type of thread has been going on for years personally i will allways gland both ends wether i insulate one end would be on the instructions of a qual.elect.engineer ,but it would be informative to get a definative answer from the IEE on where and what to do.

yours gb

 

[telectrix]

i am a qualified elect. engineer and i don't know the answer

 

[mechelec]

Im not sure that eddy currents will flow in the event of a fault in a multicore armoured cable as the protection will clear the fault in such a short time that the eddy currents will not have time to establish and cause damage ie heating. Also if one core is being used a sthe earth then it is enclosed within the magnetic armour and will be cancelled out. I d know that single core cables with non magnetic sheaths should have the sheath bonded at one end only as during normal service eddy currents can flow and cause heating of the cable if both ends are bonded.

 

[davelerave]

can anyone help clarify this re: earthing at both ends on multicore swa


say both ends were glanded to metal boards-wouldn't it be best to fit the flylead anyway

 

[malcolmsanford]

If I was bonding both ends of a SWA that for me would mean that I'm using it as the CPC and therefore I would banjo and fit fly earths both ends