S.W.A. Armour Earthing.

gkenyon:

AJJewsbury:


We are a bit double standarded (is that a word?) though - on one hand we claim the sheath isn't an adequate insulator, but then when we create a TT island we typically rely on the sheath (and boot over the gland) to prevent contact between two different earthing systems (which under some conditions can differ by full mains voltage).

I don't agree that a "boot" over the gland does the job in the case that the armour is not earthed as an exposed-conductive-part or protective conductor. Suitable insulation such as cold shrink sleeving (that can only be removed by destruction - Regulation 416.1), is far more appropriate, and indeed the actual requirement of BS 7671.


Think about the fact that the person you are trying to protect isn't just someone who is neither skilled nor instructed, but perhaps the "next spark in the queue" ... and the fact that the EAWR and CDM Regs apply in almost all circumstances to the work being undertaken by that person, or the designer or both ... and if you decided to take that approach, you're the designer.

I was thinking more of the situation where the armour/gland is Earthed - but to a different Earthing system to the one in area it is located in. As far as I recall guidance metions the possibility of glanding into an insulating enclosure but with no mention of replacing the usual boot with adhesive lined heat shrink.


Indeed the whole subject of insulation between Earthing systems seems rather lacking.


  - Andy.

gkenyon:

AJJewsbury:


We are a bit double standarded (is that a word?) though - on one hand we claim the sheath isn't an adequate insulator, but then when we create a TT island we typically rely on the sheath (and boot over the gland) to prevent contact between two different earthing systems (which under some conditions can differ by full mains voltage).

I don't agree that a "boot" over the gland does the job in the case that the armour is not earthed as an exposed-conductive-part or protective conductor. Suitable insulation such as cold shrink sleeving (that can only be removed by destruction - Regulation 416.1), is far more appropriate, and indeed the actual requirement of BS 7671.


Think about the fact that the person you are trying to protect isn't just someone who is neither skilled nor instructed, but perhaps the "next spark in the queue" ... and the fact that the EAWR and CDM Regs apply in almost all circumstances to the work being undertaken by that person, or the designer or both ... and if you decided to take that approach, you're the designer.

I was thinking more of the situation where the armour/gland is Earthed - but to a different Earthing system to the one in area it is located in. As far as I recall guidance metions the possibility of glanding into an insulating enclosure but with no mention of replacing the usual boot with adhesive lined heat shrink.


Indeed the whole subject of insulation between Earthing systems seems rather lacking.


  - Andy.