Surface mounted cabling, regs please

[plugwash]

My gut feeling is with sheathed mains cables you have very little to worry about. I can understand wanting to keep low voltage cables away from unsheathed mains cables (because then you have only a single layer of mains rated insulation) but surely if a cable is safe enough for people to touch it should also be safe enough for low voltage cables to touch it.

 

[ban-all-sheds]

Well, not only is gut feeling not a recognised test method for electrical safety, it's not valid grounds for contravening one of the Wiring Regulations.

 

[stillp]

Well, not only is gut feeling not a recognised test method for electrical safety, it's not valid grounds for contravening one of the Wiring Regulations.

True, but call it instead an "engineering judgement" and it's a valid way of complying with part P.

 

[ban-all-sheds]

If it can be shown that you had the necessary competence to make a valid decision in the matter, and that your decision was a reasonable one.

IMO you would fall at the first fence when asked on what technical data or materials science knowledge you based your decision that the insulation of Cat5 cable was rated at 230V.

 

[stillp]

Why would I need to make a decision about a cable rating BAS? We already know that, generally, there is no insulation rating for the outer sheath of Cat 5E, i.e. the manufacturers don't assign a rating.

I take it you meant to question how I would justify a judgement that the installation of Cat 5E and power cable in a situation where they could come into contact with each other is safe in a specific installation.

I might have decided that since the power cable has reinforced insulation the Cat 5 insulation was sufficient, given its ability to handle 125V without problem. Or I might have assumes (yes, I know) that because the insulation between cores of the Cat 5 withstands 125V, and it is further protected by insulation of whatever thickness it was that I looked up yesterday, and there is little risk of mechanical damage... etc, etc.

 

[ban-all-sheds]

Why would I need to make a decision about a cable rating BAS? We already know that, generally, there is no insulation rating for the outer sheath of Cat 5E, i.e. the manufacturers don't assign a rating.

OK - as you seem to think that that pedantic route leads to a door marked "Way Out" I'll stop saying "rated" and start saying "insulated for", as in "Every cable or conductor is insulated for the highest voltage present"

I take it you meant to question how I would justify a judgement that the installation of Cat 5E and power cable in a situation where they could come into contact with each other is safe in a specific installation.

Yes.

I might have decided that since the power cable has reinforced insulation the Cat 5 insulation was sufficient, given its ability to handle 125V without problem.

And you might be asked, given that the regulations require that every cable or conductor is insulated for the highest voltage present, on what technical data or materials science knowledge you based your decision that because Cat5 cable is able to handle 125V it is insulated for 230V.

Or I might have assumes (yes, I know) that because the insulation between cores of the Cat 5 withstands 125V, and it is further protected by insulation of whatever thickness it was that I looked up yesterday, and there is little risk of mechanical damage... etc, etc.

And you might be asked where the regulation requiring every cable or conductor to be insulated for the highest voltage present contains a clause along the lines of "except where there is little risk of mechanical damage".

 

[stillp]

Why would I need to make a decision about a cable rating BAS? We already know that, generally, there is no insulation rating for the outer sheath of Cat 5E, i.e. the manufacturers don't assign a rating.

OK - as you seem to think that that pedantic route leads to a door marked "Way Out" I'll stop saying "rated" and start saying "insulated for", as in "Every cable or conductor is insulated for the highest voltage present"
That's better!

I take it you meant to question how I would justify a judgement that the installation of Cat 5E and power cable in a situation where they could come into contact with each other is safe in a specific installation.

Yes.
Good

I might have decided that since the power cable has reinforced insulation the Cat 5 insulation was sufficient, given its ability to handle 125V without problem.

And you might be asked, given that the regulations require that every cable or conductor is insulated for the highest voltage present, on what technical data or materials science knowledge you based your decision that because Cat5 cable is able to handle 125V it is insulated for 230V.
But that's only what BS7671 requires. The Building Regs Part P Require the installation to be safe, without specifying how.

Or I might have assumes (yes, I know) that because the insulation between cores of the Cat 5 withstands 125V, and it is further protected by insulation of whatever thickness it was that I looked up yesterday, and there is little risk of mechanical damage... etc, etc.

And you might be asked where the regulation requiring every cable or conductor to be insulated for the highest voltage present contains a clause along the lines of "except where there is little risk of mechanical damage".

But that's only what BS7671 requires. The Building Regs Part P Require the installation to be safe, without specifying how.

 

[ban-all-sheds]

OK - when carrying out electrical installation work which involves the installation of Band I and Band II cables in the same trunking what would you do to ensure that it was safe?