2 core cable..

[Crosswire]

When supplying an item of double insulated equipment, (in this case an extract fan). Is it acceptable to use a two core cable i.e. no cpc?

Or is the earth still required in order to protect the cable run?

 

[Octopus]

If you are refering to a cable through a wall or in a wall no as there is a reg stating that a CPC should be taken to each point.

If you are referring to a "flying lead" out of a FCU then maybe you could do it but I wouldn't

 

[Marvo]

I'm not UK based so I don't know the regs but I would say it was good practice to continue the cpc in the cable to give the RCD a chance at offering effective protection in the event of cable damage occurring.

 

[Crosswire]

If you are refering to a cable through a wall or in a wall no as there is a reg stating that a CPC should be taken to each point.

If you are referring to a "flying lead" out of a FCU then maybe you could do it but I wouldn't

I have never done it either, but the question came up at work, and I wondered if it was acceptable as the equipment is double insulated..

I don't suppose you know the Reg by any chance?

 

[Deleted member 26818]

Yes it is acceptable.
No the CPC unless it is in the form of a sheath or armour is not required to protect the cable run.

 

[Crosswire]

I'm not UK based so I don't know the regs but I would say it was good practice to continue the cpc in the cable to give the RCD a chance at offering effective protection in the event of cable damage occurring.

Sounds like sensible reasoning.

The back story is that one of our testers refused to pass an installation due to 2 core being used for the fans. He met with resistance and arguments, and I just wondered if he was 'technically' right. The fact that it is good practise is beyond question imo.

 

[Crosswire]

Yes it is acceptable.
No the CPC unless it is in the form of a sheath or armour is not required to protect the cable run.

Interesting.... So maybe the tester was wrong on this occasion?

 

[Marvo]

Surely if the tester failed it because of no CPC then he should be able to back up his decision with a regulation???.

 

[MDJ]

I think from memory in 412. something or other there is a mention that double insulation need not have an earth but a earth free labell should be fixed near to an enclosure where connections are made, something like that anyhow, and go easy, it is from memory lol.
wheres my hard hat haha

 

[Octopus]

Yes it is acceptable.
No the CPC unless it is in the form of a sheath or armour is not required to protect the cable run.

411.8.5 ?

412.2.3.2 ?

Still think its good practice to always have a CPC and that's what I was taught

 

[MDJ]

I haven't got my BGB on my fella, whats the reg say?

 

[Crosswire]

Surely if the tester failed it because of no CPC then he should be able to back up his decision with a regulation???.

Yeah , you would think so..........

However, no reg was mentioned when he told me the story. I held my tongue until I could be sure whether he was correct or not. He just said it was needed to "protect the cable" (his words).

 

[Geoffsd]

412.2.3.2

 

[MDJ]

Geoffsd, whats the reg say fella, please don't make me go to my van in the cold to find out :furious3:

 

[Deleted member 26818]

He's probably taking the last paragraph of 411.3.1.1: "A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a lampholder having no exposed-conductive-parts and suspended from such a point." out of context.
He needs to first consider the first paragraph of 411.3.1.1: "Exposed-conductive-parts shall be connected to a protective conductor under the specific conditions for each type of system earthing as specified in Regulations 411.4 to 6."

If there are no exposed-conductive-parts, then there is no requirement to connect them to a protective conductor, and no requirement to run and terminate that protective conductor at each point etc.

Regulation 411.8.5 is in relation to reduced voltage (110V), not low voltage.
Regulation 412.2.3.2 is in relation to the possible use of a CPC at some point in the future, not in relation to protecting the run of the cable.

Considr this, a bell transformer sited fairly close to a CU.
Would you run a CPC from the CU to the transformer if there is no earthing terminal at the transformer?

 

[Crosswire]

412.2.3.2

412.2.3.2 Except where Regulation 412.1.3 applies, a circuit supplying one or more items of Class II equipment shall have a circuit protective conductor run to and terminated at each point in wiring and at each accessory.

 

[MDJ]

okay I'm going to the van huh

 

[Octopus]

412.2.3.2 Except where regulation 412.1.3 applies, a circuit suppling one or more items of Class II equipment shall have a circuit protective conductor run to and terminated at each point in wiring and at each accessory

Still think its good practice to always have a CPC available.

 

[MDJ]

Just flicking through now fella, looks like your right unless I spot a small reg hiding under another somewhere haha, my feet are cold now as well lol, I ran out to the van with no socks on

 

[Crosswire]

Just flicking through now fella, looks like your right unless I spot a small reg hiding under another somewhere haha, my feet are cold now as well lol, I ran out to the van with no socks on

That's dedication dude!

 

[Octopus]

Yet another daft example of the regs.

Why don't they simply say that all circuits from a distribution board must have a continuous CPC run to each and every accessory??

 

[Crosswire]

So in summary it seems that

"412.2.3.2 Except where Regulation 412.1.3 applies, a circuit supplying one or more items of Class II equipment shall have a circuit protective conductor run to and terminated at each point in wiring and at each accessory."

supercedes "411.3.1.1"

and thus the tester was correct on this occasion?

 

[MDJ]

yep dedication, basically it is about time a decent chat was on here by sparks discussing a reg or 2, after having a good look through, I think murdoch is right, reg 412.2.3.2 looks like the reg which suggests it is required, still looking for the hidden one though.

 

[Geoffsd]

412.2.3.2 Except where Regulation 412.1.3 applies, a circuit supplying one or more items of Class II equipment shall have a circuit protective conductor run to and terminated at each point in wiring and at each accessory.

That's it - with the note that it is intended to take account of the possible replacement by the user of class II equipment by class I equipment.

The proviso of 412.1.3 relates to whole installations of class II under supervision so that no changes will be made - plus a bit more.


Edit - I type too slow.

 

[Deleted member 26818]

If you for instance were to run a cable with no joins, directly from a CU to to a double insulated item of equipment, how many points in the wiring requiring a CPC to be connected would there be?
If no accessories are used in the circuit (remembering that an item of current using equipment is not considered to be an accessory) where would you connect a CPC?