1mm 2c+e vs 2.5mm single core earth
If I had a circuit without an earth and replaced a fitting with one that needed one I would always run an earth, that's not the question here, the question is is it compliant to run a 1mm 2c+e and only use the earth to earth the fitting?
I personally would always run a 2.5mm single core but someone suggested they used 1mm 2c+e
Under 5.5.2.2.1 I understand the earth can come from another circuit and initially I felt this applied to using the 1mm 2c+e but then it got me thinking because if the P and N aren't connected then it's just as much a different circuit as it is the same circuit and really it's no circuit at all because P and N aren't connected
I'll still continue using a 2.5mm single core myself but just curious if using a 1mm 2c+e is actually compliant in this situation and if anyone can express any thoughts
Earthing lights with existing 2 core
Re: Earthing lights with existing 2 core
I don't believe using the 1 mm2 PEC of (for example) a 2C+E cable - other cores not used - complies with the intent of the rule.
As for the letter; go though step by step.
5.5.2.2.1 says the PEC of one circuit can't be used for earthing items supplied from another circuit
The Exception then says that you can use a an unenclosed common PEC for a number of different circuits
So the overall effect is that you can't use a PEC that's included in the cable of any circuit apart from the one supplying the item concerned.
So clearly a separate PEC from item concerned, to any point permitted by 5.5.2.1, is compliant;
2.5 mm2 being the minimum size for an unenclosed PEC as per 5.3.3 / Table 5.1 (assuming active conductor not > 6 mm2).
I suspect the idea of using a 1 mm2 core came from Table 5.1; which suggest that 1 mm2 (or 1.5 mm2) can be used as ling as its "incorporated in a multi-core cable". However Table 5.1 isn't a standalone thing, its part of clause 5.5.3 that sets minimum size of earthing conductors. So we have to read the whole clause to see whether the proposed method is compliant.
I can't see any of the (bold text) fundamental requirements of 5.3.3.1.1 that would not be met.
5.5.3.1.2 permits compliance with Table 5.1 as one option (and calculation as the other); but there are some Ecxceptions to be worked through as well. Exception 3 says the earthing conductor in a cable must comply with 5.3.3.4. That subclause says the minimum for a single-core cable is 2.5 mm2, and the minimum for a multicore cable is 1 mm2. So from all that the proposed method appears to be compliant with the letter of the rules; provided the un-used cores are correctly terminated as per 1.5.11.4.
Depending on specific pricing; there may also be a (small) price advantage; but I don't accept that it an be classed as good trade practice. In my view it's just a deliberate attempt to avoid complying with a rule.
As for the letter; go though step by step.
5.5.2.2.1 says the PEC of one circuit can't be used for earthing items supplied from another circuit
The Exception then says that you can use a an unenclosed common PEC for a number of different circuits
So the overall effect is that you can't use a PEC that's included in the cable of any circuit apart from the one supplying the item concerned.
So clearly a separate PEC from item concerned, to any point permitted by 5.5.2.1, is compliant;
2.5 mm2 being the minimum size for an unenclosed PEC as per 5.3.3 / Table 5.1 (assuming active conductor not > 6 mm2).
I suspect the idea of using a 1 mm2 core came from Table 5.1; which suggest that 1 mm2 (or 1.5 mm2) can be used as ling as its "incorporated in a multi-core cable". However Table 5.1 isn't a standalone thing, its part of clause 5.5.3 that sets minimum size of earthing conductors. So we have to read the whole clause to see whether the proposed method is compliant.
I can't see any of the (bold text) fundamental requirements of 5.3.3.1.1 that would not be met.
5.5.3.1.2 permits compliance with Table 5.1 as one option (and calculation as the other); but there are some Ecxceptions to be worked through as well. Exception 3 says the earthing conductor in a cable must comply with 5.3.3.4. That subclause says the minimum for a single-core cable is 2.5 mm2, and the minimum for a multicore cable is 1 mm2. So from all that the proposed method appears to be compliant with the letter of the rules; provided the un-used cores are correctly terminated as per 1.5.11.4.
Depending on specific pricing; there may also be a (small) price advantage; but I don't accept that it an be classed as good trade practice. In my view it's just a deliberate attempt to avoid complying with a rule.
Re: Earthing lights with existing 2 core
It's certainly interesting because I agree I feel like it's not the intent but couldn't deliberately fault it
I feel like it may not just be cost driven but may be a case of, I have 1mm 2c+e on me but not 2.5 single core
If the P and N where terminated into the same protective device and N bar for that circuit then this would be compliant because it would then become the same circuit, if terminated to another circuit it no longer would as it'd be a different circuit but the fact of not terminating either doesn't make it a circuit at all, does it? So that's what threw me off
I feel like it may not just be cost driven but may be a case of, I have 1mm 2c+e on me but not 2.5 single core
If the P and N where terminated into the same protective device and N bar for that circuit then this would be compliant because it would then become the same circuit, if terminated to another circuit it no longer would as it'd be a different circuit but the fact of not terminating either doesn't make it a circuit at all, does it? So that's what threw me off
Re: Earthing lights with existing 2 core
Yes, if using the N-bar to safely terminate the un-used red & black conductors; would have to use the same terminal as the N of the actual circuit.
I think this would be a better option than simply putting them into a connector and not labelling them; which would be the minimum to comply with 1.5.11.4 at the switchboard end.
I think this would be a better option than simply putting them into a connector and not labelling them; which would be the minimum to comply with 1.5.11.4 at the switchboard end.