Using cpc as neutral

[johnduffell]

‘Or Immediate proximity’ I read as 6491 singles in conduit or trunking taking the same complete route as both or all lives. This is in order to terminate at each accessory.

Interesting didn't think about that re wiring systems:, so if two 3 core flexes routed together you could do it in one of them but not if they went via different routes? Or is that only if they are in the same containment rather than being sheathed?
That's more strict then i was originally thinking.

 

[Rpa07]

@johnduffell you call it strict - I call it safe, as all installations should be.
We all need to sleep at night and installing safely to regulations, that are set in place for a reason, make my pillow feel like a cloud!

 

[johnduffell]

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@johnduffell you call it strict - I call it safe, as all installations should be.
We all need to sleep at night and installing safely to regulations, that are set in place for a reason, make my pillow feel like a cloud!

I meant strict in the mathematical sense of more tightly defined, not in the sense that i disagreed with it.
Anyway thanks for helping!

 

[Colin33]

Hi - I'm struggling to think of installing a circuit without a cpc. Some have been installed historically, but I don't think that's been since the '60s. As I've started to practice for the regs exam ( ) the two regs I could find that seem relevant are 543.6.1 and 543.2.9 .

Not so long ago I was wiring up an underfloor heating system. The controls for the heating were all downstairs, along with domestic hot water controls. The zone valves, along with the water tank and gas boiler were all in the loft. To complicate things, there was also a solar thermal input and a 'warm loop' system. I had a twin n earth cable feeding the system and supplying a large junction box with its cpc. I also had two 5 core flex going up to the JB in the loft. Therefore, I had two green/yellow cores which were not required as a cpc. I did need to use one of these as a live conductor and oversleeved it at each end accordingly. Isn't this an example of when an unused cpc is legitimately used as a live conductor?

 

[davesparks]

Not so long ago I was wiring up an underfloor heating system. The controls for the heating were all downstairs, along with domestic hot water controls. The zone valves, along with the water tank and gas boiler were all in the loft. To complicate things, there was also a solar thermal input and a 'warm loop' system. I had a twin n earth cable feeding the system and supplying a large junction box with its cpc. I also had two 5 core flex going up to the JB in the loft. Therefore, I had two green/yellow cores which were not required as a cpc. I did need to use one of these as a live conductor and oversleeved it at each end accordingly. Isn't this an example of when an unused cpc is legitimately used as a live conductor?

No, that’s an example of very poor workmanship, the correct cables should have been installed for the job.

Where were the 5 core cables coming from? Did that point not need a cpc?

 

[johnduffell]

junction box with its cpc. I also had two 5 core flex going up to the JB in the loft

So based on the discussion so far, whether it's within the regs depends whether the pair of flexes are run together in close proximity.

the correct cables should have been installed for the job

Youre assuming in your assertion that those are not the correct cables. According to the earlier discussion, as long as the cables are in close proximity it looks like they are correct.

Where were the 5 core cables coming from? Did that point not need a cpc?

He said the large junction box, which had a cpc:

twin n earth cable feeding the system and supplying a large junction box with its cpc

 

[Adam W]

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I meant strict in the mathematical sense of more tightly defined, not in the sense that i disagreed with it.
Anyway thanks for helping!

Yes. All of the figures we work to were calculated by the boffins at the IET and are given for a reason - the maximum Ze on a particular system, minimum CSA of cables, maximum tripping times, touch voltage, CSA of bonding conductors... They don't just pluck figures out of thin air for you to come along and decide it's easier to make a deviation.

As far as I'm concerned the electronics inside my mobile phone works by means of witchcraft, I mean I have absolutely no idea how it works, it's like electronic circuits and that. I don't need to know how it works and I'm not really going to benefit from doing a degree in electronics just so that I can say I understand how it works, the explanation of 'witchcraft' is good enough for me as long as I can make phone calls and send texts.
Same with the maths in the regs book - just because you don't understand it doesn't mean you can deviate, in fact that's more of a reason not to, but for the purposes of pulling in circuits you need to accept that the figures work.

 

[elsparko]

Not so long ago I was wiring up an underfloor heating system. The controls for the heating were all downstairs, along with domestic hot water controls. The zone valves, along with the water tank and gas boiler were all in the loft. To complicate things, there was also a solar thermal input and a 'warm loop' system. I had a twin n earth cable feeding the system and supplying a large junction box with its cpc. I also had two 5 core flex going up to the JB in the loft. Therefore, I had two green/yellow cores which were not required as a cpc. I did need to use one of these as a live conductor and oversleeved it at each end accordingly. Isn't this an example of when an unused cpc is legitimately used as a live conductor?

a yellow/green sleeved conductor should only be used as a cpc, i think the regulations are pretty cut and dry on this subject

 

[johnduffell]

a yellow/green sleeved conductor should only be used as a cpc, i think the regulations are pretty cut and dry on this subject

True but when he said "oversleeved accordingly" presumably that wouldn't be oversleeved green yellow over green yellow insulation

 

[Toneyz]

We all know he means oversleeve with brown or blue sleaving to use it as a live or neutral.

 

[Toneyz]

We all know he means oversleeve with brown or blue sleaving to use it as a live or neutral.

I was hoping that the idiots that were using a CPC in a T&E/3 core and E cable as live or neutral had well and truly gone from the profession.

 

[elsparko]

True but when he said "oversleeved accordingly" presumably that wouldn't be oversleeved green yellow over green yellow insulation

and what happens when that brown or blue oversleeve falls off the green yellow core of the flex and someone assumes that naturally its an earth for something?

multicore exists for a reason, this reason.

 

[Rpa07]

and what happens when that brown or blue oversleeve falls off the green yellow core of the flex and someone assumes that naturally its an earth for something?

multicore exists for a reason, this reason.

In any situation, that is where voltage indicators come into the part of our job @elsparko - assuming makes an ‘Aaargh that wire is live!’

 

[elsparko]

In any situation, that is where voltage indicators come into the part of our job @elsparko - assuming makes an ‘Aaargh that wire is live!’

its still not to be used as a live conductor, oversleeving or not.

 

[Rpa07]

That’s not what you implied though @elsparko was it? Safety first, the world second!