Two supplies, one cable- Regs?

[tee-eff-ten]

I have always been of the opinion that this was not specifically dis-allowed as long as the cable rating etc was correct and everything identified properly. To be more specific we're talking about 2x SP mcb's in a board using two cores for each circuit in a 4c cable, splitting at a junction box to feed two motorised doors. I'm only asking as this has come up as a C1 on an EICR and, although it's been a while since I completed one of these myself it seems a bit over zealous! Thoughts welcome.

 

[snowhead]

Was there a Reg quoted with the C1?

 

[Lucien Nunes]

Not aware of any problems with that in itself. We often do it in theatre lighting with six or eight circuits run in one cable, because of the large number of identical circuits that often travel the same routes. I can envisage situations where confusion or maintenance difficulties might occur, such as cables terminated within current-using equipment. An unrelated circuit would be a complete surprise, difficult to isolate and removal for maintenance would disable the other circuit, in which case I would code it according to which problem(s) it creates.

As for the coding - if something they perceive (rightly or wrongly) to be a bit naughty merits a C1, I wonder how they code a busbar chamber with no cover?

 

[timhoward]

It's certainly not disallowed in general. There are general instructions how to handle it.

The regs for sharing/sizing CPC apply, but I would expect these to be met in most scenario's involving SWA.

I've always wondered about cable rating for this precise scenario - as I don't believe the standard tables cover the scenario of two single-phase circuits where all 4 cores are carrying more current. I'm aware of Table 4B5 but don't think it helps as it starts with "5 loaded cores".
But that's more of an academic question - obviously two motors won't be on together for very long while both doors open or close together.

 

[tee-eff-ten]

Was there a Reg quoted with the C1?

No. As the site electrician of a sizeable industrial enterprise I have 10 pages of observations presented by an external contractor with no reg numbers in sight! I think firms these days use software with pre installed phrases, but this is no help to a recipient like me trying to decipher and correct the supposed deviations.

 

[westward10]

There is nothing wrong with doing this provided the conductor insulation is rated for the highest voltage present. It is no different to multiple circuits contained in a single conduit.

 

[tee-eff-ten]

As for the coding - if something they perceive (rightly or wrongly) to be a bit naughty merits a C1, I wonder how they code a busbar chamber with no cover?

Don't know but thankfully we don't have one of those...