CU Cable Bunching..?

[jon557]

Hi,

Quick question that has been baffling me, I have seen many CUs whereby the cables enter shared entry points. Does this not mean the cables are now bunched according to the regs? And this all cables should have been calculated with the capacity drop? Or is a CU entry just a bit pedantic for that?

The Victorian house I am working on at the moment has all the cables coming through one hole in the ceiling to the CU also, so I guess the same issue there. I have made separate holes for my work though.

Just wondered what people do about this. I read a lot on this forum about regs but also common sense - as if you can't always follow all the regs to the letter because sometimes you have to make a safe and common sense judgement call on a unique installation.

Cheers.

 

[Ian1981]

Not all circuits require a grouping factor to be applied.
Circuits/cable grouping factors are based on the assumption that all cables in a group are carrying rated current. If a cable is expected to carry no more than 30% of its grouped rated current, it can be ignored when calculating the group rating factor.
It’s more for fully loaded cables/circuits.
Cables spaced at twice their diameter away can also be ignored.
See appendix 4 for more details

Put it this way, I rarely install 4mm ring final circuits and 1.5mm lighting circuits in domestic installations based on grouping.

 

[Toneyz]

Ninja Sparky has put an excellent well-explained post/video on his youtube channel well worth a look at. I don't think an inch or two is going to detrimental.

 

[Timbo]

Ninja Sparky has put an excellent well-explained post/video on his youtube channel well worth a look at. I don't think an inch or two is going to detrimental.

Funny, I was just looking at that on my phone.

 

[jon557]

Great thanks guys. I asked a STROMA assessor about this too and he said it was fine, the regs are more concerned with bunching cables in a run. I wish the regs would put some extra detail around stuff like this. I follow a few sparks on Youtube, Thomas Nagy is my favourite.

I just checked and I have seen a few of SparkyNinja's videos, one about making CU's look neat - basically saying don't cable tie within the CU, space them if possible. Makes sense.