Short tails

[Pete999]

Hi
I've heard lots of talk on forums regarding what one person described as the three meter rule, with regard to the size of cable required, (for example a 500a busbar sysem, and a requirement for a smaller supply taken from these busbars) should the cable from the busbars to the new switch gear, be the same as the feeders into the busbars? I appreciate it may be a bit difficult to understand my ramblings. It's a bit like spurring off of a RFC to a FCU in 2.5mm2. Hope this clear enough for a response.I can't find any reference to this in BS 7671.

 

[ChrisElectrical88]

:-/ that makes zero sense to me

 

[Plonker 3]

No, spoke to NICEIC tech support regards this. Reg 434.2.1 refers to this as does page 51 of GN6.

 

[Baker1988]

Im sure the 3 meter rule is only for supply cable from the meter to the main distribution board I also think it only applys in domestic

 

[Pete999]

got it baaggered if I could find that cheers again

 

[Badged01]

No, spoke to NICEIC tech support regards this. Reg 434.2.1 refers to this as does page 51 of GN6.

Got the BGB so can see what 434 advises but havent got GN6. Could you summise what page 51 suggests?

 

[Plonker 3]

No, thats what where NICEIC said it also referred to it lol

 

[Guest55]

Hi
should the cable from the busbars to the new switch gear, be the same as the feeders into the busbars?

i've elimanted the crap so to make the Q. clearer for the kids at home.

no , you size the switchfuse tails according to the load drawn from that point , not according to the upstream protective device.

to put it in another context.........

the dno main supply down your street could be , say , 95mm.
yet the service cable jointed off the mains and entering your house to the cutout is only 16mm

but if we followed your original proposition to its logical conclusion , then every branch would need to be 95mm , which clearly isnt the case.

as for reg numbers , sorry i've run out of arsed for this evening.

;-)

 

[Pete999]

Been sorted mate thanks anyway