Split main

[T spark]

Question I have been called out to a job that has a number of 3 phase boards supplied by neutral blocks so there is no main switch to isolate all the boards does anybody know the regulation number to which this contravenes please any help would be great thanks

 

[Deleted member 26818]

It depends, whether the 3phase boards are part of a single installation, or are part of separate installations.
The Regulation that has requirements for a single main switch is 537.1.4.

 

[T spark]

Yes they are all part of 1 installation 1 3phase d/b 1 single phase board 1 3phase switch for oven all fed from henly blocks from meter

 

[Deleted member 26818]

Then in order to comply with the Regulations, there should be a single point of isolation, or a warning notice, indicating that there are multiple points of isolation and detailing where the points are.

 

[malcolmsanford]

If you look up the definition of Distribution board you will see the actually enclosure does not have to have an means of isolation as long as there are remote means.

 

[T spark]

Ok thanks for that I only needed the info for the company I am doing the work for has there maintenance sparks doing this practice of splitting mains with henly blocks also they take 16m tails out off the supply side of the distribution board incomer which already has 25m tails backed up by 100amp fuses which to me is really bad practice but I need to know the reg numbers that these relate to thanks again

 

[malcolmsanford]

TBH I would not consider reducing the CSA of the mains as bad practice as long as you have assessed the situation. Have a read of 433.2.2 and 434.2.1

 

[T spark]

The 16m tails are bunched with the 25m tails where they go in to the incoming switch in a terminal that is designed for one cable as they have had to cut strands off the 16m tails and I don't think 16m tails should be on 100amp fuses from the main

 

[malcolmsanford]

Often in commercial/industrial situations you will find doubling up on connections, especially on main switch gear that are lugged and then connected via nut and bolt, you even see it on bus bars as well, though I prefer to fit direct onto a bar, but sometimes you can't and you have to make best of what you can.

I do agree that on a compression screw terminal shaving strands off of a conductor and wedging it in to fit is not good practice and is prone to heat damage.

 

[T spark]

I feel the same I too have split mains in a switch fuse with crimped lugs and nuts and bolts but on this installation where this has happend and the main is already split with henly blocks in an emergency the girls in the shop would not know witch switch to switch off ther should be a main switch in-between the meter and henly blocks to isolate the whole installation as it is now you would switch off the biggest D/B thinking the others were sud boards feed from D/B 1 yet half the installation will still be live