Maxi trunking running around consumer unit

[tomodo]

Hi all, recently seen a wylex consumer unit install video, they use bush and couplings to connect to the pvc trunking running horizontal on the top on the consumer unit, is this necessary? They also show another option using strain relief grommets (inside the trunking going into the CU) How would you go about joining it to a hager unit where they have the square knockouts and also not possible for strain relief grommets either. Ive always believed it was sufficent to run the trunking butted up next to it.

Thanks

 

[cliffed]

It’s a good idea especially if the cables enter @ the Top of CU.
TBH I’ve just butted up to the Unit, if I using metal I use bush & locknuts.
Enter from the back it eliminates everything

 

[Simon47]

However it's done, you need to have a guarantee of no sharp/unprotected edges that can damage the insulation.
Personally, I'm not that impressed with bushings - wherever I've seen it done that way, it's ended up "a bit tight" because they've under estimated the bushes needed for the number of circuits.
What I've done, shamelessly copied from others, is to bolt trunking and box together - with a spacer in between made of something easy to smooth off the edges (last I used was offcut of kitchen backer board, around 1/4" thick MDF). Cut a large hole in trunking and box, slightly smaller in the spacer - so the metal edges are away from the cables.

Alternatively, leave a slight gap so you can put protective strip on the hole edges.