Mini-trunking and non-inflammable CUs - how is it supposed to work?

[Chris Green]

I sort of understand how cables going into round holes in a CU can have the gaps filled so that the non-inflammability requirement is fulfilled. ...or in the case of round cables they will fit snugly in the right sized gland.

However I really can't see how one is meant to use the relatively large rectangular 'mini trunking' holes while retaining fire protection. The holes in my new CU are something like 5cm x 3cm, is one meant to run cables in trunking that size up to the holes with the trunking butted up against the CU case? Or is the trunking meant to run along the CU with holes in the trunking to route cables into the CU?

Either way, where does the trunking stop? Does one have to gunge up the other end where the cables come out of the trunking with intumescent gunge? Since my CU is flush mounting the trunking isn't going anywhere in particular and there's not another end where the cables disappear into a wall or something.

[Alan]

You've forgotten the big hole at the front where the CB/switch sits. 30cm by 6cm. The only part that has to be non-flammable is the casing. It is a big con by the Manufacturers who were meant to supply non- flammable plastic cases years ago, and they certified them as non- flammable, yet when tested they did burn. Along with poor installation where cables were left loose, or not tight enough in terminals,this caused a number of fires so 'something had to be done'. AFAIK, no action has been against the Makers who supplied these non- certified CU's. Is it fraud? I'd say so.

[newshound]

Mini-trunking is PVC which is somewhat fire resistant.