I am running 50mm X 50mm plastic trunking round the perimeter of garage at ceiling level and planning to drop conduit down to switches and sockets. How do I feed cables from the CU into the trunking and retain the fireproof integrity of the CU? Do I need to use glands or are there alternatives. I was thinking of using galvanised couplers and brass male bushes to attach to the CU and trunking and then filling the space with intumescent sealer once the cables are in situ. I will be using anti droop clips in the trunking.

https://www.screwfix.com/p/d-line-sa...ck-of-12/2286j

How far apart do they need to be and do I only need to use them just above doorways or the full extent of the trunking?

Richard