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Cabling out of back of consumer unit

lyledunn

This consumer unit is installed directly on to an internal stud wall. Note the cables coming through the rear. Makes a neat job. However, following a fire in a consumer unit in a relatively new house quite a number of years ago, I have always advised that when making cable entry via the rear, holes should be as tight as possible and/or intumescent sealing arrangement applied. In the case of that incident, the fire didn’t spread but smoke entered the stud and made its way out through an aerial socket in a bedroom of the floor immediately above the consumer unit, which was located in the ground floor cloak room. Volumes of choking smoke entered the bedroom where a baby was sleeping. It was quite some time before the smoke detector in the landing operated to wake the parents, narrowly missing a tragedy. 
The photo shows very common wiring practice which is likely present in many domestic situations. 

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    I would tend to agree. 

    It would be great if the manufacturers came up with reasonably priced intumescent sealant solutions that still enabled reasonably easy installation of extra circuits.

    Personally I use fuse box CUs and they have plastic inserts that reduce the size of the rear holes. I think they have passed the glow wire test, not sure if this is good enough.

    Occasionally I use intumescent spray foam, but very reluctantly as it's going to make any additions challenging for the next guy. Especially reluctant with cables running inside walls as gaining access to make a hole for a new cable without putting a hole in the wall is going to be difficult.

    There is the option of cutting 20 or 25mm holes in the back lower down and using intumescent glands. But only good for rewires as in most cases existing installs don't have enough slack cable to enable this solution.

    I would think an intumescent gasket stuck to the back of the board would expand enough to block standard cable holes. And if supplied as standard with CUs would not cost that much.

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  • 0

    I would tend to agree. 

    It would be great if the manufacturers came up with reasonably priced intumescent sealant solutions that still enabled reasonably easy installation of extra circuits.

    Personally I use fuse box CUs and they have plastic inserts that reduce the size of the rear holes. I think they have passed the glow wire test, not sure if this is good enough.

    Occasionally I use intumescent spray foam, but very reluctantly as it's going to make any additions challenging for the next guy. Especially reluctant with cables running inside walls as gaining access to make a hole for a new cable without putting a hole in the wall is going to be difficult.

    There is the option of cutting 20 or 25mm holes in the back lower down and using intumescent glands. But only good for rewires as in most cases existing installs don't have enough slack cable to enable this solution.

    I would think an intumescent gasket stuck to the back of the board would expand enough to block standard cable holes. And if supplied as standard with CUs would not cost that much.

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