Cooker hood and bathroom fan connection via duel appliance outlet plate.

Tonykakz · May 8, 2021

I wish to install a bathroom extractot and cooker hood from an existing 32 amp 6mm cable . I intend to use a duel applliance outlet plate to split into two 6mm cables running to seperate 3amp FCU's from there 1mm cables to all parts that follow . See diagram . Is this in line withs regs. Thanks .

Tonykakz · May 9, 2021

polaroid said:
FYI with regards to placing FCU beyond the point of cable reduction:

434.2.1 Except where Regulation 434.2.2 or 434.3 applies, a device for protection against fault current may
be installed other than as specified in Regulation 434.2, under the following conditions:
In the part of the conductor between the point of reduction of cross-sectional area or other change and the position
of the protective device there shall be no branch circuits or socket-outlets and that part of the conductor shall:
(i) not exceed 3 m in length, and
(ii) be installed in such a manner as to reduce the risk of fault to a minimum, and
NOTE: This condition may be obtained, for example, by reinforcing the protection of the wiring against external
influences.
(iii) be installed in such a manner as to reduce to a minimum the risk of fire or danger to persons.

Length and.... protection from damage need to be considered as damage to the cable after the CSA reduction but before the fuse, the fault current will over load the cable before the main protective device trips?

Open to correction

I thank you for your advice. I will take this into account. I think i will not reduce the cable size to the FCU's just to be on the safe side. Yes that was my concern about reducing the cable size before the FCU's, yes the real danger of overloading the reduced cable size before the fuse blows. Thanks.

polaroid · May 9, 2021

Tonykakz said:
I thank you for your advice. I will take this into account. I think i will not reduce the cable size to the FCU's just to be on the safe side. Yes that was my concern about reducing the cable size before the FCU's, yes the real danger of overloading the reduced cable size before the fuse blows. Thanks.

I just thought I would state the regulation for information purposes but Dartlec does make some very good points in relation to my post so please consider those.

With RCD protection and if the cables routes are chosen carefully i don't think it would be much of an issue.

Tonykakz · May 9, 2021

Dartlec said:
That's correct for any given situation I'd agree

in this case, we have a 32A OPCD and 2.5mm feeds to the FCUs, which is equivalent to a spur on a Ring Final Circuit, which as we know is acceptable (with no 3m limit that I'm aware of either...)

In any other combination of cables/OPCD, you could use the adiabatic and other calculations to determine whether the cable could deal with fault protection along it's length...

In this case, with a quick calc and some assumptions, the cpc requirement is less than 1.5mm for most cases.

The fact that an RCD is installed also should ensure rapid disconnection for any cable damage.

Provided the cables are run in safe zones, with suitable installation practices, I don't think there is anything 'wrong' with this setup, though it is not necessarily the one I would choose.

There is the caveat about Part P notification for the bathroom fan, and that correct installation does require testing that the earth is correctly terminated at each point of the chain.

polaroid said:
I just thought I would state the regulation for information purposes but Dartlec does make some very good points in relation to my post so please consider those.

With RCD protection and if the cables routes are chosen carefully i don't think it would be much of an issue.

So let me recap! From consumer unit 32amp circuit RCD protected . 6mm Cable of around 7 to 8 feet long runs to airring cupboard. Here is where the new work begiins . This was.an old shower cable . So i want to split the cable two way using a duel.plate . From the duel plate run two 6mm or 2.5 mm cables to 2 FCU's cables to FCU's no more than 4 inches long. Then for the Bathroom fan a cable of 4 inches into fan isolator. Then a cable of 14 inches into junction box and then a cable of 6 feet to bathroom extractor . All cable size from FCU will be 1mm. For the cooker hood from the FCU run a cable of 3 feet to flex outlet plate and connect to cooker hood. So the only real issue hereis if it is permitted to reduce the cable size of 6mm from consumer unit running to Duel plate to 2.5 from duel plate to FCU's of stick with the 6mm run right through to FCU's.