Re: Cooker hood wiring

[Dave Plowman]

What are the options available to me to wire up a cooker hood, I can think

> of three ways but whether these are allowed/legal I do not know: > 1. Wire it into the lighting circuit, but then there is no accessible > isolating switch.

Neither is there for most lights. It presumably has its own on off switch?

2. Wire it into an FCU hidden behind the hood, but then do I also need an > accessible isolating switch?

Is it possible to wire it such that the cable comes out of the wall into it - ie behind it? If the cable comes out the top say near the back it's often the tidiest way to use an FCU or at least cord outlet even when wired off the lighting circuit.

3. Wire it into the big red cooker switch.

Not a good idea, IMHO.

I don't really want any visible wiring or socket/FCU. I favour number 2, > but I don't fancy adding a separate isolating switch as well.

Can't see why you'd need one.

Anybody help with this?

[Andrew Gabriel]

...but you need a means of isolating appliances containing motors.

You could use an FCU or an unfused double pole switch, or a bathroom fan isolating switch (ignoring the 3rd pole, but it will have an appropriate legend on it). Some cooker hoods have quite high power fans nowadays, so check the loading on your lighting circuit first.

You need to be able to operate it for maintenance of the cooker hood, i.e. before you open or take the hood down. It doesn't need to be accessible for normal day-to-day use. If it's far enough away (or out of sight) of the cooker hood such that someone working on the hood could not be said to be in direct control of it, it needs to be a type of switch which can be locked off. Bathroom fan isolating switches are often of this type, although they don't come with the lock (it engages in two tiny holes either side of the rocker, which you probably haven't noticed unless you looked for them, holding it in the off position).

BTW, and plug and socket is also acceptable means of isolation.

My cooker circuit has been turned into a switched radial circuit by fitting 3 socket outlets in place of the original hardwired cooker outlet. One has the oven plugged in, another has the gas hob ignition plugged in and the third was for some appliance previous occupant must have had in the cupboard under the oven. If your oven plugs into a 13A socket and you don't have electric hob, I see nothing wrong in doing this.

[Christian McArdle]

Provided the MCB/fuse is of a sensible rating, of course. (i.e. a 32A or 20A B curve). This will usually be the case, although frequently cooker circuits are wired with higher ratings, such as 40A or 45A, which would need swapping out. Also, you'll need to prove that the sockets aren't likely to be used for outdoor portable equipment, as they would need an RCD/RCBO.

Christian.

[Andrew Gabriel]

It is in this case, and 6mm² cable.

Well, there aren't any RCD's in this house at the moment. If I get round to it before Part P comes into force, I will fit a nice new CU with separate RCD protection on each ring, and take the immersion heater off the ring circuit. If I don't get round to it in time, it will stay with no RCD protection and with the immersion heater on the ring circuit forever more, or until it causes a fire and burns the house down...

[John Greenwood]

Hi Andrew,

Thanks for your reply. I have decided to do the following:

Install a 13A socket behind the cooker hood which will be completely hidden. The cooker hood will be plugged into this. The socket will be connected to a visible FCU at worktop level. The FCU being on the kitchen ring circuit.

Does this sound as if it is in line with the regulations?

Thanks,

John

[Andrew Gabriel]

Yes, but you don't need the FCU. If the plug can't be withdrawn without first dismantling or removing the extractor fan, then a double pole 20A switch will do (unfused as there is a fuse in the 13A plug). If you can get to the plug for such maintenance, then you don't even need the switch. You don't need to be able to get to the plug or switch easily for everyday use -- they are isolating switches for maintenance, and not required for functional switching (hood presumably has its own switches built-in for that).

[John Greenwood]

Thanks Andrew, all a lot clearer now.

[Andrew McKay]

I think I might be a little concerned about the environment that would exist behind the cooker hood. By virtue of the fact it is a cooker hood one expects the general area to get a bit warm, and maybe laced with condensation/steam and other environmentally unfriendly options.

That probably doesn't make it a problem for the regs as such, but page

2 of Electrical Commonsense #101 might apply.

The other issue I would raise in this situation is that if you needed to take the power off that cooker hood fast, do you intend that the cooker hood has to be stripped before the mains to it can be disconnected? If so, that doesn't sound like an ideal situation. It'll be a right royal pain in the butt if the fuse to the cooker hood blows and you've got to take the whole thing apart to check it out!

Andrew

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[BigWallop]

You won't need any FCU in the circuit if you're making the socket in as part of the ring main. If you're making the socket for the cooker hood a spur off from the ring main in the kitchen, then a fused spur unit can be placed beside the socket where you're taking the spur from. Then you take a single cable up to the socket behind the cooker hood.

As long as the cooker hood can be completely isolated from the electric's, both live and neutral, for maintenance reasons, then that is all that is needed. This is why Andrew recommended either a double pole switch which breaks both live and neutral supply, or a switched fused spur if you were removing the plug.

A switched fused spur with flex outlet would be the neatest way, as this means you're only taking one cable from the existing ring circuit, and connecting the flex in to the switched fused spur, which is quite within the regulations.

[Andrew Gabriel]

Yes, switching the spur (and not breaking the ring;-) You have to have a fuse somewhere, be it in a FCU or in the appliance plugtop, but you don't need more than one, and it doesn't have to be at the beginning of the spur.

[Andrew McKay]

Maybe a couple of ideas:

1) Take the cable thru one of the cupboards at the side of the cooker hood, and have the socket in there (you do have a side cupboard to the cooker hood?). 2) Channel down to beneath the work surface, and put the connection in a cupboard under there. 3) Take the connection up and to the side, wired into a fused spur.

Andrew

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[Fishter]

Stupid question alert....

What's an FCU? (Acronyms escape me sometimes....)

[Christian McArdle]

Fused Connection Unit.

And if that hasn't jogged your memory, it is a device the size of a single socket outlet that combines some or all of the following features.

1. A switch (optional)
2. An indicator light (optional)
3. A fuse (compulsory)
4. A flex outlet on the front (optional).

Christian.