Cooker Hood via Cooker switch...

[JIMBOB01]

Hello to all,
I have just bought a Rangemaster Hood and want to obviously give it a power supply. From what I gather from reading previous similar questions, if I use a 3amp FCU inline from the back of the cookers electric switch, all will be ok... Is this right? Anything else worth considering? I understand that the cooker will draw a lot more juice than a wee 3 amp supply, will they not interfere with each-other?
thanks, Jim

 

[ban-all-sheds]

From what I gather from reading previous similar questions, if I use a 3amp FCU inline from the back of the cookers electric switch, all will be ok... Is this right?

Provided you can get two cables into the switch terminals, and providedyou don't end up with concealed cables where they shouldn't be. If you are burying any new cables in the wall they should be RCD protected.

• http://www.voltimum.co.uk/files/gb/attachments/niu/l/attachments/c5-43.pdf
• http://web.archive.org/web/20061110111450/http://www.niceic.org.uk/downloads/concealedcables.pdf
• IEE article
• IEE Article on 17th Edition requirements for concealed cables.

Anything else worth considering?

It's notifiable if you're in England or Wales.

I understand that the cooker will draw a lot more juice than a wee 3 amp supply, will they not interfere with each-other?

No.

 

[JIMBOB01]

I'm a a bit bemused. Of course I would like to bury the cable in the walls, but from what you are saying, and the links, the cable would have to come out and into an RCD plug!

What if I were to just add cable running from the back of a conventional plug socket, run the cable out into an FCU and then onto the hood?

The fact that the cable would be buried from start to finish is attractive, otherwise it looks like a bodge surely...

 

[ban-all-sheds]

I'm a a bit bemused. Of course I would like to bury the cable in the walls, but from what you are saying, and the links, the cable would have to come out and into an RCD plug!

Or installed in earthed metal conduit, or done in a cable type which doesn't need RCD protection, or buried >50mm deep, or you could put the cooker circuit on an RCD, or you could put an RCD FCU right next to the switch.

What if I were to just add cable running from the back of a conventional plug socket, run the cable out into an FCU and then onto the hood?

You could do that, as long as the socket circuit is RCD protected and the socket is not an unfused spur itself.

The fact that the cable would be buried from start to finish is attractive, otherwise it looks like a bodge surely...

Indeed it does.

 

[JohnD]

IMO it would be preferable to take the supply from the lighting circuit

 

[ban-all-sheds]

Wouldn't an isolation switch for the hood still be advisable?

In which case, where would you put it?

 

[JohnD]

beside the fan. it will be visible but not visually intrusive

I would go for a DP S-FCU with flex outlet to the hood

 

[ban-all-sheds]

I'd go for an engraved switch or FCU somewhere logical, i.e. grouped with others, or next to the cooker one(s) etc, and all of the cabling concealed, ending up coming out of the wall behind the hood, so that you see absolutely none of it, not even a short bit from flex outlet to hood.

 

[JIMBOB01]

I have put together what I would like to do in picture format to make it clear, is this going to be ok? Please comment...
I intend to just run cable from the back of the current double plug socket into the FCU and onto the hood. Are there any problems you can foresee....
I assume the earth from the double plug runs straight to the earth terminal on the metal conduct for the FCU, as does the earth for the hood.
View media item 18952Jim

 

[ban-all-sheds]

Metal conduct?

Do you mean conduit?

Where will you be using this, and why?

Wherever it is, it should be earthed, not used as the earth path.

How thick is the wall - will you be able to have a horizontal chase more than 50mm deep (the back of it will have to be, if you want the cable to be deep enough) without weakening the structure?

 

[JIMBOB01]

Conduit of course, sorry.

The coduit is to mount the FCU in the wall, am I right or does it not need to be metal, will a plastic one do?

The wall is an outside double skinned wall so i intended to drill multiple holes where the vent is going outside, knocking through the brickwork and via the cavity fish the cable from the back of the FCU up to where the hole is for the vent. This would be at least 50mm deep. Or should I just channel the wall, it makes no difference to me, whatever is best and proper.

I'm not entirely clear what you mean by 'not used as the earth path'. The whole system is earthed via trip switch box is it not? If I use a plastic conduit instead of a metal one the earth will be as it was I assume via the system already in place. Whatever happens I do not want to make anything live!!
View media item 18953

 

[JIMBOB01]

Sorry, when I have said conduit, I mean mounting boxes, the conduit is what the cable runs inside isn't it !!

Duh !

 

[JIMBOB01]

View media item 18954

 

[JohnD]

your method is a bit unusual

It is normal to use a galvanised metal box for accessories mounted in the wall.

It is very abnormal to try to chase 50mm into an ordinary house wall, you are half way through the bricks or blocks and may have a crack going beyond the chase, so that it loses structural integrity. Less than an 18mm chase is enough to get an oval plastic conduit in and replaster neatly. Often you can do it in the depth of the plaster. If a metal plasterer's trowel (which can nick cable) is not being used you can even plaster the cable in without capping or conduit.

I presume you are thinking of a deep chase to save having to RCD protect the circuit. It would be better to RCD it. Depending on the type of Consumer Unit you have there may be different ways this could be done.

Without wishing to be unkind, I fear you are not yet equipped with the skill and understanding to do this job safely. Posts on a website are not the way to learn. As already mentioned, electric work in kitchens is notifiable, I am sure you would do better to engage an electrician who is a member of a Competent Persons scheme and will do the design, installation, testing amd paperwork to the correct standard.

 

[ban-all-sheds]

You shouldn't run cables in a cavity.

Horizontal chases can easily weaken walls, and should not be more than ¹/6 the thickness of the wall or leaf, which you'd know if you had the necessary guides to the wiring and building regs.

Your description read as if you planned to take the cpc to the conduit at one end and then from the conduit at the other end for the appliance, rather than just running it through the conduit.

Basically you seem to be confused by techniques, rules, terminology etc, and are groping your way towards doing something on the basis of asking the random questions which happen to occur to you. This is fraught with danger, as you could easily fail to ask about something you don't know because you have no idea that it even exists and that you don't know it.

Please take some time out and do some proper studying of wiring systems, installation techniques, the theory & practice of circuit design and construction, the rules and regulations etc.

Get books such as the ones recommended here, and acquire a sound basis of knowledge and skill before attempting electrical work, rather than making it up as you go along.

[EDIT]Doh![/EDIT]