Probably a scary question from a noob...

[Sprogginz]

I would like to install a chimney cooker hood but aside from competence what are the legalities (i.e. have to be registered) with the wiring now?

My initial assumption is to run the cable through and down my cavity wall to a wall socket next to the cooker but I am also assuming that as with most things in life it is not that simple and illegal.

The next question would be about the extraction but that would depend on the outcome of the first question!

Thanks for your attention and any advice you can give me.

 

[skenk]

I'd want to have the extraction figured out first as it's usually more difficult ('round ere anyway) to core a 4" hole to the outside than it is to install new wiring to a cooker hood.

If you're competent (small c) you would already know the legalities

The extractor will need fusing down, which will normally mean a fused spur. But the circuit you are connecting to will have to be suitable so that the new work fully complies with wiring regs (BS7671:2008). As it's in a kitchen this will all need to be notified to your LABC, or you could just get a Competent (capital C!) person to do it at a fraction of the cost and hassle (if you're lucky/have recommendations!)

By Competent i mean a 'Part P registered' spark - www.competentperson.co.uk

 

[Sprogginz]

Thanks for the reply. It would seem that this project has now just died!

My competence is just limited to the basics and looking up or being told what to do and I don't know anyone else that can do it apart from calling a spark which is going to be too expensive. It's a shame as it would be something I'd enjoy but having to worry whether I've complied with the law is too much hassle yet necessary I suppose.

My extraction question was going to be whether I could join it to the bathroom one. It runs into the kitchen and up through the loft (all behind a ceiling box of course!). The kitchen does have its own extraction fan but of course it is on the opposite external wall.

Thanks again.

 

[wingcoax]

Apart from what you now know about the electrical side of your project, you would not be able to join the ducting to the bathroom duct.

 

[skenk]

Is that always the case if a kitchen is between a bathroom and the extract point? How about using an inline fan in the loft with backdraft shutters at the intake points? I remember a thread on this before but can't remember what was said.

 

[flameport]

You can fit 2 extractors to one duct, but the cost of the joining pieces, backdraught shutters and designing the ducting to ensure proper air flow usually exceeds the cost of another fan anyway.

The problem with connecting a kitchen and bathroom together is that the kitchen extractor will usually be far more powerful than the bathroom one, so that when the kitchen extractor is running, the bathroom one doesn't work properly, as the air pressure in the duct prevents the shutters on the bathroom fan from opening fully (or at all).

 

[Sprogginz]

You can fit 2 extractors to one duct, but the cost of the joining pieces, backdraught shutters and designing the ducting to ensure proper air flow usually exceeds the cost of another fan anyway.

The problem with connecting a kitchen and bathroom together is that the kitchen extractor will usually be far more powerful than the bathroom one, so that when the kitchen extractor is running, the bathroom one doesn't work properly, as the air pressure in the duct prevents the shutters on the bathroom fan from opening fully (or at all).

That's interesting and again forgive my noob thinking, are there sort of T-Junctions I can get so I can then simply put one of these backdraught shutters next to each extractor on the understanding that I will get a bathroom that smells of a kitchen if I use them at the same time (but thankfully not vice versa!)?

 

[Sprogginz]

I'm feeling a bit less clueless now regarding the electrics after reading "Installing a Cooker Hood" so could someone please tell me if joining the fused spur to the cooker socket is allowed? I haven't checked yet to see if it is already running a spur. However, the socket is behind the cooker but the switch is above a worktop, would that matter?

If it's NOT allowed then why so? I'm just curious.

Thanks again.

 

[flameport]

There are T junctions for ducting (although they are more like Y junctions).

The problem with bath and kitchen going into the same duct isn't about getting kitchen smells in the bathroom - the backdraught shutters will prevent that.
The problem occurs when the kitchen extractor is on, and the bathroom one is needed. To open the backdraught shutter, the bathroom fan has to overcome the air pressure in the duct caused by the kitchen fan, and unless the bathroom fan is particularly powerful, it won't be able to.

It may be possible to connect a fused spur to the cooker circuit, provided the cables are installed in the appropriate zones, and the cooker circuit has suitable protection.

 

[Sprogginz]

Do the backdraught shutters have to be fitted next to the fans so the suction opens the shutters?

How do you know if the extraction is working? Are there shops that sell coloured smoke!?

Sorry for the delay, the project had to be postponed. I still appreciate any advice you can give from preventing me from any major cock-ups!

Thank you.