Fan in the kitchen

[Albert]

Hi,
In an old kitchen there is a fan connected (to the light circuit), the thing is that the instructions I have are to change the one gang light switch to 2 gang where one will be for the light and one for the fan, there is a need to connect a 3P isolator for the fan instead the ceiling rose (the fan is activated by a pull cord), there in no effect on the fan from the light switch, the fan gets the 'live' from it.
Can someone explain how this connection has to be done, according to BS 7671, and if there a basic diagram to show the wiring configuration?
Thanks
Albert

 

[John.Stitch]

Which instructions are these then?

In the kitchen I am doing I have a ceiling mounted fan and a simpe one way wall switch to turn it on.
You usually only need a three pole switch for the bathroom fan.
The sparks saw this when he came on first visit prior to certifying check and said it was ok.

 

[dingbat]

If you have a timer overrun on the fan, which requires a permanent live connection, you should ideally fit a three-pole isolator so that you can isolate for maintenance without de-energising the lighting circuit.

 

[Albert]

If you have a timer overrun on the fan, which requires a permanent live connection, you should ideally fit a three-pole isolator so that you can isolate for maintenance without de-energising the lighting circuit.

I think that you got the idea, just to explain it is not a private job, i'm doing it for a contractor, and these are council flats, instructions are coming from there. The fan is one of those that fixed on the kitchen window, can be turned on by using a pull cord. and connected to a ceiling rose, there is one wire that connects to the light switch, but I think that it is used to get the live for the fan, the light switch does not turn on or off the fan.
As you said it has to be done so in the future they can connect timer overrun etc. I am putting in a new fuse box so if necessary I can pull T&E (1.5mm2) to the 3P isolator.
As this is the first time that I am doing this kind of connection I would like to understand how it should be connected, the way the wires have to be connected in the light switch (it will be changed to a 2 gang switch, one for the light one for the fan), and how it is connected to the 3p isolator.
Many thanks
Albert

 

[securespark]

Albert

What about your boss? I'm a bit worried that he hasn't set out in clear terms what you should be doing. It is a bit odd of him to leave circuit design and layout to the apprentice!

When you say the fan is operated by a pullcord is this integral to the fan unit itself, or seperate?

Are you sure the connection to the switch is a live feed?

If the switch is being changed so that one gang operates the fan, then this new wire would be the switch wire for the fan, no?

The live & neutral and earth feed would come from the same protective device as the lighting circuit from which the switch feed has been taken.

All three conductors (live feed, switched feed, neutral (& earth)) would then go to the fan via a 3 pole isolator. This ensures that the fan can be completely isolated for maintenance - switching off at the wall switch will only isolate the switched live, not the live feed.

Then then fan is connected to the outgoing terminals of the isolator. If it is not a timer fan, then the live can be connected to either the switched live or the live feed, depending upon whether you want the fan to come on with the wall switch or have an permanently live feed. If the fan has its own pullcord switch, and no timer, then you would connect the live to the permanemt live feed as the pullcord on the fan would be used to activate the unit.

But, ideally, you need to confirm a few things with your boss as to how it should be arranged. And maybe look at the fan instructions to see what wiring options there are.

 

[Albert]

Albert

What about your boss? I'm a bit worried that he hasn't set out in clear terms what you should be doing. It is a bit odd of him to leave circuit design and layout to the apprentice!
etc......

I asked several times but as you know there are very few people in this business that will be pro. enough to spend the time.
I will explain again; the fan is an existing fan, new kitchens are installed in these flats, and all the electrics are done (only kitchen) + new fuse box Immersion and boiler.
I looked today in the fan configuration; the light switch (one gang) has 3 red wires, 2 of them connected to the common, and one to L1, in the ceiling rose (of the light ) there are 2 Neutrals and one of them goes to the fan, one live (switch live?) and earth. there is a second live (red), that is not connected to the rose and goes directly to the fan, (it seems that this is the second red from the switch common).
The fan at the moment is connected via a DP switch, but this is going to be changed to a 3P isolator, (I thing for future use, if the next tenant will have a timer).
Now; I never connected a 3P isolator B 4, or a fan directly to the light switch, if I would see a clear diagram of the way that these supposed to be connected (both options) it would be very helpful, I don't see clearly what goes in each side of the isolator (i mean L1, L2, N in both sides of the isolator). I hope that it is more clear now.
Thanks, Albert
PS: After sending this message I continued to search and found a good diagram in MK's site

 

[securespark]

Well, Albert, I've drawn out on paper what you describe, and you have:

a live feed coming into the lightswitch.

one going out of the light switch to the fan.

L1 leaving the switch and arriving at the rose.

a neutral coming in at the rose and leaving for the fan.

This means you only have L + N at the fan, and no Switched Live.

If the above is correct, then you need to take a switched live from the rose position to the fan position.

Then your incoming feed goes to one side of the isolator and the fan's connections to the other - it does not matter which terminals are incoming and which are outgoing, as long as you don't mix them up. If the terminals are marked IN and OUT however, then respect these markings.