Re-connecting Extractor fan

corner · 2 Mar 2004

I would like to reconnect a bathroom fan which was removed before I bought the house.(wire buried in Wall and covred over)I've uncovered the cable and have fitted the fan in postion.
I would like to change the existing single gang switch to a two gang so that I can operate the light and fan separately.
On removing the switch faceplate I discover 4 incoming twin and earth cables.
Backplate is earthed, all 4 black wires are bound together and 3 of the 4 red are connected to the existing switch. the 4th red is not connected at all.
Copying the existing format I have added the 2 gang switch but not connected the 4th red. Light continues to work as before
How do I now get this to operate my fan ?

ban-all-sheds · 2 Mar 2004

Which switch terminals do the reds go to?

Which one(s) are permanently live?

What is at the other ends of the T/E cables?

Do you have any reason to believe that the 4th one goes to the fan?

Does the fan just need a switched live, or is it a timer-overrun one that requires a permanent live as well?

How much investigation have you done? That's not meant to sound sarky BTW - it's just that unless your wiring was done by Mobius Electrics Ltd, each of your cables will have at least two ends, and it's important to know what is at each of them...

PS - when you say "all 4 black wires are bound together " I hope you don't mean twisted together and taped up....

corner · 2 Mar 2004

L1,L2 and common
Yes all the blacks are taped together - I checked 3 other light switches in the house and all appear to be the same convention - ie switch is connected entirely with red wires and all blacks are taped together with insulating tape and unconnected in the back of the fitting.
The fan is not a timer overun style
Not a great deal of investigation as yet.

ban-all-sheds · 3 Mar 2004

corner said:
L1,L2 and common

Have you got 2-way switching for this light?

Yes all the blacks are taped together - I checked 3 other light switches in the house and all appear to be the same convention - ie switch is connected entirely with red wires and all blacks are taped together with insulating tape and unconnected in the back of the fitting.

They shouldn't be there. What happens to the black cores at the other ends? Do you have a meter? - Is there a voltage between the red&black?
Two thoughts occur immediately
1) The idiot who wired this took neutrals to the switches, thinking he had to do that.
2) The idiot who wired this wanted red cores for his switched lives and did it by using 2 more T/E cables, ignoring the black cores. Alhough if that's the case, why not cut them off?

Either way, it's not right - you need to find out what's at the other ends.

The fan is not a timer overun style
Not a great deal of investigation as yet.

Found any other oddities?

corner · 3 Mar 2004

The light switching is not 2 way
and as far as I know the T/E cables only feed the ceiling lights - I'll get into the loft space and check further

ban-all-sheds · 3 Mar 2004

corner said:
The light switching is not 2 way

If it's not two way, and you don't have the bizarre situation of the switch turning one light on and one off, and vice versa, as you operate it, then you might have an unused or disconnected live wire somewhere - it depends on which is the live feed to the switch. If you don't have a meter to test which is which I suggest you get one - by the sounds of it you are not going to be able to rely on any common sense or conventionality with the wiring done by Mr Idiot.

and as far as I know the T/E cables only feed the ceiling lights - I'll get into the loft space and check further

Take care...

corner · 3 Mar 2004

I'll get a meter and check

Assuming that the 4th - currently unconnected - red wire turns out to be to the fan, can I take the supply from the light switch to feed the switching of the fan.

In some of the other switches in the house they seem to have looped across from 1 gang of switch to the other.

ban-all-sheds · 3 Mar 2004

corner said:
I'll get a meter and check

Assuming that the 4th - currently unconnected - red wire turns out to be to the fan, can I take the supply from the light switch to feed the switching of the fan.

Yes

In some of the other switches in the house they seem to have looped across from 1 gang of switch to the other.

It's quite common to do this with the live feed to the switch.

corner · 4 Mar 2004

OK - Have now established permanent live on L1 with a meter, still to get into the loft.

If I loop L1 to the other switch and connect the other red wire (from the fan ??) what about the neutral which is currently bound with the other black wires in the back of the switch box.

At the fan end of things the unit says it's double insulated and does not require earthing - consequently I have nipped off the earth wire at the fan.

ban-all-sheds · 8 Mar 2004

corner said:
OK - Have now established permanent live on L1 with a meter, still to get into the loft.

If I loop L1 to the other switch and connect the other red wire (from the fan ??) what about the neutral which is currently bound with the other black wires in the back of the switch box.

Are you sure that they are actually neutral wires, and not just unused ones that are there because Mr Idiot decided that he would not take the live feed to the switch with one conductor in some T/E and take the switched live away with the other conductor? Neutrals are not taken to light switches, and have no place there.

If they are neutrals then I would suggest regularising the connection of neutrals at the ceiling roses/JBs, using the black conductors to carry the switched lives (not forgetting to mark them with red tape or sleeving), and completely removing any lengths of T/E that are now superfluous.

At the fan end of things the unit says it's double insulated and does not require earthing - consequently I have nipped off the earth wire at the fan.

Well then, let's hope that you, or a future occupant never wants to fit a fan that is not double insulated!

corner · 8 Mar 2004

I think that I now have some success, well everything works anway, although I take it you would not have nipped off the earth at the fan end ? - Is it worth stripping back more T/E and exposing the earth?

The 4 T/E cables are 1 x incoming (from another switch further down the chain), 3 x outgoing, fan, Shaver socket(earthed) and ceiling lights.

All black/Neutrals are connected in a connector block and taped up as mentioned before

ban-all-sheds · 8 Mar 2004

corner said:
I think that I now have some success, well everything works anway, although I take it you would not have nipped off the earth at the fan end ? - Is it worth stripping back more T/E and exposing the earth?

No point now - you don't at the moment need the earth. If there's enough spare cable for you to do this then it can be done in the future if and when it's needed

The 4 T/E cables are 1 x incoming (from another switch further down the chain), 3 x outgoing, fan, Shaver socket(earthed) and ceiling lights.

All black/Neutrals are connected in a connector block and taped up as mentioned before

A light switch needs 1 incoming conductor (live) not two.

Devices controlled by the switch have 1 conductor coming from the switch (their live feed), not two.

The neutrals for the lights and anything else that is on the lighting circuit (shaver socket, fans etc) stay up in the lighting circuit, going from one light to the next, or going direct to the shaver socket, fan isolation switch etc, they should not run to and from the switch.

wiring%20lights%20schematic%20diagram%202.gif

I would advise that you remove all of these neutrals running backwards and forwards to choc-block connectors (or, dangerously, a twisted taped up mess) behind the switches and wire it up with the conventional, accepted topography.

corner · 8 Mar 2004

Thanks,

I see that I have a big job in hand - all of the switches that I've uncovered in the house are wired in this way, very congested, particularly the 3 gang switches.

The house is maybe 7-8 years old - is the way it's wired dangerous ? or just unconventional ?should I take it say to NHBC?

ban-all-sheds · 8 Mar 2004

corner said:
Thanks,

I see that I have a big job in hand - all of the switches that I've uncovered in the house are wired in this way, very congested, particularly the 3 gang switches.

The house is maybe 7-8 years old - is the way it's wired dangerous ? or just unconventional ?should I take it say to NHBC?

If the black wires are actually part of the circuit, and not just sitting there, i.e. they are carrying current and they are just twisted together, then this is dangerous, as the contact might not be good enough, and it might overheat. Also, as you say, it's very congested in some of the boxes, so there is a risk of damage to the wires.

If this is how the house was wired up when it was built, and it is still under guarantee then I would say that you have a case for going to the NHBC, but I'm not a lawyer. It might be worth having a full inspection done, but whether you could get the cost of that back from the NHBC, or the builder, I have no idea - a trip to a solicitor or CAB might be in order.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Re-connecting Extractor fan

Similar threads