Hi. I have found myself slightly confused as to how to replace a light in my house and was hoping someone may be able to offer some advice. I have already removed the previous light, but was unable to check how it was wired (would you believe that the previous owner had plastered the wiring into the rose!).
What I have now is 3 cables hanging down from the ceiling. 2 of these cables contain an insulated red wire, an insulated black wire and an uninsulated earth wire. The third cable contains only a red wire. The light is controlled by 2 switches at either end of the room. The light itself has an earth connection, a live connection and a neutral connection.
I am completely lost as to how to connect this up - any advice anyone could offer me would be fantastic.
I'm sure the expert sparks in the group will be able to help. I have a question for you, was the light switched from 2 places like a hall light that can be switched on/off from upstairs and downstairs?
On Fri, 9 Jul 2004 08:51:35 +0100, NOMAN strung together this:
Firstly, this is a most likely scenario, check that they are with a meter before connecting up and switching on.
Logically, I would say the two blacks are neutrals, the two reds are permenant lives and the single red on its own is the switch wire.
So, blacks into neutral terminal. Sleeved bare coppers into earth terminal. Two reds into a connector. And the single red into live terminal of the light fitting.
Hi Lurch. This sounds likely, but having only had experience wiring light roses with a single block, I felt a little lost.
I have a small plastic connector (not sure of the name of it - looks like a piece of 2-studded white lego) - is this the sort of thing I should use to connect the 2 reds (not the single red switch wire)? One wire in each end?
I suspect that you have a system where the light was originally controlled by a single switch and someone has "upgraded" the system with another switch. Does this seem likely?
Whatever it is it doesn't sound like the normal 2-way switching that you would use to get 2 switches controlling one light.
My guess is as follows:
The system was originally an end of loop "loop-in" light as per
formatting link
switch was added (at a later date). This normally requires
3-core and earth between the switches, as per
formatting link
the person who did the "upgrade" did not have any 3-core (or didn't know how to do it) he invented/used an alternative method... Here the incoming live is connected to the common of the first switch can be connected to either one of the two other terminals. Each of these terminals is connected by standard twin and earth to the corresponding terminals of the second switch. The common of the second switch is now the "switched live" that is taken back to the light fitting by a single red wire.
If this is what has been done you should find the following:
One switch (switch one) has 2 sets of twin-and-earth entering it, but the black wire on one of them is not connected (possibly cut off).
The other switch has 1 twin-and-earth and a single strand red wire (like the single red wire in the light fitting)
*IF* this is what you have you could get it working again by connecting the single red wire and the "incoming" black wire to each side of the bulb and using the other connectors in the light fitting to connect together the two remaining red wires. Not forgetting to also join all earth wires to the earth point. However, this means that you still have a black wire unconnected in the light fitting. This should not be connected back up to the other black wire, but I would also not be very happy about cutting it off or leaving it loose (no matter how much tape you add to it. Maybe it would be safe to insert it into one end of your "lego block" (normally called a chocolate block) tighten the screw and wrap that in insulating tape...
Personally if I found the wiring in the switches matched what I have predicted I would try wiring as above, including the chocolate block, but I would also regard this as a temporary measure (even if it worked) as I am sure it does not meet the regs. But I would probably also stand well back when I turned the power back on!! (You don't know what the wiring is REALLY like out of sight).
If in any doubt get someone experienced in these matters to give it a once over just to be safe!!
I'd like to heare why you think that this wouldn't make any difference (actual details)
Thank you for your detailed response.
By saying that this wouldn't be a "made-up" way of doing it you seem to be suggesting that it is a "standard" or "known" way of wiring 2 switches. If this is so then how do you justify claiming that it is "extremely unlikely" to be the case.
I think you need to think this through a bit more...
If this is a loop-in fitting there will be a twin-and-earth coming in. This accounts for one set of red, black and earth.
The switch (or in this case switch matrix) will need to link a permenant live to a switched live - this accounts for the remaining two reds.
We are now left with a black wire that has no meaningful purpose. You suggest the the OP connects this to neutral (because it's black I assume). Where do you think this wire goes? It's no good saying that you should connect all black wires to neutral without figuring out where they go - especially in a lighting circuit where we all know black is often used for switched live and the red tag if often omitted.
If I were to guess - and not too good an idea with electrics - I'd say there's the lighting radial circuit pair in and a pair out to the next fitting. The single red would be the switch return, with the feed to that switch being provided at the switch - usually from another in the same box, or close by.
On 11 Jul 2004 03:11:46 -0700, snipped-for-privacy@mxf.org.uk (Matt Beard) strung together this:
A one way switch is wired into the light fitting in exactrly the same way whether it's 1 way, 2 way or more. The chances of anyone doing what you said is highly unlikely and more than likely to be done by a completely clueless novice if it was. Obviously you're not an electrician otherwise you wouldn't even have suggested such a bodged up, diy'ed scenario.
Yes, unfortunately I don't have the space or time to repeat all the different scenarioas and combinations that can be found in a house lighting circuit so I'm presenting the most likely scenario drawn from my years of experience of all sorts of lighting wiring systems. Basically, the live feed is presented at the switch and a single is taken from the switch to the light fitting. The twin and earths are there for the neutral and earth in the fittings, the permanenrt live is most probably looped through in order to feed a outside light for instance. You'll probably find it's a totally random wiring system throughout and each fitting will be a bit different in the way that it's wired. You obviously drew your conclusions from some random thought process.
I admit that I do not make my living as an electrician, but I do have a degree in electrical engineering and am a member of the IEE.
My reasoning was as follows:
There are two basic ways to get a 2-way switching to work with a loop-in circuit: Live goes to "switch 1" which is connected to "switch
2" by 3-core and earth. The switched live comes back to the fitting from switch 1. The normal way to do this is with the live on the red-wire of twin-and-earth and the switched-live on the black wire (hopefully with a red tag).
The second option is to take live to switch 1, connect this using twin-and-earth to switch 2 and take the switched live from switch 2 to the light fitting.
Although there are other ways that it is possible to wire 2 switches from a loop-in circuit I would argue that the above are only "sensible" ones.
The fact that the OP's system has a red "single" arriving strongly suggests the second option is used (otherwise I would expect the twin-and-earth to be enough). If this is the case another simple deduction can be made - switch 1 and switch 2 could both be wired with singles, but as they are not it is reasonable to assume that they were not both wired at the same time (which is why I suggested the system had been "upgraded"). When the second switch was installed the black wire that originally carried the switched live would become redundant, but it was left as it would be too much trouble to replace the twin-and-earth with a single.
Sure, there are other options. For one thing the circuit may not be loop-in, but if this is the case it begs the question of what the other wires are doing. Your suggested wiring would be a possible solution for this, however it seems strange to have a circuit where there is permanent-live at the light fitting, and a wire from the light fitting to the switch (the switched-live), yet the permanent-live at the light fitting is from somewhere else. Being strange does not mean it isn't true though!!
I know that many houses are full of bodged wiring - some of it quite dangerous. However, the fact that I am suggesting that someone else has bodged the wiring does not make me a bodger!!!
On 12 Jul 2004 03:04:14 -0700, snipped-for-privacy@mxf.org.uk (Matt Beard) strung together this:
Hmmm! That explains a lot.
Fair enough, I'm bored with argueing now. Anyway, the reason I presented this scenario is that its exactly how my house has been wired. I've not really seen a scenario that you presented, but I've seen plenty of houses wired like mine, so there! The End.
I just wish when someone makes a comment based on what they believe to be reasonable assumptions other members of this group would respond with respect and if they disagree say so politely.
Maybe I missed a section in the FAQ saying "You are not permitted to comment unless you are a professional with X years recent experience in the exact field of the post".
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