Light switch help

[Mystic255]

Hi all,

I’m looking for some help with some light switch wiring at my parents. Dad replaced a switch and can’t get it working correctly.

Setup is as follows.

3 gang switch in the downstairs hallway. Single gang switch on the landing upstairs.

The hallway switch controls an outside light, the hallway light and the landing light.

The problem is the landing light isn’t working as expected. The landing light must be in the on position for the hall switch to work.

E.g with the landing switch set to on, the switch in the hall turns the landing light on and off.

Parents go to bed and turn off the landing switch. The landing light goes off as expected but the switch in the hall no longer controls the landing light at all.

I’ve attached a pic of the current wiring. He labelled these himself with some tape prior to changing the switch but must have made an error as it’s not right.

Something simple I’m sure so any help much appreciated.

 

[terryplumb]

Refering to your pic ,from left to right ,which switch controls what light fitting ?
Also show us the wiring at the upstairs switch.
Do the outside light and hallway work fine ?
Has any wiring been worked on at the upstairs switch ?

 

[Mystic255]

I’ll try get a pic of the upstairs switch today. It’s a single gang.

Both switches had been working fine before the downstairs hallway switch was replaced after decorating.

Hallway switch order:
Left switch landing light.
Middle switch hallway light
Right switch outside light

Hallway and outside lights work as expected. It’s just the landing light that isn’t.

Upstairs switch want changed, though he may has swapped the wires around to test after the switch downstairs didn’t work. Can’t remember if he switched them back again.

 

[FrodoOne]

I’m looking for some help with some light switch wiring at my parents. Dad replaced a switch and can’t get it working correctly.

Which switch was replaced?
It appears that it may have been the THREE "ganged" Switches in the "downstairs hallway".

3 gang switch in the downstairs hallway. Single gang switch on the landing upstairs.

The hallway switch controls an outside light, the hallway light and the landing light.

The problem is the landing light isn’t working as expected. The landing light must be in the on position for the hall switch to work.

E.g with the landing switch set to on, the switch in the hall turns the landing light on and off.

I presume that this means that
"The "single gang" switch on the landing must be in the ON position for the Left switch of the "three gang" switch in the hallway to turn the "landing light" ON or OFF.

Parents go to bed and turn off the landing switch. The landing light goes off as expected but the switch in the hall no longer controls the landing light at all.

I’ve attached a pic of the current wiring. He labelled these himself with some tape prior to changing the switch but must have made an error as it’s not right.

You have said nothing concerning the "Correct Operation" of the other two switches in "the "three gang" switch in the hallway".

I would be quite surprised if they are now operating both the "hallway light" and "outside light" correctly!.

The Red tape on the two Brown wires from the same cable maybe the work of your Father.
However, the Red tape on the Blue wire may not be his work and maybe "original".
I suspect that those two Red taped Brown wires should go to L1 and L2 of the Left hand switch.

 

[ericmark]

What can confuse is the way each switch is divided shown with red lines here, left seems two way, in that there are three wires, but centre looks as was going to be two way with the link wire. In general one way line into com, two way line into L1 or L2.

The big problem with landing light is to work out supply, often homes are split upper and lower floors, and one need to be careful not to get a borrowed neutral situation. There may be two or three line in to a three gang switch, and the line outs must match. Otherwise it can result in danger where one thinks a circuit is isolated and you get a back feed through neutral or it if RCBO's fitted trip the RCBO's.

Getting it to work may not be enough.

I see one pair which don't seem to go into the same switch, but knit one pearl one is not how we work with electrics, I would think it will need a methodical approach.

So it seems 6 wires, and two way needs three, and one way needs two, so in all 7 wires required. The link gives us the 7th wire, but that seems to point to two line in wires, seems likely switch shown is the slave for the two way, or there would likely be more wires, trying to use logic to work it out.

Two way likely wires like this

and that line must only be used for the two way. The switch you are showing seems to be one on left of diagram. So seems likely the two lines have got mixed up. I will guess you have two MCB's for the lights?

So waiting for picture of top switch, and also are there two lighting MCB's?

 

[terryplumb]

The 2 brown wires from the same sheath ( which are both taped red) are both going to the middle switches com and L1 terminals Eric.

 

[ebee]

What can confuse is the way each switch is divided View attachment 354186 shown with red lines here, left seems two way, in that there are three wires, but centre looks as was going to be two way with the link wire. In general one way line into com, two way line into L1 or L2.

The big problem with landing light is to work out supply, often homes are split upper and lower floors, and one need to be careful not to get a borrowed neutral situation. There may be two or three line in to a three gang switch, and the line outs must match. Otherwise it can result in danger where one thinks a circuit is isolated and you get a back feed through neutral or it if RCBO's fitted trip the RCBO's.

Getting it to work may not be enough.

I see one pair View attachment 354189 which don't seem to go into the same switch, but knit one pearl one is not how we work with electrics, I would think it will need a methodical approach.

So it seems 6 wires, and two way needs three, and one way needs two, so in all 7 wires required. The link gives us the 7th wire, but that seems to point to two line in wires, seems likely switch shown is the slave for the two way, or there would likely be more wires, trying to use logic to work it out.

Two way likely wires like this View attachment 354190 and that line must only be used for the two way. The switch you are showing seems to be one on left of diagram. So seems likely the two lines have got mixed up. I will guess you have two MCB's for the lights?

So waiting for picture of top switch, and also are there two lighting MCB's?

Could I just point out that whilst the switching arrangement shown in your diagram is correct Eric that there is another (older traditional in my opinion) way that two way switching might be wired in switches and often is?
Com on one of the two switches is fed as L (feed) and com on the other switch is L (return) to the lamp, L1 & L2 being strappers connected by a run of T & E cable usually.
The L feed is a permanent and might be taken from a ceiling rose or from a joint box or from a switching arrangement to another switch on the same plate for example.
All these different alternatives can sometimes make lighting connections difficult to follow by the uninitiated.
If different protocols are followed in the same installation it can cause a bit of scratch head situation too.

 

[Mystic255]

Which switch was replaced?
It appears that it may have been the THREE "ganged" Switches in the "downstairs hallway".

Yes the 3 gang in the hallway was replaced.

I presume that this means that
"The "single gang" switch on the landing must be in the ON position for the Left switch of the "three gang" switch in the hallway to turn the "landing light" ON or OFF.

This is also correct.

I would be quite surprised if they are now operating both the "hallway light" and "outside light" correctly!.

Those are both working as expected

 

[Mystic255]

What can confuse is the way each switch is divided View attachment 354186 shown with red lines here, left seems two way, in that there are three wires, but centre looks as was going to be two way with the link wire. In general one way line into com, two way line into L1 or L2.

The big problem with landing light is to work out supply, often homes are split upper and lower floors, and one need to be careful not to get a borrowed neutral situation. There may be two or three line in to a three gang switch, and the line outs must match. Otherwise it can result in danger where one thinks a circuit is isolated and you get a back feed through neutral or it if RCBO's fitted trip the RCBO's.

Getting it to work may not be enough.

I see one pair View attachment 354189 which don't seem to go into the same switch, but knit one pearl one is not how we work with electrics, I would think it will need a methodical approach.

So it seems 6 wires, and two way needs three, and one way needs two, so in all 7 wires required. The link gives us the 7th wire, but that seems to point to two line in wires, seems likely switch shown is the slave for the two way, or there would likely be more wires, trying to use logic to work it out.

Two way likely wires like this View attachment 354190 and that line must only be used for the two way. The switch you are showing seems to be one on left of diagram. So seems likely the two lines have got mixed up. I will guess you have two MCB's for the lights?

So waiting for picture of top switch, and also are there two lighting MCB's?

Thanks for the detailed response.

Here's the pic of the upstairs landing switch.

There are 2 MCB's 1 for upstairs lights and 1 for downstairs lights, he switches both off when making any changes as a precaution.

 

[ericmark]

Yes we were taught this at school,

however in real life this means a connector block in the switch, where the

method shown here the switch terminals are enough, there is also

joint in the ceiling rose method, which would upset the wire count when working out what has been done. However now we have picture of top switch, seems first diagram was correct, centre switch 1 way L1 seems to be one line feed in, either left L1 or L2 should be other line feed in, but I would be getting my meter out to test.

One of these

is the line feed for the two way, I would either turn off the feed if on a MCB for upper floor or put in a choc block safe, then get down stairs sorted two switches to right, then reconnect the two way switching, to insure lines are not mixed up.

 

[ebee]

No you don`t always need a connector block with that one, dependant on exactly how you run it though.
In fact "that new fangled method of running 3 core and E from one switch to the other" needs a connector block in it (as I heard about one person exclaiming.
Apparently he was conversant with the T & E strappers between switches and a single (or single and earth) at each end common.
So far so good but his understanding of then doing a conversion for one way switching (T & E feed and return from existing one way position) then a mod to two way switching only needs a 3c & E from existing switch to the other.
But, rather than changing the existing T&E switchwire from Com & L1 to L1 & L2 instead then 3 core and E to the three terminals of each switch. He kept the com as say the feed on one switch and the return into a connector block and that connected the third core of the 3c & E to the com of the new switch and the remaining two cores were the strappers.
Obviously both systems worked ok but he always needed a connector block for each of his conversions.
The problem is that lighting wiring can sometimes fog the unwary with differing variations and then mixed variations too.

 

[Mystic255]

The problem is that lighting wiring can sometimes fog the unwary with differing variations and then mixed variations too.

I'm certainly confused now at this point!

However now we have picture of top switch, seems first diagram was correct, centre switch 1 way L1 seems to be one line feed in, either left L1 or L2 should be other line feed in, but I would be getting my meter out to test.

One of these

is the line feed for the two way, I would either turn off the feed if on a MCB for upper floor or put in a choc block safe, then get down stairs sorted two switches to right, then reconnect the two way switching, to insure lines are not mixed up.

I have a multimeter, would that be quicker to help test? I'm not sure how to test this scenario, but I'd like to learn if you can point me in the right direction.

 

[ericmark]

I would normally use some connector block

so with power off I can put the wires in it temporary while I test. I would likely start with a bit of guess work, I think likely one of three are line in, so put them in the connector block then test to see which it is, what you are looking at is a truth table. So you label the wires 1 to 6 and slowly you progress, first which one is line down stairs, then line upstairs, I often use the earth as reference (return for meter lead).

So you should get something like:-
1
2 Line up
3
4
5 Line down
6
So you connect line down to 1,3,4,6 in turn, and you find say 3 is hall and 6 outside.
Now you only have 1 and 4 left, so they will go with Line up for two way, line up into L1 so trial and error is 1 or 4 L2 or Com.

It is simple common sense, just step by step.

 

[FrodoOne]

The two-way switching is wired as in the third diagram of ericmark in Post#10,
except that
the Line is connected to the switch on the landing and
the Lamp is connected to the Left switch in the hallway.
with the Line being available at the Left switch - for other uses.

Since the Hallway light and the Outside light are both switching correctly,
the Line wire supplied from the landing must be the Red-tape identified wire now connected to L1 of the Centre switch in the hallway.

(The Common connections of the two two-way switches are connected by the single Brown (White sheathed) wire labeled as L at the hallway switch.)

The wire to the landing Light must be the Brown wire labeled A in L2 of the Left switch.

The Red-taped Brown wire now in L1 of the Left switch should be moved and joined with A in L2 of the Left switch
and
a new Link wire installed between L1 of the Left switch and L1 of the Centre switch.
-------------------------------------------------------------------------------------------
While the above should "work",
the wiring/connections would be more "logical" if all of the following were done, instead!

The Red-taped Brown wire now in L1 of the Left switch should be moved and joined with A in L2 of the Left switch (as above).
The Red-taped Brown wire (in coming Line) in L1 of the Centre switch should be moved to L1 of the Left switch.

The "Link" from Common of the Right switch to L1 of the Centre switch should be removed
and
the Brown Wire (Hallway Light) in the Common of the Centre switch should be moved to L1 of the Centre switch.

A new "Link" between L1 of the Left switch (in-coming Line) to the Common of the Centre switch should be installed
with
a new "Link" also installed between the Common of the Centre switch
and
the Common of the Right switch.
These latter two "Links" connect the (in-coming) Line from L1 of the Left switch to the Common terminals of the Centre and Right switches.

 

[Mystic255]

The two-way switching is wired as in the third diagram of ericmark in Post#10,
except that
the Line is connected to the switch on the landing and
the Lamp is connected to the Left switch in the hallway.
with the Line being available at the Left switch - for other uses.

Since the Hallway light and the Outside light are both switching correctly,
the Line wire supplied from the landing must be the Red-tape identified wire now connected to L1 of the Centre switch in the hallway.

(The Common connections of the two two-way switches are connected by the single Brown (White sheathed) wire labeled as L at the hallway switch.)

The wire to the landing Light must be the Brown wire labeled A in L2 of the Left switch.

The Red-taped Brown wire now in L1 of the Left switch should be moved and joined with A in L2 of the Left switch
and
a new Link wire installed between L1 of the Left switch and L1 of the Centre switch.
-------------------------------------------------------------------------------------------
While the above should "work",
the wiring/connections would be more "logical" if all of the following were done, instead!

The Red-taped Brown wire now in L1 of the Left switch should be moved and joined with A in L2 of the Left switch (as above).
The Red-taped Brown wire (in coming Line) in L1 of the Centre switch should be moved to L1 of the Left switch.

The "Link" from Common of the Right switch to L1 of the Centre switch should be removed
and
the Brown Wire (Hallway Light) in the Common of the Centre switch should be moved to L1 of the Centre switch.

A new "Link" between L1 of the Left switch (in-coming Line) to the Common of the Centre switch should be installed
with
a new "Link" also installed between the Common of the Centre switch
and
the Common of the Right switch.
These latter two "Links" connect the (in-coming) Line from L1 of the Left switch to the Common terminals of the Centre and Right switches.

Thanks, I will try this in the next day or so and revert.