Two way lights

[opps]

Hi all

I am currently working at a mate's new home - (primarily) decorating.

He hasn't moved in yet but is getting "pressure" about that house not being finished yet.

One day I turned up stoopdily early, too early to make noise and decided to remove the old plastic 2 way, 2 gang light switch in the ground floor hallway with the new metal one. I faithfully wired in the L1, L2 and com on either side of the switch. Additionally I ran a new sleeved earth from the face plate to the back box.

The switch functioned as it should for 5 days, controlling the ground floor hallway light and the first floor hallway light. Over the weekend the electricians turned up to replace the remaining light switches and sockets with the new metal ones. They replaced the old 2 gang, 2 way switch on the first floor.

I turned up on Monday and discovered that the only lights working were the downstairs lights and the upstairs hall light (the latter had been on constantly for 2 days). None of the bedroom lights on the first floor would turn on.

The electricians had left masking tape over the metal 2 gang switch that they swapped over upstairs. Presumably to stop anyone using the switch.

Absent mindedly, when I left on monday, I went to turn the lights off as I exited. I noticed that the left hand side of the double rocker switch (which I fitted 5 days ago) no longer engages- you push it and it doesn't click in to place. I then pressed the right hand side which controls the first floor hallway light, it tripped the lighting MCB.

There are two MCBs the upstairs MCB is currently turned off since they left and will not stay open. The ground floor MCB was open until I tried to turn off the first floor light.

My gut instinct is that they wired the first floor 2 gang switch incorrectly, inadvertently mixing the wires for the ground and first floor. I have no idea if they are blaming me for the fact that the downstairs rocker switch doesn't "rock" anymore but they have known my friend for longer than I have.

Nevertheless, if anyone does point the proverbial finger at me, is there any conceivable way that my replacing the switch on the ground floor could, 5 days later, cause a problem with the switch that they replaced upstairs?

Thanks in advance.

 

[EFLImpudence]

That is difficult to follow.

If the switch does not 'rock' then presumably it is faulty - possibly damaged when the MCB tripped.

 

[opps]

That is difficult to follow.

If the switch does not 'rock' then presumably it is faulty - possibly damaged when the MCB tripped.

Sorry if I was overly elaborate. When I replaced the switch (downstairs) it functioned as it should for 5 days. Is is possible, or likely, that if the upper switch was wired incorrectly (5 days later) it would have damaged the the rocker downstairs?

In short- I swapped out a 2 gang two way light switch (downstairs) that was fine for 5 days, with the lights being turned on for at least 8 hours a day. When the upper 2 gang two way light switch was replaced by the electricians the only light upstairs that functions, but cannot be turned off, is the upper hall light, which is now powered by the downstairs/ground floor MCB and no longer the first floor MCB

When I swapped out the light switch downstairs I had to turn off both the ground and first floor MCB because there was power on both sides of the switch. Now the first floor landing light runs off the ground floor MCB (but will trip the downstairs MCB if you try to turn it off). The upstairs lighting MCB instantly trips if you try flicking it up. The downstairs hallway light will not turn on using the downstairs switch- I haven't removed the electrical tape from the upper switch to see what happens.

 

[opps]

That is difficult to follow.

If the switch does not 'rock' then presumably it is faulty - possibly damaged when the MCB tripped.

For the sake of clarity.

it the second switch on a two way lighting set up was wired incorrectly, could it damage the pre-existing switch?

 

[EFLImpudence]

When I replaced the switch (downstairs) it functioned as it should for 5 days. Is is possible, or likely, that if the upper switch was wired incorrectly (5 days later) it would have damaged the the rocker downstairs?

It could have been burnt when the MCB tipped but not your fault if it worked for five days.

In short- I swapped out a 2 gang two way light switch (downstairs) that was fine for 5 days, with the lights being turned on for at least 8 hours a day. When the upper 2 gang two way light switch was replaced by the electricians the only light upstairs that functions, but cannot be turned off, is the upper hall light, which is now powered by the downstairs/ground floor MCB and no longer the first floor MCB.

Obviously wrongly wired by the 'electricians'.

When I swapped out the light switch downstairs I had to turn off both the ground and first floor MCB because there was power on both sides of the switch. Now the first floor landing light runs off the ground floor MCB (but will trip the downstairs MCB if you try to turn it off). The upstairs lighting MCB instantly trips if you try flicking it up. The downstairs hallway light will not turn on using the downstairs switch- I haven't removed the electrical tape from the upper switch to see what happens.

Presumably the two lights were on their respective MCBs - ground and first floors; now they are not.

 

[EFLImpudence]

Do you want to rectify the problem?

If you do, post pictures of the two switches so that we can see ALL the wires and where they are connected.

 

[EFLImpudence]

if the second switch on a two way lighting set up was wired incorrectly, could it damage the pre-existing switch?

Not normally, but as the MCB has tripped then something else must have happened which could have burnt the switch.

Not normally because all wires are usually Lives so, either one of them has touched an earth or there are Neutrals present (not likely) which have been wrongly connected.

 

[333rocky333]

For the sake of clarity.

it the second switch on a two way lighting set up was wired incorrectly, could it damage the pre-existing switch?

I believe most of the time the same lamp current flows via both switches at the same time on a two way circuit,
so i would say yes, if someone shorted the upstairs switch they may well weld the contacts on the downstairs switch

 

[opps]

Update-

Got to work this morning to discover no lights. I guess someone exiting the building pressed the rocker switch that works on the downstairs 2 gang switch (resulting in the downstairs MCB tripping).

I decided to remove the now faulty 2 gang switch on the ground floor with the original plastic one (faithfully putting the wires in the same positions on the plastic switch).

I flicked on the first floor MCB and discovered that both the ground floor and first floor light come on at the same time now if one rocker is "up" and the other is "down". If the rockers are the other way around there is no light, if they are both up or both down there is no light. That is to say now no combination trips the MCB, however if I go upstairs and press the left hand rocker it will trip the MCB.

Here is a photo of the downstairs switch



When I first replaced the downstairs switch, I put little dots on each of the cables on the side of the switch that only has 3 wires. I don't think that they rewired that switch. I am guessing that they only loosened the screws to make sure that it was wired "safely".

I forgot to take a photo of the upstairs switch... I did however remove the Com from the side of the switch that has a total of 4 wires, then removed each of the light bulbs in the 3 bedroom on the first floor. I figured that removing them would break the circuit. I then flicked the upstairs MCB, it popped straight down. That, and all of the above leads me to think that one of the intermittents is in the wrong place in the first floor switch

I have no idea when the electrician are planning to return so I plan to turn up tomorrow with some long cables and my multimeter so that I can identify each of the cables by testing continuity between each of the cables upstairs and downstairs.

I believe that my understanding of two way light switches should be sufficient to identify the cables but do not be surprised if I need to refer to your superior knowledge.

Many thanks.

 

[Harry Bloomfield]

It seems these 'electricians' have probably created the mess, I would be investigating if they are genuinely qualified to be doing the job, rather than your attempting to sort the mess out yourself. If you are unsure of what you are doing, then you could make the mess a whole lot worse and perhaps have the finger pointed at you as the entire cause.

 

[opps]

It seems these 'electricians' have probably created the mess, I would be investigating if they are genuinely qualified to be doing the job, rather than your attempting to sort the mess out yourself. If you are unsure of what you are doing, then you could make the mess a whole lot worse and perhaps have the finger pointed at you as the entire cause.

That is a good point. Part of me thinks that if I sort it out then no one can potentially accuse me of having done something wrong (which I am certain that I didn't).

When it comes down to it, the electrician is a long standing family friend, I am a "pub" mate of the guy but not the rest of the wider (read: extended) family. Perhaps I should just leave things as they are, after all, the light switch that people press when they exit no longer trips the only functioning MCB. I drink in the same pub as the customer and electrician. I just don't want to find myself accused of having messed things up and thought that if I get things working as they should be I could deflect any blame. It is an "honour"/ego thing.

 

[EFLImpudence]

As the MCB trips, unless they have done something really stupid, it must be because a screw has squashed a wire against the back box or earth wire.
There are no Neutrals present to cause a short.



This is what you have and looks correct.
The top switch in the picture is not 100% clear so, first make sure I have got the colours in the correct terminals.

At the upstairs switch, you should have what looks the same but will actually be reversed, with A and B swapped.

I suspect they have got the Brown, Black and Grey cables - that is cables A and B - the wrong way round.

You will have to determine at the upstairs switch which is A and which is B, then put A in the switch with the (presumably) Brown and Blue cable.
The cable with Brown and Blue must go in L1 and L2; it doesn't matter which way round; and the Grey of cable A must go in COM, and Brown and Black in L1 and L2; it doesn't matter which way round.

Then Cable B in the other switch on its own. Grey must go in COM and Brown and Black in L1 and L2; it doesn't matter which way round.

 

[Harry Bloomfield]

That is a good point. Part of me thinks that if I sort it out then no one can potentially accuse me of having done something wrong (which I am certain that I didn't).

When it comes down to it, the electrician is a long standing family friend, I am a "pub" mate of the guy but not the rest of the wider (read: extended) family. Perhaps I should just leave things as they are, after all, the light switch that people press when they exit no longer trips the only functioning MCB. I drink in the same pub as the customer and electrician. I just don't want to find myself accused of having messed things up and thought that if I get things working as they should be I could deflect any blame. It is an "honour"/ego thing.

If the electrician is worth his salt, he will take any fault you might have created in his stride, providing you own up to it - though on the face of it sounds more like his error than yours.

 

[opps]

Update 2

Now that the downstairs 2 gang switch allows you to turn off the lights (wiring unchanged and without tripping the MCB), I decided to do as I left a few minutes ago.

I then decided to flick the two rockers on the metal switch that I removed earlier. Bizarrely, both rockers now switch properly. I have never come across that before. If a rocker switch was faced with a live cables at either end would that force it snap back if you tried to flick it in to an open position?

 

[opps]

As the MCB trips, unless they have done something really stupid, it must be because a screw has squashed a wire against the back box or earth wire.
There are no Neutrals present to cause a short.

The upstairs MCB still trips even when both face plates were loosened from their back boxes. That said, I have no idea if they did anything with the ceiling roses.

All of the lights in the house functioned fine until they turned up. Mind you so did the "saniflow" on the loo under the stairs. I tuned up Sunday and had a pee. I flushed the loo. I then watched as the water spilled over the top of the "saniflow". Fortunately most of it dripped through the bare floorboards. I then noticed that they had turned off the fused spur for the macerator and forgotten to turn it back on. TBH, I didn't know that a macerator would do that. Do people not use them during a power cut or was it possible that someone happened to be flushing away loo paper at the point that they turned it off?