Electric light switch botch up?

[proton]

This switch had to be replaced as bathroom light downstairs was not coming on,  switch on left was not working. One on right controls light on the stairs up top. When done the bathroom then worked, but not until bloke with screwdriver had left did I notice you could now no longer switch the stair light on then off upstair, if switched on upstair it would not switch off down stairs, so he's wired it up wrong somewhere. Now the one upstairs will not come on at all, not the bulb, and it was always flickering a bit after the new switch was put in.  Bloke is not worth getting back, not a real electrician. Can anyone see an obvious fault in this wiring configuration? 

 

 

[Crossy]

Did he replace both switches or just the faulty one?

 

 

[bearded_bluto]

40 minutes ago, proton said:

... if switched on upstair it would not switch off down stairs,.. always flickering a bit after the new switch was put in....

I think your talking about a "(X2) Single Pole, Double Throw" switches. If two switches control one light, and you have some flickering or one stays lit very dim you may have induction on one of the wires, usually half voltage, so around 110 with multi meter.

I cant comment on this since I can only do this wiring myself and only if I draw everything out on paper and label wires. There is a bunch of smarty pants on this forum though. :-)

[Hawaiian]

16 minutes ago, bearded_bluto said:

I think your talking about a "(X2) Single Pole, Double Throw" switches. If two switches control one light, and you have some flickering or one stays lit very dim you may have induction on one of the wires, usually half voltage, so around 110 with multi meter.

I cant comment on this since I can only do this wiring myself and only if I draw everything out on paper and label wires. There is a bunch of smarty pants on this forum though. 🙂

I'm pretty good at plumbing, except for PEX systems.  My plumbing contractor friend taught me how to properly solder copper pipes and just about everything in the plumbing code.  When it comes to electrical wiring, I leave it to qualified experts.

[proton]

58 minutes ago, Crossy said:

Did he replace both switches or just the faulty one?

 

 

 its all together one unit

[proton]

33 minutes ago, bearded_bluto said:

I think your talking about a "(X2) Single Pole, Double Throw" switches. If two switches control one light, and you have some flickering or one stays lit very dim you may have induction on one of the wires, usually half voltage, so around 110 with multi meter.

I cant comment on this since I can only do this wiring myself and only if I draw everything out on paper and label wires. There is a bunch of smarty pants on this forum though. 🙂

 

Yes that makes sense, I want to get a qualified man in, as usual mrs wants to go through the usual route- brother in law, man who cleans the air cons, security guard etc before we get to that stage.

[Crossy]

I suspect that you have actually got two single-pole one-way (on-off) switches, whereas, as noted above, you need at least one of them to be two-way.

 

If you still have the original switches, take the faulty one to your local electrical outlet and try to source a replacement.

 

[sometimewoodworker]

3 hours ago, proton said:

 its all together one unit

No. There are 2 switch units that push into a backplane, so you can swap out 1 or both.

[chickenslegs]

1 minute ago, sometimewoodworker said:

No. There are 2 switch units that push into a backplane, so you can swap out 1 or both.

Yes. And I'm wondering how that unit fixes to the wall. There doesn't appear to be any backbox.

[proton]

1 hour ago, chickenslegs said:

Yes. And I'm wondering how that unit fixes to the wall. There doesn't appear to be any backbox.

 

There are screws to fix it in

[RocketDog]

15 hours ago, bearded_bluto said:

I think your talking about a "(X2) Single Pole, Double Throw" switches. If two switches control one light, and you have some flickering or one stays lit very dim you may have induction on one of the wires, usually half voltage, so around 110 with multi meter.

I cant comment on this since I can only do this wiring myself and only if I draw everything out on paper and label wires. There is a bunch of smarty pants on this forum though. :-)

Both top and bottom switches must the single pole double throw.

 

Inductance has absolutely nothing to do with it. There may be some leakage somewhere in the wiring or even capacitive coupling bit these would only allow minimum current that might partially light very low current devices.

 

My bet is that the switches are wrong. The two wires from the light go to the center poke on both switches. The two power wires go to the other two switch contacts. Draw a diagram and you'll see.

 

 

[bearded_bluto]

14 minutes ago, RocketDog said:

Both top and bottom switches must the single pole double throw.

 

Inductance has absolutely nothing to do with it. There may be some leakage somewhere in the wiring or even capacitive coupling bit these would only allow minimum current that might partially light very low current devices.

 

My bet is that the switches are wrong. The two wires from the light go to the center poke on both switches. The two power wires go to the other two switch contacts. Draw a diagram and you'll see.

 

 

No, if you throw the switch on left you have two lives (line(s)) going to your light, not good.

edit: oh wait your saying you think this is the mistake in your drawing? You may be right then, I was thinking (behind the walls) inductance reasoning as to save wiring they may have used the ground wire in the middle for something other than ground if they used AC wiring with 3 wires and not the usual 2 (the usual for lights) L&N.

 

Ask me how I know. lol (I did this and mine stay dimly lit depending on the type of light) lesson learned. lol

[RocketDog]

6 minutes ago, bearded_bluto said:

No, if you throw the switch on left you have two lives (line(s)) going to your light, not good.

Wrong. No current flow if light is connected to both line or neutral at the same time.

 

Of course both switches should be fed from the same breaker.

 

Current will only flow thru the light if one side is line and the other is neutral. Line to line or neutral to neutral there is no potential difference  so no current flow.

 

Check it out on the web about how double pole light circuits work.

 

Maybe Crossy will come along to convince you.

 

I spent over 55 years as an electronic computer circuit designer. I've also wired numerous switches this way. In DC circuits such an arrangement is used to switch polarity for reversing DC motors for instance.  Think about it more and you'll see it.

 

Change line and neutral to plus and minus and you'll see.

 

Good luck.

[bearded_bluto]

33 minutes ago, RocketDog said:

Change line and neutral to plus and minus and you'll see.

 

Good luck.

Thanks, I believe you, I like to learn.

 

Edited:

I was thinking what happens if one wire is longer, would that cause the 50hz to not osculate at the same time? Just wondering if both Lines would be in sync. I can see no problem with DC like you said for PC circuit boards, just curious,

[Crossy]

There are a number of ways of wiring 2-way (3-way to our friends across the pond) light switches. All need two 2-way (single-pole double throw) switches.

 

Here's a more conventional representation.

 

 

As noted earlier @proton do you still have the old switches? If so trot down to your local electrical supplier and get a replacement module for the faulty one.

 

Photos of the switch at the other end of the 2-way arrangement would be useful. 

 

Also, just to be sure, can you take a photo of the back of one of your new switches, they usually have a representation of the internal wiring.

 

 

 

[bearded_bluto]

33 minutes ago, bearded_bluto said:

Thanks, I believe you, I like to learn.

 

Edited:

I was thinking what happens if one wire is longer, would that cause the 50hz to not osculate at the same time? Just wondering if both Lines would be in sync. I can see no problem with DC like you said for PC circuit boards, just curious,

I can't edit my comment, but I just thought about another issue perhaps, some bloke like myself will someday assume the light is off to do something to the fixture of that light, grab a chair/ladder, get on chair/ladder with bare feet and proceed to plug in meter to both wires, ahh zero volts, get good ol screwdriver out and then if both switches happen to be Lines I get a rude awakening. lol

[ardsong]

deleted as the answer is already given

 

 

[proton]

30 minutes ago, Crossy said:

There are a number of ways of wiring 2-way (3-way to our friends across the pond) light switches. All need two 2-way (single-pole double throw) switches.

 

Here's a more conventional representation.

 

 

As noted earlier @proton do you still have the old switches? If so trot down to your local electrical supplier and get a replacement module for the faulty one.

 

Photos of the switch at the other end of the 2-way arrangement would be useful. 

 

Also, just to be sure, can you take a photo of the back of one of your new switches, they usually have a representation of the internal wiring.

 

 

 

 

Dont have the old switches but took it up to the shop originally and he obviously sold me the wrong thing, thanks for the help. Will have to get a real electrician in

[sometimewoodworker]

1 hour ago, bearded_bluto said:

I can't edit my comment, but I just thought about another issue perhaps, some bloke like myself will someday assume the light is off to do something to the fixture of that light, grab a chair/ladder, get on chair/ladder with bare feet and proceed to plug in meter to both wires, ahh zero volts, get good ol screwdriver out and then if both switches happen to be Lines I get a rude awakening. lol

That is why you, as a neophyte, should use more than 1 test device, if you add a 30 baht neon screwdriver (I know it’s probably an LED now) then it will light up, even though your meter shows nothing. The other thing you should do is wear safety 😉 filopflops and if possible keep one hand in your pocket. Both of these precautions will be enough to probably reduce a shock to a minor disturbance and as long as it doesn’t cause you to fall off the ladder you will continue to live a long time. I can’t remember how many shocks I have got, probably single or low double digits, & maybe even none in Thailand, but every one was an uncomfortable reminder that I probably hadn’t followed my own advice not to touch the bitty bits.

[RocketDog]

3 hours ago, bearded_bluto said:

Thanks, I believe you, I like to learn.

 

Edited:

I was thinking what happens if one wire is longer, would that cause the 50hz to not osculate at the same time? Just wondering if both Lines would be in sync. I can see no problem with DC like you said for PC circuit boards, just curious,

In general even connecting Line from two different breakers is OK since for houses since only a single phase comes in to the load center so all subsequent circuits will be in phase.  It is not recommended practice though.

Although load power factor may change each branch circuit  phase very slightly there is too small a difference to cause problems.

[RocketDog]

1 hour ago, sometimewoodworker said:

That is why you, as a neophyte, should use more than 1 test device, if you add a 30 baht neon screwdriver (I know it’s probably an LED now) then it will light up, even though your meter shows nothing. The other thing you should do is wear safety 😉 filopflops and if possible keep one hand in your pocket. Both of these precautions will be enough to probably reduce a shock to a minor disturbance and as long as it doesn’t cause you to fall off the ladder you will continue to live a long time. I can’t remember how many shocks I have got, probably single or low double digits, & maybe even none in Thailand, but every one was an uncomfortable reminder that I probably hadn’t followed my own advice not to touch the bitty bits.

Neon is still used for those detectors because the ionization voltage is about 95V but current is micro amps. So even it's capacitive coupling only that allows such current to flow literary through your body to grounded.

 LED currents are generally in at least the milliamp range. To light one of those would require much more body capacitance and this be dangerous, about a thousand times more current than neon needs to ionize.

[bearded_bluto]

1 hour ago, sometimewoodworker said:

That is why you, as a neophyte,

Thanks gramps, dont forget your pills in the morning. I don't assume everybody is a retard, you might be surprised. 100% sure I am a neophyte in your sawmill.

[BritManToo]

4 hours ago, RocketDog said:

Both top and bottom switches must the single pole double throw.

 

Inductance has absolutely nothing to do with it. There may be some leakage somewhere in the wiring or even capacitive coupling bit these would only allow minimum current that might partially light very low current devices.

 

My bet is that the switches are wrong. The two wires from the light go to the center poke on both switches. The two power wires go to the other two switch contacts. Draw a diagram and you'll see.

 

 

There is no neutral in light switches!

[RocketDog]

8 hours ago, BritManToo said:

There is no neutral in light switches!

Very observant.

Double throw switches SPDT do however have a single pole contact. They are not interchangeable like SPST switches.

 

Those are labels of the wires connected to the switch. As in Line and Neutral.

You know...those voltage things.

[sometimewoodworker]

23 hours ago, RocketDog said:

Neon is still used for those detectors because the ionization voltage is about 95V but current is micro amps. So even it's capacitive coupling only that allows such current to flow literary through your body to grounded.

 LED currents are generally in at least the milliamp range. To light one of those would require much more body capacitance and this be dangerous, about a thousand times more current than neon needs to ionize.

You are wrong that LEDs are not used in the test screwdrivers 

Though they do require batteries. The green is from touching both ends, the green has and red shows an active line socket.

So the ways they detect are slightly different.

[sometimewoodworker]

23 hours ago, BritManToo said:

There is no neutral in light switches!

That depends in the wiring and the switch. I have some light switches that require a neutral, so those switches have neutral in the  wall enclosure.

[Fruit Trader]

On 1/11/2025 at 12:30 PM, RocketDog said:

LED currents are generally in at least the milliamp range. To light one of those would require much more body capacitance and this be dangerous, about a thousand times more current than neon needs to ionize.

 

The current would be in the microamp range if a LED was used as a mains tester.

Consider the following :-
 

 

 

A much safer method for test screwdrivers is to drive a LED with a battery and detect mains voltage with a sensitive transistor circuit.

 

 

[RocketDog]

20 hours ago, sometimewoodworker said:

You are wrong that LEDs are not used in the test screwdrivers 

Though they do require batteries. The green is from touching both ends, the green has and red shows an active line socket.

So the ways they detect are slightly different.

Of course. Note the batteries. Sure it can be done, but the cheapest, most common, and most reliable are the simple neon light and current limit resistor. This type a has been around for many decades.

If the voltage is enough to light neon then it's likely to be enough to hurt you. The electronic led versions can sense lower voltages though.

 

What do the LED sense of the cells are dead? No light means no voltage? I wouldn't trust it.

 

Also, I dislike renewing batteries every time I want to use something. I fail to see the advantage.

 

But...

 

To each his own.

[RocketDog]

17 hours ago, Fruit Trader said:

 

The current would be in the microamp range if a LED was used as a mains tester.

Consider the following :-
 

 

 

A much safer method for test screwdrivers is to drive a LED with a battery and detect mains voltage with a sensitive transistor circuit.

 

 

Will microamps drive an LED  directly as your circuit implies, 0.44mA?