New Switch With Only One Live Input – How to Handle Two Live Wires?

[u/-TheLonelyChild]

Heya~

I’m trying to replace my old 2-gang switch with a Sonoff ZBM5 2-gang switch, but I ran into an issue:

My current switch has two live wires (one for each gang).

The Sonoff module only has one live input.

I’m not sure what to do with the second live wire. Can I just screw it into an empty slot on the Sonoff, or do I need to combine the wires somehow?

Thanks in advance!

[u/Lazy-Philosopher-234]

I love when all the wires are the same color and the question is "how can I do this?" without even hinting at using a tester to start making sense of the monochromatic mess.

[u/Byjugo → u/Lazy-Philosopher-234]

This sub makes me wonder why these houses have not burned down…. Yet…

[u/ep50 → u/Byjugo]

In the all powerful breaker we trust

[u/Byjugo → u/ep50]

A breaker won’t work if the wiring isn’t connected…

[u/Turbulent-Pea-8826 → u/Lazy-Philosopher-234]

I see the OP also had my electrician except my dude used all black.

[u/95beer → u/Lazy-Philosopher-234]

Wouldn't it be normal for this to be all red? There is no neutral or earth shown in the picture. There is an incoming live, a bridge for that live, and an outgoing live in the 2 different (higher) L spots. Then there are the 2 switched lines for the lives of the lights (lower spots).

I'm not from whatever country is shown, but that seems to match up with what we'd expect here

[u/SnooPears1903 → u/95beer]

Switched active supposed to be marked here it's usually white and red is a permanent active

[u/Consistent-Hat-8008 → u/95beer]

It doesn't matter what's normal. Unless you just wired it, assume no wire color correlates to its function. Always test, never guess.

[u/95beer → u/Consistent-Hat-8008]

Sure, but it is better to have a hypothesis to test against. Then if you can't figure out why it is that way, you call in a professional

[u/Consistent-Hat-8008 → u/Lazy-Philosopher-234]

The answer is "hire a handyman because you're clearly not equipped to deal with mains power if you have to ask basic questions online".

[u/Connect_Wrangler5072]

Get an electrician in to do it !

[u/SomeDumbPenguin]

If you're just powering lights, one line should be able to handle the wattage requirements, particularly if you have replaced your lighting with LED.

You should be able to just cap one off with a wire nut & you can wrap it with electrical tape to make sure it doesn't go anywhere. An extra bonus would be to do the same on the other end of the line, if you can.

[u/umognog → u/SomeDumbPenguin]

This is not good advice.

Its a ring circuit, not a radial.

Can see in pic 1 the hot comes in to SW1, jumper hot wire to SW2 and a hot wire out.

There are then 2 further switched wires.

As far as live goes, switched lives need to go to S1 & S2 on the sonoff, the two lives need to go into a wago and the jumper could be reused from the wago to the live in on the sonoff.

OP has a big problem though that there is no neutral at the socket from the photo, which makes the ring part really weird because if its at the ceiling rose, the switch should not be wired up in series like that but should have the 2 feeds and return switches sleeved.

Edit; spotted the neutral is optional, but im still personally bothered that the two hot ins are wired together like that.

[u/SomeDumbPenguin → u/umognog]

I was going with OOP knowing what they are talking about with two hots. I figured if there is only one hot and that's a jumper to supply power elsewhere, then doing what I suggested wouldn't hurt & they'd realize things later when they found some stuff that wasn't working... It's not really a "Bug problem" though, I was trying to give a simple step to help them forward

[u/SuperS06]

How to handle two live wires ? The correct answer starts by figuring out why there are two live wires instead of just one. Then maybe you can decide to remove one of them because you've identified which and why.

If you're not competent to figure it out, don't do it.

[u/SuperS06]

Actually just looked at the picture and I don't see two live wires.

This looks like it's 1 live wire that's bridged between the two switches and leaves to somewhere else after that.

[u/95beer → u/SuperS06]

Exactly, so you'd just take out the bridge (the little wire) and put both of the remaining live wires (incoming and outgoing lives) into the new live wire spot. Easy as

[u/WarmCat_UK → u/95beer]

OP: Here is the correct answer!

[u/JS17]

OP, maybe I’m wrong, but if you’re in the UK, or somewhere outside of the US, don’t trust most replies here.

[u/mckulty]

If there's no other switch in series, 110V is 110V. Tape one use the other.

[u/andyrocks → u/mckulty]

That's a 220v circuit.

[u/mckulty → u/andyrocks]

It would have been good to mention that. Is it true?

So the DIY solution would be tie 'em together into one feed, right?

JK JK JK

[u/OG_MilfHunter]

Pull out the manual for your old switch and start piecing together clues. I believe in you.

^{I also believe in ghosts, so don't get too excited.}

[u/CRM-3-VB-HD]

Don’t just tie the two hot wires together; you might burn your house down. Please get professional help if you are not experienced in handling line voltage wiring. It is extremely dangerous and potentially deadly. Seriously, don’t mess around if you don’t know what you’re doing.

[u/IdoCyber]

Call an electrician.

[u/zedsmith]

You only need supplied power from one. Just connect your two loads and one line. Cap the other.

[u/SnooPears1903]

Get another piece of same gauge wire then use a wire nut or screw connector to combine the two cables together also connect the extra piece of wire you have with these two wires to create a pigtail and put a connector over the three cables twisted together and use the third cable you added as a pigtail to go into the smart switch active

Alternatively you can shove the two wires into the line side of the switch but I don't recommend that as these have fairly small termination blocks so you won't be able to do a good connection

[u/sgtm7]

What brought you to the conclusion that there are two live wires? With the switch turned off, if you remove that jumper, and check voltage, do you have voltage on two different wires?

[u/sh1be]

L1 and L2 is where you plug both your live wire (one for each port), and L is your common. You can plug both common into the L.

edit: Your common on the old switch is the top 2 wires, because they're chain together. The live wires are the bottom 2 on the old switch.

[u/pnlrogue1]

UK user? Some of our older sockets are wired with just the live wire. You have to buy special sockets for no-neutral wire installations that (usually) have a battery in them.

Honestly, you're probably going to want to pop a re-wire on the shopping list as you're probably overdue one...

[u/Chris_Blue_72]

This is almost certainly UK looking at the backplate. 240VAC light ring. The Incoming Live ring is bridged to the outgoing live ring. Then two switched live wires going to two lights.

[u/NervousOrange1796]

There are so many wires, even the same color. As other comments have said, it might be better to find a professional electrician to solve it.

[u/MetehanDev]

You either can combine these 2 wires together and put it into sonoff device, they will act together as one or you can get a 2 channel compatible device for your 2 gang switch.