Two way switch nightmare!!!

[RafTheman]

Hi,

This forum has helped me out a few times over the years, but this is my first post and I hope you can help!

I have recently bought the property next door to mine and knocked a wall through upstairs to make a large living room. The room now has a light switch and bulb on each side, on two completely different circuits and boards as they are from different properties.

I am trying to convert the switches so that each switch turns both lights on and off. I am trying to do this using one gang two wat switches on each side and connecting the switches using three core cable.

It's not working, I'm only getting one bulb to work and even that is not working two way!

I am unable to connect the lights together as it makes the job a whole lot messier; I.e. cutting up the ceilings. Thats why I'm trying to connect the switches using three core going under the floor boards.

Any help will be greatly appreciated and diagrams of what I need to do would be very very appreciated!

 

[plugwash]

You MUST NOT make any form of electrical connection between two light fittings that are on different circuits. Doing so could be EXTREMELY DANGEROUS to anyone working on the system in the future.

If you really can't get access to the light fittings my advice would be to install two two gang two way switches and have a seperate two way system for each light (so two runs of 3+E between the switch positions).

 

[bernardgreen]

STOP

What you are attempt to do could be extremely dangerous,

By interconnecting the Lives from two separate properties on separate supplies you could create a short circuit between two different phases. That is short circuit on 440 volts.

 

[ban-all-sheds]

I have recently bought the property next door to mine and knocked a wall through upstairs to make a large living room.

When you applied for Building Regulations approval, what did you say would be the way that you'd ensure the electrical work would comply with Part P?

Did you by default agree to any LABC assumptions about it being done by a qualified electrician? If so you really must go down that route, or agree a change with your BCO, or the words rock and hard place will be featuring before too long.

The room now has a light switch and bulb on each side, on two completely different circuits and boards as they are from different properties.

Stop.

Now.

Get things onto the same CU before you do any more connecting them together.

If they've got RCDs, have you not thought about what will happen when you connect two circuits together?

Do you even know if the two properties are on the same phase? You so do not want to find out the hard way that they are not

I am trying to convert the switches so that each switch turns both lights on and off. I am trying to do this using one gang two wat switches on each side and connecting the switches using three core cable.

It's not working, I'm only getting one bulb to work and even that is not working two way!

Do you actually know how 2-way switching works?

Do you have, and know how to use, a multimeter?

I am unable to connect the lights together as it makes the job a whole lot messier; I.e. cutting up the ceilings. Thats why I'm trying to connect the switches using three core going under the floor boards.

That won't work.

Any help will be greatly appreciated and diagrams of what I need to do would be very very appreciated!

Lighting is fully explained in the Wiki, but I you really must get an electrician - the potential consequences if the two sides are on different phases are catastrophic.

 

[bernardgreen]

I am unable to connect the lights together as it makes the job a whole lot messier; I.e. cutting up the ceilings.

If you have

knocked a wall through upstairs to make a large living room

and done this properly and safely then cutting a ceiling for wiring will be trivial by comparison.

However it might be that you have a death trap.

Did you make certain the wall was not load bearing ? If it was have you inserted the necessary steels or large section timbers to support the structure ( floor, ceiling roof etc ) that the wall was supporting when you removed it.

Structures may collapse months or even years after a supporting wall has been removed and no replacement supports installed.

 

[RF Lighting]

Do you even know if the two properties are on the same phase? You so do not want to find out the hard way that they are not

Trust me it goes with a right bang The fault current on a phase to phase connection can be horrendous.

 

[ban-all-sheds]

I know. Not from personal experience, but I do know.

Hence why I told the OP he did not want to find out the hard way....

He's gone a bit quiet - let's hope it's not for a bad reason.

 

[securespark]

You need to disconnect the existing light in the room you've knocked through to. Keep the loop intact, though for the rest of that circuit.

Then you need to extend the switch wiring and lighting into that room, but fed from the other houses circuit, so that there is no short circuit in the switching.

Best get a sparkie in.

 

[bernardgreen]

Trust me it goes with a right bang The fault current on a phase to phase connection can be horrendous.

At least that is error current is probably limited by a protective device. It is the neutral to neutral currents between two different supplies that worry me as they have no fusing.

 

[rjm2k]

Why would you do this at all? Surely if you have joined the 2 properties into 1 you will want a single electrical supply and a single bill (standing charges etc) rather than 2?

 

[dhutch]

Why would you do this at all? Surely if you have joined the 2 properties into 1 you will want a single electrical supply and a single bill (standing charges etc) rather than 2?

Glad im not the only one thinking this!

However it may be that the incoming feed from one property has been routed to supply the other, without moving/combining the boxes. Ie, they are now on the same phase but from two CUs

Eitherway however, they need to be on the same circuit from the same CU. Depending how its been wired it may be possable to do the work without replacing the wires from the switch to the light but you can tell without knowing whats there.


Daniel

 

[ban-all-sheds]

However it may be that the incoming feed from one property has been routed to supply the other, without moving/combining the boxes. Ie, they are now on the same phase but from two CUs

It may be.

Would you want to bet your life on it having been done, without having it checked by someone who knows what they are doing?