2 way wiring, lighting fed from two locations

[phmetcalfe]

hi,

Removed some old wiring from a garage and simplified the electrics but in doing this i disconnected the feed from the garage for the outside lights around the house and cannot work out how it even worked before, this is what i know.

House has 4 lights which go back to a junction box somewhere that i cannot find, a 2 way switch with 3 core + earth connected in the usual manner l1 Yellow, L2 Blue, C as red, this cable then goes into the loft and must connect to the 5 lights before going out and into the garage (used meter to confirm this as same cable) but the cable is not live on any contact in the house since i terminated the other end in the garage. But in the garage it had a 2 way switch and fed two more lights which i have found the 2 core for + earth.

Any idea how to re-wire this mess back up so the switch in the house switches all the lights back on, it did work so is possible but i cannot work it out.

regards

Peter

 

[Space cat]

Let's clarify this a bit. You have a three core and earth cable dangling in the garage and its cores are connected, like for like, with the ones in the house switch. None of these are live. You also have a flat twin and earth cable dangling in the garage which, you assume, feeds two more lights. All the lights used to go on and off together.

To make this work you must have a permanent live somewhere. My guess would be that the flat twin and earth is in fact live feed and switched live. You'll need to find out for sure before you go any further. If this is the case then proceed as follows:

Connect the three cores of the first cable to the switch terminals just as they are at the house end. Connect your live feed THROUGH A LIGHT BULB to either L1 or L2 and switched live to the other one. If everything is working correctly you should find that your switches control the extra bulb as expected and that your other lights glow dimly at the same time. If they are too dim to see, take some of the bulbs out.

There is a chance that the outside lights are not on the two core cable at all but come directly from a junction box somewhere along the three core cable. In this case you might find that your test bulb and outside lights are always on. Swap the live feed and switched live between L1 and L2.

When you're 100% sure that everything works as it did before, replace the test bulb with a direct connection.

 

[phmetcalfe]

yes 3 core with bare earth cable dangling which is not live and is connected like for like in the house switch which also is not live.
Also have 2 flat twin & earth cables which are connected to each other in juctions box neither of which is live, i put la ive feed onto these live to live and neg to neg and the lights outside the garage came on so assume these are the feeds for the outside lights.

any ideas thanks for the fast reply.

 

[Space cat]

Also have 2 flat twin & earth cables which are connected to each other in juctions box neither of which is live, i put la ive feed onto these live to live and neg to neg and the lights outside the garage came on so assume these are the feeds for the outside lights.

Well that's pretty conclusive but now comes the crunch question. In the original setup, where did the power come from? Possible answers:

1) There's a live terminal somewhere in the garage that you've overlooked. Did you remove any cables from any other switches or boxes?

2) One of the three cores in that dangling cable was live but a fuse has gone.

 

[phmetcalfe]

yes there was a feed into the box. which also had the feeds for outside lights, the 3 core and a feed from mcb. Checked all fuses on the MCB in the house and garage none have blown, also the outside lights are not on a fused switch, they were in fact on an old style switch which was cracked when i opened it to check the cables for a live feed, i think that there should be a fused switch on the feed for these whereever it may be.

I will as best from memory describe the old wiring arrangement to see if it can give you any clues.

3 core from house comes into a junction box, then joins to another 3 core like for like, it then goes into the 10 way connector box, in this box was feed from garage MBC, feeds for outside lights, feed for internal lights and an outgoing 3 core which when to a junction box 2 cables of 3 core came out one to an external wall switch the other to intermediate switch, out of the intermediate switch it went to the other end where i found the common and blue wire taped yes taped together. this came about as the internal lights wern't working so i ripped out all the 3 core bar the one from the house which i didn't reliase at the time as i assumed so all for switches at each end and outside one. also the new lights in the room built in the garage were not working, much to my horrow discovering that the guy had modified 2 core + earth to 3 core - earth using the bare earth as a live made me somewhat nervous about the state of the electrics.

 

[phmetcalfe]

also not to mention the live feed for garage and the 3 core are standard cable 2m above a pathway taped to a rusty old unearthed metal conduit (think part p says single cable has to be 4.5m), so if they don't work i will suggest to the guy about putting armour cable in from a box where it comes out of the wall, label the MCB with the caution two colours in use, then rip out the old wires which ain't live terminate and blank off, then get a load of flex n conduit wire in 5 new lights off a 5amp RCD fused switch located where he likes and get the local electrician to sign it off (am self certified so only do simple circuits)

 

[Space cat]

To recap ---

You have a dangling three core plus earth cable that you can trace back to a switch in the house. It may or may not stop off at junction boxes along the way.

You have two twin and earth cables that go directly to two outside lights. You've proved that these work because you've put power on them. You want these lights to be controlled by the house switch. You can have a second switch in the garage on that dangling cable if you want it.

You have a live two core and earth cable fed by a breaker in the garage that you can use for lights.

You have more outside lights (two, three or four) whose cables go somewhere out of sight. I suspect that the dangling three core cable does stop off at a junction box and this is how those lights originally got their power. They worked once from the house switch and you want to use them again on the same switch - along with the other two lights whose cables you know about. All the lights will go on and off together.

The supply from the house to the garage is an accident waiting to happen!

 

[phmetcalfe]

yes that is all correct, now the question is how do i wire all this together to make it work again, its a mess and is a bit unusual in the manner it is done,

thanks

 

[Space cat]

The wiring at the garage end isn't too difficult and I'll explain it when I get a bit more time. Meanwhile you have another problem. The three core cable that is a vital part of the two way switching is, to use your own words, "2m above a pathway taped to a rusty old unearthed metal conduit". That's not good!

 

[phmetcalfe]

right thank you, i will put it into plastic conduit across the pathway which should be ok when its anchored at each end.

 

[Space cat]

I've just spotted another potential problem. You have a number of lights that were once controlled by the two way switches. Now it's a jolly good bet that their live connection originally came in on one of the garage switch terminals but where is their neutral connection? It's quite likely to be tied in with the neutrals for a whole load of other lights inside the house.

The problem is that the live supply for these lights needs to come from the same circuit. From your description so far, you only have one twin core and earth cable supplying power to the garage. Is this an extension of that lighting circuit? You mention a breaker in the garage. Is this a single pole breaker or is it in a mini consumer unit with two pole isolator - or even an RCD? If you take power from an RCD protected circuit, you must connect the neutral side back to the same circuit or it will trip. The same rule applies to an isolator if you want it to truly isolate.

Things are not looking so simple after all. You need answers to two questions:

1) Where are the neutrals for those outside lights connected?

2) Where does that live supply to the garage come from?

I would want those outside lights to have their own fused supply, either spurred off a ring or direct from a dedicated fuse/breaker in the CU.

the outside lights are not on a fused switch, they were in fact on an old style switch which was cracked when i opened it to check the cables for a live feed, i think that there should be a fused switch on the feed for these whereever it may be.

Are these the two lights whose cables you have identified?

 

[phmetcalfe]

yeah, this is where i got stuck, the neutral connection, the whole house is protected by an RCB unit, which is a pain as it trips just as a bulb is about to blow and everything goes off. In the garage it has an old style wired fuses box with a 15amp one for the lighting (bit high if you ask me)

In the house are main incoming fuse, then RCD then it goes out to two MCU's, the garage and what i hope the outside lights are fused on the bottom board so in theory the neutrals will come back and meet inside this board therefore loosely being in the same circuit, so to test this which wire do i need to put current on using your light method then the lights should work

1) Where are the neutrals for those outside lights connected?
bottom MCU - i an sure they are on this one will check tomorrow,

2) Where does that live supply to the garage come from?
bottom MCU

I would want those outside lights to have their own fused supply, either spurred off a ring or direct from a dedicated fuse/breaker in the CU.

 

[Space cat]

so to test this which wire do i need to put current on using your light method then the lights should work

Put a two way switch on the end of that dangling three core in the garage, copying the connections you have at the house end. Isolate any other dangling wire ends whose origin you don't know in choc block.

Now connect the test bulb between the live supply you hope to use and each of L1 and L2 in turn. One of these will (should!) bring the test lamp on all the time; the other one will (should!) allow you to switch it from either end. Check that the outside lights are getting some voltage, even if they're too dim to see, or take some bulbs out until you can see them. If full voltage appears across your test bulb you have a short somewhere.

 

[phmetcalfe]

ok so connect two way switch like for like on 3 core,

then take my live feed and connect it to a lamp holder with bulb, then take feed out the other side into L1 and L2, one of these will keep the bulb on and the other will make it so that i can switch it from either switch. The bulb should glow dimly along with the outside lights. Once i have identified these we can then work out the wiring sequence. Will do that on monday and let you know thanks

have a nice weekend