The Lemon Fool

My daughter has just bought her first house. Inevitably there are a number of relatively minor DIY tasks to do.

One of them is to sort out access to the loft (fit a loft ladder, boards, etc). There's already a light wired into the lighting circuit. The switch is inside the loft. The light only switches ON if the landing light is switched OFF.

Before I start investigating, does anyone have any suggestions of what to look for?

I assume you want the loft light to come on when the landing light is on? You don't actually say.

I'd guess the landing light switch is a 2-way linked with a downstairs switch, with the loft light piggybacked onto it. In which case it's probably piggybacked to the wrong terminal(s).

Scott.

swill453 wrote:I'd guess the landing light switch is a 2-way linked with a downstairs switch, with the loft light piggybacked onto it. In which case it's probably piggybacked to the wrong terminal(s).

If this is the case, try throwing both the downstair and upstair switches to see when the loft light comes on. (The only way I can think of where this could happen is if the two-way circuit is wired the "old" way like it used to be done when single wires were used.)

Do the lights come on full brightness?

Julian F. G. W.

jfgw wrote:

swill453 wrote:I'd guess the landing light switch is a 2-way linked with a downstairs switch, with the loft light piggybacked onto it. In which case it's probably piggybacked to the wrong terminal(s).

If this is the case, try throwing both the downstair and upstair switches to see when the loft light comes on. (The only way I can think of where this could happen is if the two-way circuit is wired the "old" way like it used to be done when single wires were used.)

Do the lights come on full brightness?

Given the comments on the thread 'Interaction between taps and lights', maybe the OP ought to try turning on the taps in the kitchen to see if that helps.

Dod

Dod101 wrote:
Given the comments on the thread 'Interaction between taps and lights', maybe the OP ought to try turning on the taps in the kitchen to see if that helps.

Dod

swill453 wrote:I assume you want the loft light to come on when the landing light is on? You don't actually say.

I'd guess the landing light switch is a 2-way linked with a downstairs switch, with the loft light piggybacked onto it. In which case it's probably piggybacked to the wrong terminal(s).

Scott.

What Scott says....

Lights generally have a permanent live from fitting to fitting, a neutral from fitting to fitting, and a Switched live which is a wire from the permanent live to the switch(es) then back up the other core in the same cable into the ceiling rose. This switched live (and the neutral are connected to the light fitting.

The loft light is probably tapped off the landing light ceiling rose. The loft light switch should be fed from the permanent live, but is on the switched live. If you have an electrical screwdriver with a neon light, you can find the permanent live by testing the terminals whilst someone switches the landing light on and off and move the connection over.

If the landing light is twin switched there might be a lot of wires in the rose already, so it might be easier to reroute the loft feed from a bedroom light fitting

On the offchance it is tapped into the back of the landing light switch then it wants to go on the single input terminal, not one of the switched ones, unless it in into an intermediate switch, in which case it will never work properly.


Paul

DrFfybes wrote:Lights generally have a permanent live from fitting to fitting, a neutral from fitting to fitting, and a Switched live which is a wire from the permanent live to the switch(es) then back up the other core in the same cable into the ceiling rose. This switched live (and the neutral are connected to the light fitting.

The loft light is probably tapped off the landing light ceiling rose. The loft light switch should be fed from the permanent live, but is on the switched live. If you have an electrical screwdriver with a neon light, you can find the permanent live by testing the terminals whilst someone switches the landing light on and off and move the connection over.

That would be the obvious reason except that,

chas49 wrote:The light only switches ON if the landing light is switched OFF.

While it would be easy to wire something up like this on purpose, I find it difficult to understand how this could be done accidentally.

Is the landing light on a two-way switched circuit (or three-way, four-way, etc.) or is there just a single switch that controls it?

What sorts of lights are they? CFL? LED? GLS?

Julian F. G. W.

jfgw wrote:
That would be the obvious reason except that,

chas49 wrote:The light only switches ON if the landing light is switched OFF.

.......

Is the landing light on a two-way switched circuit (or three-way, four-way, etc.) or is there just a single switch that controls it?

What sorts of lights are they? CFL? LED? GLS?

Julian F. G. W.

They're LEDs. The landing light is a two way switched circuit (dimmer upstairs, ordinary switch downstairs).

I haven't yet checked if it's the On/Off state of the landing light that affects the loft light, or the position of the upstairs switch.

I may be back with more details...

chas49 wrote:

jfgw wrote:
That would be the obvious reason except that,

chas49 wrote:The light only switches ON if the landing light is switched OFF.

.......

Is the landing light on a two-way switched circuit (or three-way, four-way, etc.) or is there just a single switch that controls it?

What sorts of lights are they? CFL? LED? GLS?

Julian F. G. W.

They're LEDs. The landing light is a two way switched circuit (dimmer upstairs, ordinary switch downstairs).

I haven't yet checked if it's the On/Off state of the landing light that affects the loft light, or the position of the upstairs switch.

I may be back with more details...

My theory:
3core+earth (3+E) has been used from the ground floor landing light switch to the upstairs landing light switch. (normal)
They've then used 3+E from the upstairs landing light switch to the ceiling rose.
Strictly speaking you only need 2core+earth between the ceiling rose and the upstairs switch, but, they threw in 3+E anyway (at first fix, probably threw one single 3+E cable from downstairs, hung a loop out of the upstairs switch box and then all the way to the landing ceiling rose)

The two switches should be wired L1 to L1, L2 to L2 and C to C (3 cores required+ earth)
The connection from the upstairs switch (live and switched live) should go L1 and L2 on the upstairs switch.
The 3rd core in the cable from the upstairs switch to the ceiling rose should not be connected.
(See http://wiki.diyfaq.org.uk/index.php/2_Way_Switching first diagram under "Standard two way switching circuit" and picture a third wire connected to the common terminals going to the landling light ceiling rose)

I reckon the muppet who did the second fix (=wired it up) has made two mistakes:

1) At the upstairs switch they've connected the redundant third wire to the common connection on the switch.
2) At the ceiling rose, they have a redundant wire hanging in space, which they decided to connect to the live side of the loft light switch.

This means that the loft light switch is only energised for 3 of the 4 possible combinations of upstairs+downstairs landing lights.

To verify this:
1) Turn on the loft light, and fiddle with the landing light switches to get the loft light to come on.

2) Go through the four permutations of the landing light switches (order is unimportant, re arrange to suit)
a) Upstairs: Up, Downstairs Up
b) Upstairs: Up, Downstairs Down
c) Upstairs: Down, Downstairs Down
d) Upstairs: Down, Downstairs Up

(While you are at it, verify that two of the combinations give you "landing light" on, to ensure the absence of other muppetry)

If you find that the loft light stays on for all but one of the combinations, then the next thing to look at is where the loft light switch live feed originates, looking out for random single choc-block connections in the landing light ceiling rose.

Note that "loop in" ceiling roses have 4 sets of terminals:
3way #1: Permanent live: Live from CU/previous rose, live to next rose, live to switch.
3way #2: Neutral: from CU/previous rose, to next rose, to the bulb
3way #3: Earth
2 way: Switched earth: from the switch, to the bulb

If an examination of the landing ceiling rose reveals muppetry in the form of a extra choc-block (a "5th terminal"), (a) move the feed to the loft switch from the choc-block to the permanent live feed on the rose. and (b) ensure the remaining wire+chocblock is taped up.
If you want to complete the job, go down to the upstairs landing light, identify the 3+E which goes up to the ceiling rose, rather than downstairs to the hallway, remove and insulate the wire which goes to the Common terminal on the switch for the landing light.

PochiSoldi

jfgw wrote:
That would be the obvious reason except that,

chas49 wrote:The light only switches ON if the landing light is switched OFF.

While it would be easy to wire something up like this on purpose, I find it difficult to understand how this could be done accidentally.

Is the landing light on a two-way switched circuit (or three-way, four-way, etc.) or is there just a single switch that controls it?

Julian F. G. W.

Chas...

I haven't yet checked if it's the On/Off state of the landing light that affects the loft light, or the position of the upstairs switch

Good point Julian, I misread that.

It could be the loft light is connected to the landing light rose between the perm live, and the switched live instead of the neutral. When the landing light is ON both feeds to the loft light are at 240V so it will not light. When the landing light is OFF then switching the loft light on allows current from perm live to switched live, via the now illuminated landing light (or hall light if on a twin circuit). Of course as Chas is in the loft he doesn't see the landing light come on.

Paul (who definitely didn't need to draw it out twice to check he thinks it could be the answer).

chas49 wrote:Before I start investigating, does anyone have any suggestions of what to look for?

The feed to the loft light switch is coming off the wrong wire (as has been detailed by others).

If the house is anywhere near Kent and you have had enough of searching then for a pint of beer I'll pop over and sort it out for you Charles.

Cheers,
Chris

It's a simple case of following the wiring back as advised and checking it with a multi-meter, to make sure a permanent live feed goes off to your landing light switch along with a proper neutral.
This is probably all tapped off the ceiling rose for the landing light as advised above. These things are surprisingly easy to screw up. The last ceiling rose I worked on had 8 red and 8 black wires going to it, considering the lighting ring and feeds to both switches (2 -way). Thankfully the switched live was identified.

You could just disconnect it and tap into the lighting ring with a suitable junction box, connected to the loft switch and light.