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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Switch wiring question
Hi,
I am having a problem with double light switch in my kitchen...and would appreciate any advice before I call out an electrician. In the kitchen I have a double switch (in a single gang faceplate) that separately operates a ceiling light and a set of under cupboard lights. The kitchen was rewired by an electrician about 6 years ago when we had a kitchen fitted. For a while this one switch has been playing up - depending on how hard/fast you switched off the under cupboard lights would either blow the lighting circuit fuse (5A) or possibly trip the whole house circuit - I say possibly because I have recently fitted a plug in trip fuse for the consumer unit (just on this lighting circuit) to avoid having to fit a new 5A fuse in the dark each time the fuse went - and now the house earth leakage circuit breaker trips out as well. This week the switch has started tripping the electric almost every time it is used. There is some soot/ burning to the inside of the undercupboard switch. The new fuse/trip device in the consumer unit is the only change.Thsi repalced the old style 5Amp fuse holder at the consumer unit with a new plug in trip type which was at 6A (Wylex to match consumer unit). This was to avoid having to replace the fuse which used to go in the lighting circuit when the undercupboard lights On inspection of the switch wiring there are two cables entering the switch backplate - both earths are connected to the metal back box. On the switch for ceiling light cavle ones red and black wire are connected to switch one COM and L1. There is a jumper wire from this switch L1 to switch 2 L1. The 2nd incoming mains cable has the neutral cable taped up (not connected) and the red cable enters switch 2 COM. There is a junction box above the kitchen cupboard that the electrican has used to extend the old switch cable to the current position. On inspection the two switch cables (from switch back box) go to this junction box and connect separately to two further cables that go to the ceiling (upstairs floor ) - connections in this junction box are cable1 neutral to neutral / cable 1 live to live ; and cable2 neutral to neutral and cable2 live to live. Earths are all connected together. This junction box looks to do no more than extend the switch cable run, The cable to the ceiling light is just that - a junction box / ceiling rose is not visible. When the kitchen was rewired the electrians had the floor in the bedroom above the kitchen up so I presume any junctions boxes are under the floorboards...and I haven't considered removing the carpet / floorboards yet to look for them. . I guess my questions are ... - Does the cabling sound right (jumper etc from switch 1 to switch 2) - Any ideas what would cause it to trip ...(this happens even if all the undercupoard lights are turned off (they each have a built in switch). - Should I go back to the old style cartidge fuse ? The trip unit on my house wiring is an earth leakage circuit breaker (my earth comes from a ground rod) . Many thanks... Nick |
#2
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Switch wiring question
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#3
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Switch wiring question
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#4
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Switch wiring question
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#6
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Switch wiring question
Yes - 4 twin and earth into the junction box - but in two pairs .
Yes the lights have all worked - for atleast 5 years. No work done in kitchen or anywhere else. Ref faulty light - see below for it still tripping with lights disconnected. I have tried disconnecting all the under cupboard lights - the electrician actually put in three drops from ceiling - which terminate in junction boxes fixed to underside of wall units. The inidivual light fittings (3) are connected to a separate junction box at the bottom of each of the three cable drops. The lights (link lights) are connected to the junction boxes - so I have disconnected each light fitting in case one of these has gone bad ....but this didn't make a difference. The only thing I can think is that one of the junction boxes under the wall cupboard has corroded inside due to moisture ingress and when the switched live is applied this trips the circuit ?? Additionally today I tried bypassing the two "extension" cables (both twin and earth) that drop from this junction box to the wall switches. For the main ceiling lights the twin and earth is suppling a live (preumably looped in from a junction box under the upstairs floor) and the black wire is as expected a switched live feed back to the light (it's not marked with red tape though). A simple test joining the black and red from cable one (which is all the switch one would do) and as expected the ceiling lights are on (once power back on of course). Based on the use of the jumper from switch 1 COM to switch 2 COM I believe the second twin and earth is actually only supplying a switched live back up to the junction box supplying the under cupboard lights. If I join the red (this must have been acting as switched live before as black wire is taped up unconnected in switch) from cable 2 to the live red from cable one I would expect the under cupboard lights to be on.....but this trips the earth leakage cicuit breaker the second the power is restored. I also tried going back to standard fuse on the circuit instead of the MCB - no differnce apart from I'm now a gew 5A fuses down. Apart from the moisture what about mice eating throug a cable - I had a brief look under floor upstairs today but no signs of any damage. Thanks so far... Nick |
#7
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Switch wiring question
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#8
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Switch wiring question
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#9
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Switch wiring question
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#10
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Switch wiring question
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