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wiring heated/backlit mirror in bathroom

Discussion in 'Electrics UK' started by CanIEat, 20 Oct 2008.

  1. CanIEat

    CanIEat

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    Hi. I have a new mirror which I'm going to attempt to wire in myself. It is rated at 32W. At present there is a bathroom light with a timed extractor fan connected. All apparently wired as shown in the circuit diagram in the reference section, although I am unsure as to the exact location of the triple pole isolator (or indeed if one is present at all - there is no 'switch' present on the wall, I'm not sure what one looks like). All I can see is that the fan has a 3core cable (red, yellow, blue) with no earth going into it, and the bathroom light switch has red and black wires.

    If someone could tell me how to wire in the mirror in relation to the diagram, or point me in the direction of a diagram with heated mirror included, it would be very much appreciated.

    PS I am aware that local authorities have to inspect the work

    PPS The mirror is fitted with an IR switch, does anyone know if this will control both the light and heater?

    Thank you very much!
     
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  3. electronicsuk

    electronicsuk

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    If the mirror is designed to be connected to a lighting circuit and the instructions don't specify any requirement for a fused connection unit, it should be a relatively simple case of taking permanent live, neutral and earth from the main bathroom light. Presumably there will be no need for the mirror to come on with the main lights, as you mention it has a separate remote control.

    Oh, and you must ensure that RCD protection is provided. How you do this is up to you, but it seems that the most sensible way forward would be to move the lighting circuit onto its own RCBO, if your CU will take these.

    EDIT: I presume that as you have read the WIKI, you're aware of the different zones in the bathroom. You'll need to check the instructions for the mirror to see where you're allowed to install it.
     
  4. CanIEat

    CanIEat

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    Indeed the mirror is meant to be connected to the lighting circuit with no indication that an FCU is required.

    I am not really sure about the RCD part... before starting, I was able to isolate the bathroom light, hall light and one bedroom light only (sockets in hall and bedroom still working) by tripping one of the circuit breakers at the CU. So I think these lights are on their own circuit, is this what you mean by providing protection? Is a RCD another type of circuit breaker I might need?

    Thanks for your reply.

    PS on further inspection of the light switch it has 3 red wires going into L1, and one red, one yellow going into COM. The others (3 black, 1 blue) are all grouped together (in one of those little plastic blocks - does that mean they are terminated?). I don't know if this makes a difference, it seems more complicated than the layout shown in the WIKI diagram.
     
  5. electronicsuk

    electronicsuk

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    An RCD is not the same as an MCB, a-la circuit breaker. An RCBO is a combined circuit breaker and RCD, and if your consumer unit is fairly modern then you should be able to replace the MCB for that lighting circuit with an RCBO instead.

    You would take neutral from the terminal block with the blue/black wires, live from the L1 terminal on the switch, and earth from the bare copper green/yellow sheathed wires, which presumably you have?
     
  6. CanIEat

    CanIEat

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    Yes, I have these. But I will be able to take them down from a junction box at the light itself? I thought that's what you meant before. This would be more convienent than taking it from the switch which is located outside the bathroom.

    I'm not sure how to tell an MCB from an RCBO. On the consumer unit, which i suspect to be about 15years old, there is the main on/off switch together with 5 breakers. If it's straight forward enough would you recommend just changing them all for RCBOs? Or is it only necessary in this case as this is a bathroom installation?

    Thanks again.
     
  7. CanIEat

    CanIEat

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    Hi, had another quick question, is it necessary to install a transformer before the mirror? Inside the mirror there is an 'electronic ballast', I'm not sure if this does the same thing?

    Thanks again.
     
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  9. electronicsuk

    electronicsuk

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    It is unlikely, from the sounds of it, that your CU will be able to take an RCBO. It might help if you posted a picture, but it sounds like an old Wylex standard with retrofit MCBs. If this is correct, that leaves the option of a CU upgrade as part of this work, again notifiable, or a seperate RCD somewhere local to the bathroom.

    As you seem to have loop in/out at the switch, there will be no permanent live available at the fitting on the ceiling. You will need to take a feed directly from the switch, unless you can live with the mirror only working when the main light is on.

    Assuming the existing light and mirror are the only electrical items in the bathroom, you could add RCD protection by installing a PowerBreaker RCD fused connection unit outside the bathroom before the light switch. This would allow you to comply with the regs without a CU upgrade.

    Given that this work is notifiable and that you seem to have a lack of some of the basic knowledge required to do the work, I would seriously suggest you call an electrician in. The fees for notification won't be too dissimilar to the cost of an electrician for this small job.
     
  10. ban-all-sheds

    ban-all-sheds

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    I thought Stirlingshire was in Scotland? ;)

    But I agree with the sentiments re an electrician - CIE, you do seem to be floundering and you don't have the right tools. We can point you at information here, but we can't reach through the internet & wire it for you, so if you don't understand you probably shouldn't risk it.

    And asking "is it necessary to install a transformer before the mirror?" (Why? What sort of transformer?) shows that you really don't understand a thing about electrics...
     
  11. CanIEat

    CanIEat

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    Here is a pic of my CU:

    [​IMG][​IMG]

    What do you think then would it take an RCD/RCBO? Otherwise the fused connection unit sounds like a good idea. (The only elctrics in the bathroom are the light, fan, and soon the mirror...)

    Ban-all-sheds, you are correct that I have little knowledge of electrics, that's why I'm on a DIY forum asking for advice. I'm a reasonably intelligent and practical person and having already completed the tiling and plumbing in my new bathroom without prior knowledge in those areas I thought it was reasonable that I might be able to connect 3 wires in a cable up to a ceiling rose. I ask so many questions/"flounder" (the transformer idea was from someone who apparently knows what he is talking about...) because I feel it's better to check as much as I can before doing the job. As far as tools go, is there something I might need which I'm unlikely to already have?

    Electronicsuk that's a good point about there only being a switched live at the light fitting, but there's no window in the bathroom so the light is always on when I'm in there and I can live with the mirror only working with the light on.

    Thanks to you both for all the advice.

    PS At this stage I have cut channels in the plasterboard and ceiling and have some plastic conduit in which to run the cable. Is this correct?
     
  12. electronicsuk

    electronicsuk

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    The MCBs in your CU look like they're manufactured by Merlin Gerin, in which case, an RCBO replacement is very likely to be available. You need to confirm the manufacturer, if it does turn out to be M.G, there are plenty of RCBOs available on ebay here.
     
  13. CanIEat

    CanIEat

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    Job now eventually completed, thanks very much!
     
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