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loft light and shaver light on one fused spur??

Discussion in 'Electrics UK' started by bruceiow, 12 Sep 2018.

  1. bruceiow

    bruceiow

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    Hi all,

    I have just moved in to a property and am a little confused with some wiring that I have found. So there is a 20amp circuit on the box labelled "Water heater". Turning it off shows that the fridge in the utility room goes off, one socket in the smallest bedroom, the loft light and the shaver light/socket in the bathroom. Confused much.

    So I went to the loft and found a wire coming in that goes in to a wall mount box with a fused front plate. coming out of that box is one 1.5 TAE to the shaver light down in the bathroom, and also a 1.5 TAE to the loft light via a switch in the loft - that drives two normal bare bulbs.

    Now everything seems to work but I have never seen this kind of arrangement. I assume the circuit has been used as an easy way to add things away from the main rings.

    What concerns me is the two things running off the one connection in the loft. Is that dangerous/fire risk territory?? If so I will probably lose the loft light off of it.

    I hate moving in to someone else's lazy DIY jobs haha.
     
    Last edited: 12 Sep 2018
  2. JohnW2

    JohnW2

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    Provided they are all connected to the 'load' side of the fused connection unit [FCU] (i.e downstream of the fuse), you can have as many things connected to it as you want. If those two lights are all that it is supplying, then a 3A fuse in the FCU would be appropriate.

    Kind Regards, John
     
  3. winston1

    winston1

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    If they are "bare bulbs', i.e. incandescent types I would use a 5 amp fuse, as a 3 amp will be taken out when a bulb fails leaving the loft in darkness.
     
  4. bruceiow

    bruceiow

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    cheers guys much appreciated
     
  5. JohnW2

    JohnW2

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    If the loft light fails, the loft will be in darkness regardless of whether or not a fuse blows - and it would be an incredibly unlikely co-incidence IF someone were in the loft AND IF someone else were using the shaver light at the same time AND IF that shave light bulb blew AND IF that bulb dying took out the fuse (of whatever rating).

    In any event, even if that incredibly unlikely scenario were ever to arise, the difference in probabilities of a 3A fuse blowing and a 5A fuse blowing (if either) would, I imagine, be very small.

    Kind Regards, John
     
  6. winston1

    winston1

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    "via a switch in the loft - that drives two normal bare bulbs."

    Are you suggesting both bulbs would fail together?

    I have found when I used to use incandescents that a 3 amp would blow (leaving the internal fuse in the bulb intact) whereas a 5 amp would not blow (but the internal fuse in the bulb blew).
     
  7. JohnW2

    JohnW2

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    You've said that before, and I can't argue with your experience, but it's very different from mine. For decades, I had countless table lamps, standard lamps, bedside lamps etc. with incandescent bulbs and ≤3A fuses in their plugs. and I have no recollection of those fuses blowing when bulbs died. It was B6 MCBs that were the problem (at least for me) in this respect. Also, as I said, in view of the very high transient currents that can flow during death of an incandescent bulb, I suspect it would be pretty unusual to have a situation in which a 3A fuse blew but a 5A one wouldn't have blown.

    Kind Regards, John
     
  8. AndyPRK

    AndyPRK

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    Removed
     
  9. Astra99

    Astra99

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    The OP states there is a 20A MCB marked "Water Heater". This is likely to be a radial wired in 2.5mm², which has been "hijacked" to supply power to the utility room, an additional socket in one of the bedrooms, and through an FCU to the shaver socket and loft lights, all wired in 1.5mm². As it is a 20A radial, I would suggest that this arrangement is perfectly OK regulations-wise, provided the FCU contains a fuse suitable to protect the 1.5mm² cable (13A or lower). I would, however, suggest replacing the incandescent lamps with LEDs. How often have you gone up into the loft to find the light has been left on since your last visit?
     
  10. JohnW2

    JohnW2

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    Indeed. In fact, if the 1.5mm cable is installed Method C, it would be adequately protected by the 20A MCB, so that (at least, as far as cable protection is concerned) doesn't actually need ''fusing down' in an FCU at all.
    Not often, but more than once - but not for several years, since all my loft light installations now have a small light on the ceiling below, near the hatch!

    Kind Regards, John
     
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