I've moved into a house, and am fitting a series of 5 halogen downlights beneath a shelving unit. The wall on which I am fitting it previously had an uplighter. I removed this so now have exposed live, neutral and (unsheathed) earth wires on the wall. This is already operated by a light switch on another wall.

The new lights I have come with a fitted fused (3 amp) plug. The instructions say if it is installed directly on a lighting circuit it will need a 5 amp fuse.

So - if I want to wire it directly, can I assume the lighting circuit is adequately protected since it already had a light fixture (is this standard?), or for this fitting do I need to install an (unswitched) fused spur or something similar to add the 5 amp protection?

To clarify, the 5 halogen lights are wired into one fitting with a transformer leading to one plug.

  • From the OP's profile, the location appears to be the UK. Commented Aug 29, 2012 at 8:54
  • @Tester101 outside of a plug? In a spur then? Here's the product link (this might not be the exact model). Its instructions were a bit brief and I want to be sure.
    – waj
    Commented Aug 29, 2012 at 11:40
  • Not exactly. The plug itself is fused with 3A, which is then connected to the primary of the transformer. I want to remove the plug. Would these lights require a fuse when the previous did not, or is this just a precaution?
    – waj
    Commented Aug 29, 2012 at 12:52
  • @Tester101 thanks. So I can assume the lighting circuit isn't itself fused, that this is conventional and that the previous light was deliberately unfused?
    – waj
    Commented Aug 29, 2012 at 14:36
  • @Tester101 Ah I think you have answered my question. Many thanks.
    – waj
    Commented Aug 29, 2012 at 15:46

1 Answer 1


Comments converted to answer.

If the manufacturer says they need a fuse, then I'd probably install a fuse. Just install a 5A fuse before the transformer, and make sure it's accessible in some way.

The light circuit is probably on a fuse/breaker at the service panel, but since you are using a transformer to step down to low voltage a fuse may be required to protect the transformer and low voltage wiring. The fuse/breaker in the main panel will probably be 15-20A; since it's designed to protect a normal line voltage lighting circuit, so you'll need another 5A fuse before the step down transformer to protect the transformer and everything downstream from it.

  • I will attach a 5 amp fuse, thanks @Tester101
    – waj
    Commented Aug 29, 2012 at 16:33
  • @Tester101, what's the proper fuse holder to use in this situation? And does it go inside a junction box? Commented Aug 29, 2012 at 18:18
  • @ArgentoSapiens Not sure, I'd have to do some research on that. Typically there would be parts supplied with the equipment, if this was a typical/valid installation method.
    – Tester101
    Commented Aug 29, 2012 at 19:26
  • @ArgentoSapiens I intend to use a fused spur (or FCU) and place it below my shelving unit. That way I have access to a plate with the fuse in case anything goes awry. They seem to generally be available with a 13A limit, which is more than enough for my needs.
    – waj
    Commented Aug 30, 2012 at 9:08
  • @waj: A fused connection unit (FCU) is probably appropriate but, to protect the wire to the transformer you should fit the FCU with a 3 (three) amp fuse (e.g. use the one from the plug you remove). The wire is sized for 3A but the lighting circuit can provide more than that, enough to start a fire in the wire to the transformer in the event of a fault. Commented Jul 28, 2016 at 9:19

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