Is there a maximum length for a spur cable?

Thanks Andy for the link to the IET article, and to everyone for your comments. I don't disagree with anyone.


If you want to run electricity to a small outbuilding, e.g. a garden shed, then there is no need to go over the top with the installation. At a previous house where I lived, I supplied a single garage by means of a single 2·5 T&E cable feeding a twin socket and a switched, fused spur point to operate the lights. There was a two-pole switch at point of entry to the garage.This, to my mind, met the Regulations at the time. It was very similar to method 2 of the IET article, except that the feed came from a spare way on the main fuse board. This seemed more straightforward than finding a place on the ring circuit into which to break in and install a spur point.


Method 2 is acceptable; method 1 is preferred. It is more robust and future-proof and may be more appropriate if there is a good amount of electrical equipment in the garage, e.g. someone running a small business from there. Of course individual situations vary and various treatments are appropriate. If there is no spare way on the fuse-board, it is a bit of a palava to instal a bigger one just for the sake of a socket in a garden shed.


The area served by sockets means the area within which they are actually installed. An extension lead can be plugged into any socket, whether in the shed or in the house, but this does not mean we need to consider the area of the garden.


Some years ago, at the home of a relative, a bizarre setup was installed. The house was extended and a new double garage was built close by. The electrician installed a new, larger consumer unit in the house, to provide a means to supply the the garage from the consumer unit (no spare way on the existing one). An armoured cable was run underground to the garage, where a small consumer unit was installed. This had three sub-circuits. One was for garage light, a second for garage sockets. The third fed back into the house, through a metre length of conduit at high level, to serve lights in the house extension. The electrician argued that this was more convenient than trying to find somewhere on the existing house lighting circuit to tap into.


As far as I could tell, this did not infringe Regulations, but probably the authors of the Regulations had never envisaged such a cock-eyed arrangement. I was not keen on the house lights being fused in an outbuilding. And if a conduit was used to connect to the garage anyway, what was the point of the armoured cable when this conduit could also have taken the main feed to the garage? In fact this was a case where a single feed to the garage through the conduit to supply the sockets and a fused switched spur point for the light, would have been a simpler, cheaper and satisfactory solution.


Wind forward several years. An electric door mechanism was installed. The technician praised the installation in the garage; it was easy for him to find a good point to connect up to, and the actual workmanship was good. So at least we can say that this bizarre installation was robust and future proof.

Thanks Andy for the link to the IET article, and to everyone for your comments. I don't disagree with anyone.


If you want to run electricity to a small outbuilding, e.g. a garden shed, then there is no need to go over the top with the installation. At a previous house where I lived, I supplied a single garage by means of a single 2·5 T&E cable feeding a twin socket and a switched, fused spur point to operate the lights. There was a two-pole switch at point of entry to the garage.This, to my mind, met the Regulations at the time. It was very similar to method 2 of the IET article, except that the feed came from a spare way on the main fuse board. This seemed more straightforward than finding a place on the ring circuit into which to break in and install a spur point.


Method 2 is acceptable; method 1 is preferred. It is more robust and future-proof and may be more appropriate if there is a good amount of electrical equipment in the garage, e.g. someone running a small business from there. Of course individual situations vary and various treatments are appropriate. If there is no spare way on the fuse-board, it is a bit of a palava to instal a bigger one just for the sake of a socket in a garden shed.


The area served by sockets means the area within which they are actually installed. An extension lead can be plugged into any socket, whether in the shed or in the house, but this does not mean we need to consider the area of the garden.


Some years ago, at the home of a relative, a bizarre setup was installed. The house was extended and a new double garage was built close by. The electrician installed a new, larger consumer unit in the house, to provide a means to supply the the garage from the consumer unit (no spare way on the existing one). An armoured cable was run underground to the garage, where a small consumer unit was installed. This had three sub-circuits. One was for garage light, a second for garage sockets. The third fed back into the house, through a metre length of conduit at high level, to serve lights in the house extension. The electrician argued that this was more convenient than trying to find somewhere on the existing house lighting circuit to tap into.


As far as I could tell, this did not infringe Regulations, but probably the authors of the Regulations had never envisaged such a cock-eyed arrangement. I was not keen on the house lights being fused in an outbuilding. And if a conduit was used to connect to the garage anyway, what was the point of the armoured cable when this conduit could also have taken the main feed to the garage? In fact this was a case where a single feed to the garage through the conduit to supply the sockets and a fused switched spur point for the light, would have been a simpler, cheaper and satisfactory solution.


Wind forward several years. An electric door mechanism was installed. The technician praised the installation in the garage; it was easy for him to find a good point to connect up to, and the actual workmanship was good. So at least we can say that this bizarre installation was robust and future proof.