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Long meter tail upgrade, no nice solution comes to mind.

Russell Edwards

Hi All.

Thought I'd open this one up for discussion as I'm sure some of you can come up with a nice solution.

I've been given a friendly notice that i need to do something about the meter tails in my house by my DNO following the installation of a smart meter. They're the wrong gauge for the master fuse (16mm2 on a 100A fuse) and too long, about 4m. I'm having a job coming up with a solution I like. The current installation is original from when my house was built in 1996 and has gone unnoticed until now.

The meter is in a box on the front wall of the house and the tails exit this, run up the inside of the wall and over the ceiling of what was originally a bin cupboard in an uninsulated roof space before entering the distribution board directly though the hallway wall. The logical thing to do would be to protect the tails by replacing them with SWA but I have two problems with that. 1 that I have no way of terminating the SWA in the meter box without invading the DNO's space and 2 I'm not confident in brining in SWA from behind the board, as I'd effectively have to terminate it long and push some excess back into the roof space, and end up with the SWA termination in the wall screwed to the back of the board. So I can see this option needing me to bring the SWA in from above or below the board which would be ugly as sin in my hallway, doubly so as it'll have a bend radius easily measured in miles.

So I've considered using Steel Conduit instead, as that should be as tough as SWA. However unless I've missed something the largest I can get is 32mm OD which has an ID of circa 27mm. As I'm expecting some quite high temperatures in the roof space during the summer 25mm2 (rated to 101A if I'm reading Appendix 4 properly) could well end up under rated in the summer, so I'd be best to use 35mm2. This has a max OD of 13.5mm according to Doncaster cables meaning it'll be tight getting 2 down it.

I considered using XLPE Insulated 25mm as that can run hotter but of cause there's the 70 degC conductor limit of the board so it's not a help.

Bringing my back to SWA again.

I don't want to put joints in above the bin cupboard as there's no way of inspecting them.

So any other ideas of what I could do to protect the cables sufficiently to ignore the limits?

Thanks in advance.

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  • Russell Edwards said:
    I considered using XLPE Insulated 25mm as that can run hotter but of cause there's the 70 degC conductor limit of the board so it's not a help.

    Well it is if the 70 deg limit is exceeded only in part of the route.

    It has been an interesting discussion, but I think that if it were my home, I'd join some 25 mm² cable to the existing 16 mm² and pull the lot through. (I appreciate that the anticipated loads might rule out 16 mm² cable.)

    The 4 m length does not particularly bother me. As I have said previously, is the problem the first meter or the last, or indeed part of the middle?

    This discussion has become far too complicated.

Reply
  • Russell Edwards said:
    I considered using XLPE Insulated 25mm as that can run hotter but of cause there's the 70 degC conductor limit of the board so it's not a help.

    Well it is if the 70 deg limit is exceeded only in part of the route.

    It has been an interesting discussion, but I think that if it were my home, I'd join some 25 mm² cable to the existing 16 mm² and pull the lot through. (I appreciate that the anticipated loads might rule out 16 mm² cable.)

    The 4 m length does not particularly bother me. As I have said previously, is the problem the first meter or the last, or indeed part of the middle?

    This discussion has become far too complicated.

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