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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.

Parents

  • I can vouch DNO's want to know if you're fitting them to a property with a 60A main fuse.

    I've a feeling they want to know even if you had a 100A fuse - as the increase in demand adds to the transformer load and the demand on the street mains.

    1 that I have no way of terminating the SWA in the meter box without invading the DNO's space

    Official answer to that is to install a separate enclosure next to the meter box - ordinary & slimline meter boxes are readily available. That gives you plenty of room for termination and a switchfuse (and exposed tails before the switchfuse for any current clamps).

    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,

    Can t be re-routed so be straight up/down where visible and then covered using maxi trunking? Or re-position the CU?

    - Andy.

Reply

  • I can vouch DNO's want to know if you're fitting them to a property with a 60A main fuse.

    I've a feeling they want to know even if you had a 100A fuse - as the increase in demand adds to the transformer load and the demand on the street mains.

    1 that I have no way of terminating the SWA in the meter box without invading the DNO's space

    Official answer to that is to install a separate enclosure next to the meter box - ordinary & slimline meter boxes are readily available. That gives you plenty of room for termination and a switchfuse (and exposed tails before the switchfuse for any current clamps).

    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,

    Can t be re-routed so be straight up/down where visible and then covered using maxi trunking? Or re-position the CU?

    - Andy.

Children
  • in reply to AJJewsbury

    Thanks Andy

    1: Absolutely agree that DNOs and to know in every case. there's an ENA form for that exact purpose, but the route through the form is different if you've got a 60A master fuse and the EV point has to be limited to no more than 30% of the maximum demand.

    2 Yes I could add another box on the front of my house to house all of this but would you want to do so to yours? I suppose I could loose it on the inside of the wall where the meter box is located but the bin store has been lined with SuperLux (i suspect because the tails ran through it) and is thus not exactly structural. It's quite hard to explain and I realise I'm throwing back curve balls to every suggestion thus for so sorry. 

    3 Yes I could bring it in from above or below but as I've said the SWA will enter the room via the wall the board is mounted to and thus it'll need to bend through 90 deg. As it'll likely be 25 - 30mm in diameter it'll have a bend radius of 150 - 200m would you really want a large black cable poking that far out from the wall just inside your front door? Hence the only option I really see is to enter from the rear of the enclosure and loose the termination in the wall itself.

    Relocating the board has to remain an option, and as it's been washed a couple of times by a leaking hot water tank I'm not too precious about the hall ceiling but it does feel A bit extreme at this point.

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