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CU Change When Its Distribution Cct Could Be Improved, & DNO Involvement

Farmboy

In a block of two Flats (one on top the other), there’s a 60/80A service head (TN-S supply) by the communal front door. By the head, there’s a meter for the upstairs Flat that supplies a 45A rewireable switch fuse (above the meter), with a (what appears to be a 25mm2) split-concentric distribution cct then running up to the Flat that runs within the fabric of the building [within boxing up from the meter cupboard but then into the walls/floors, with no indication of location, then reappearing in the loft space before dropping into a rewireable fuse box (with just 3 ccts: cooker, sockets, lighting) within the flat]. This setup is duplicated for the downstairs Flat [the Gas (supplying just the upstairs flat) MPB is done at the electricity meter position. The water service pipe, entering by the front door, is plastic, then copper splitting off into two, supplying both Flats, with no evidence of MPB]. No work/testing has been done; this is all just by observation.

The upstairs Flat owner wants the fuse board changed. So, with the likes of 132.16 in mind, can it be changed given the distribution cct could be improved [given e.g., its route is unknown, there’s no additional protection and zones (and a bad idea anyway to have the whole installation on one 30mA device), and it doesn’t have an earthed metallic covering] and the owner doesn’t want any work done on it, re expense and the décor, or would you insist the distr cct be replaced or installed appropriately (e.g. surface mounted or armoured, etc)?

Also, does the DNO need to be consulted re the 45A rewireable switch fuse just after the meter, re the length of tails and ownership? The tails from the meter into the switch fuse are only about 0.5m long, with the split-concentric then running from the switch fuse, but there’s been technical advice that the DNO be consulted to determine whether they are involved in any ownership of the switchgear and distribution cct, but mainly to determine whether the 45A rewireable switch fuse offers sufficient fault current protection for the tails and split-concentric (as far as the owner is concerned, the switch and cable is his) - the suggestion is that 45A fuse has been deliberately kept low to offer such protection, given it’s a 60/80A service fuse. Personally, I think said technical advice is a bit confused somewhere, but they could be correct. So, would you change the CU, leaving the distr. cct alone, and should the DNO be consulted re the switch fuse providing adequate protection?

Thanks

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    Who owns  the common parts of the building  ?- it may not  be the occupant of the upper flat - in which case the best that can be done is to improve the bit inside the flat, so that zone is to the latest regs. 

    The new work is the to current standard, but the part that is in the common areas of the building isn't  likely to be.  Even so it  is still a worthwhile improvement, to update just the bits you are able to get access.  But the comments need to reflect the bits of the installation that have not been updated and why.

    There must be loads of flats where feeds to one flat pass through the rooms of another or run in wall cavities or other non-ideal routes, in the wrong sort of cable and predating safe zones, requirements for RCDs etc. Until these fail, realistically they can not easily be changed, and at that point it may be that a new cable route is used.

    Do sort out the split ends though, even it is just an adaptable box  with henely block or some line taps in it and some stuffing glands.

    Personally I;d not rock the boat about the 45A hot wire fuse unless you are going to change it for an RCBO or a modern fuse.

    Mike.

     

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  • 0

    Who owns  the common parts of the building  ?- it may not  be the occupant of the upper flat - in which case the best that can be done is to improve the bit inside the flat, so that zone is to the latest regs. 

    The new work is the to current standard, but the part that is in the common areas of the building isn't  likely to be.  Even so it  is still a worthwhile improvement, to update just the bits you are able to get access.  But the comments need to reflect the bits of the installation that have not been updated and why.

    There must be loads of flats where feeds to one flat pass through the rooms of another or run in wall cavities or other non-ideal routes, in the wrong sort of cable and predating safe zones, requirements for RCDs etc. Until these fail, realistically they can not easily be changed, and at that point it may be that a new cable route is used.

    Do sort out the split ends though, even it is just an adaptable box  with henely block or some line taps in it and some stuffing glands.

    Personally I;d not rock the boat about the 45A hot wire fuse unless you are going to change it for an RCBO or a modern fuse.

    Mike.

     

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