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

I think that you need to be clear on the type of cable for the distribution circuit. If you can see what's written on it, all well and good, but otherwise, have you had a look in the existing CU?

Chris Pearson: 
 

I think that you need to be clear on the type of cable for the distribution circuit. If you can see what's written on it, all well and good, but otherwise, have you had a look in the existing CU?

It's definitely split-concentric because in the flat, it drops through the ceiling outside the fuse board, then with added insulation tape on the L & N conductors, and G/Y on the combed protective conductors, it enters the board - the speculation was about the 25mm2 csa, as it was just by eyeing up the conductors.

We have just debated unsheathed cables outside enclosures. That certainly does not sound compliant.

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.

I'm sure the DNO will deny any responsibility for anything beyond the end of the meter tails.

If there's a BNO, then the switch fuse and cable belongs to them.  Otherwise, it's the flat owner.

Chris Pearson: 
 

We have just debated unsheathed cables outside enclosures. That certainly does not sound compliant.

No, but it would be within the CU were it replaced. The query though concerns replacing the CU with the cable having room for improvement due to its unknown location, and the owner not wanting the expense of replacement, basically; considering also that the existing arrangement could probably be quite serviceable for years to come without issue. Then there's the concern about the switch fuse protecting the cable.

If there's a BNO, then the switch fuse and cable belongs to them.  Otherwise, it's the flat owner

Agree if it is a BNO, but that is pre-metering,  but here if I have it right the metering is before the sub-main. 

I suspect that few leasehold agreements allow the individual  flat owner to do anything to services in the common areas that belong to the building owner= freeholder, or to any cables passing via other leaseholders rooms.  At best there will be a process of getting a permit from the freeholder, and at worse the free holders may insist on their own contractors and then passing the charges on to the leaseholder.

Usually the leaseholder's property stops at or halfway in to  walls of the flat and at the floor boards and ceiling joists. Now changing a surface mounted cable in the common area is unlikely to be a concern, but anything involving holes or plastering is more complicated and will need free-holder agreement if it is that sort of building. 

(and if you want to see how messy that sometimes gets, just look at the legal fun and games associated with  who owns the cladding on flats now considered unsafe, when the building is leasehold flats bought as units inside a freehold building. The answer seems to be no-one knows, and they all want to pass the cost to someone, anyone, else. )

Mike.

The line conductor is protected by the C.P.C. or Neutral conductors so will cause the fuse to blow if a nail or screw is driven through the cable. Serious building work is unlikely as it may contravene a lease agreement. The cable has done its job for some time so is likely adequate for future use. A consumer unit upgrade in the flat will afford greater safety within the flat. I would not worry too much about the 45 Amp hot wire fuse. If the earthing is good then proceed with a new consumer unit.

Z.

So, with the likes of 132.16 in mind

132.16 doesn't demand that the existing installation is up to current standards, or even adequate in itself, merely ‘adequate for the altered circumstances’. I take that to mean it's provides whatever it need to provide so that your addition or alteration can comply with current regulations and you're not making the existing any worse than it was -  e.g. it has adequate current carrying capacity if you're increasing the load, provides an earthing facility with a low enough Zs, not excessive voltage drop and so on. 

If it really is split-con then while it doesn't meet the letter of the current regs, in practice it's hardly any worse than if SWA had been used - As Z noted - it'll provide ADS just as well, even if it's via N rather than PE.

   - Andy.

A 45 Amp piece of fuse wire made of plain or tinned copper should be of nominal DIAMETER 1.25mm. That is diameter and not cross sectional area.

Z.