ECN Forum Forums Photo Discussion Forums Photos for General Discussion New apartment services (UK)

Hi Adam and welcome,
Good comment, I'd forgotten that cable tray comes in two types.

At the very least, I would have used some plastic cable clips (the type with the nail in them) to tidy the wires up as they were run into the equipment.
If there's one thing I can't stand the sight of, it's messy cable runs.
Cable ties seem to be the way to go these days, wether the actual cables themselves are held to anything or not.

The orange stuff does look like fire-resistand wiring of some sorts. Here the orange stuff is NHXH E30 or E90 (minutes fire resistant), with an outer sheathing that polymerizes in heat and turns to a ceramic-like substance (but not powder-filled like MICC). Weird idea to use that for an apartment service for sure. Helluva expensive and only used for critical applications here (elevators, safety lighting, sprinkler controls and pump feeders,...)

To cover some of the points raised for those not familiar with U.K. systems, the gray cut-out box mounted on a board with open cables to the meter is quite normal. If this were the service at a regular single-family residence, then it would be quite normal for the output(s) from the meter to be connected directly into the main distribution panel(s) which would be mounted alongside or backing onto the meter cabinet (although sometimes there will be an isolator here if the main panel is some distance away or if it's been added on newer services).

Depending upon the age and style of service, the supply cable will be a lead-sheathed type (if underground), individual insulated conductors (common on overhead supplies), or a concentric neutral cable with PVC outer sheath. It's the orange sheathed cable which makes this installation look odd for a start, as it does seem to suggest that it might be MICC (Mineral Insulated Copper Clad). As noted already, using MICC on these feeders would seem to be overkill if that's indeed what it is.

The fuse carriers on the cut-outs are normally just black or gray to match the rest of the unit. As John noted, the red is used to indicate that they are fitted with solid links rather than fuses, which of course makes sense if the MICC (or whatever they are) feeders are fused at a common supply room.

Just in case there is still any confusion about the three current-carrying conductors emerging from each meter, this is not a 3w 120/240 or 240/480V type system, but simply one line which is permanently live and the second which is controlled by the meter to supply power only during the Economy 7 cheap-rate hours. The detailed photo I've seen of the meter confirms that it is standard E7 set to the normal midnight - 7 a.m. hours and not E10.

Incidentally, this is the whole reason I was sent the photos in the first place, to confirm that the apartment had E7 or E10 service.



Good catch on the little black section visible. I'm not so sure about sleeving being applied for the full length though. It looks too snug and too much like the other phase conductor to be sleeved to me. My guess would be that's just some black tape applied at the end to help identify the off-peak line from the permanent-live during installation.


That's one of the things I don't like about the modern green/yellow earth cable which has just a thin longitudinal green stripe. When the conductor is twisted a certain way, as here, it appears to be just plain yellow. It's no big deal here as its function is obvious anyway, but it's an issue in a crowded junction box which might also have plain yellow phase conductors. If you look at the link from the black junction box to the cutout in these pics you can just about see the green stripe there.

Speaking of the PME connection, have you noticed that the right-hand service has it connected to the neutral in the usual way, on top, while on the left-hand service it's run into the bottom? And why the junction boxes anyway at this point? Why not just run the earths straight to the bonding terminals in the cutouts?

The whole setup seems to have been ill-planned, as evidenced by the fact that one service has the meter installed on the board while the other, clearly short of space between the wall and cable trays, has the meter mounted separately above.

Yes, the grounding conductor is generally attached to the main panel, and will be either green or no insulation.

Thanks for the explanation. It's always interesting to see how things are done outside the US.

Adam,

In the U.S. it's also possible to find a common bus in the main panel to which both neutrals (grounded circuit conductors) and earths (grounding conductors in NEC parlance) are connected. They're kept strictly separate in sub-panels and beyond, as here, with an exception for ranges and dryers which for many years were allowed to have their frames grounded to the neutral.

In the British PME (Protective Multiple Earthing) system, the installation is grounded to the neutral only at that cut-out ahead of the meter. Neutral & earth/ground are kept completely separate from that point on, so main panels have an isolated neutral bus and separate earth/grounding bar.

To return to this specific case, I've had some of my guesses about the building confirmed. It's a 3-story block with two apartments per floor. These pictures are from the U.K. 1st/U.S. 2nd floor, so I think we can assume that the shared meter cupboards are probably built one above the other and the two MICC(?) cables running vertically on the cable tray must therefore be the feeders to the top floor.

What's at ground or basement level to feed these is anybody's guess. A single 3-phase feeder to a PoCo-owned distribution panel with OCPD for each subfeed? Maybe seven individual 1-ph feeders (allowing one for communal services) from the street which have the usual fused cutout?

We're used to seeing all sorts of odd meter locations in old places which have been converted into flats, but on a new build I wonder why it was done like this at all. If there's a common utility room at the bottom, why not just put all the meters and isolators in there, then the SWA subfeeds could have gone directly to each apartment, eliminating the need for a separate meter closet/cupboard on each floor entirely.

The only reason I can think of for wanting the meters near to the apartment they serve would be if some flats were going to be using prepayment card/key meters, or somebody thought there was a chance that they might do so in the future.

I'm just thinking out loud here, of course. It would certainly be interesting to see what's at the common supply point.

I hope those tails are double insulated as single insulated conductors are not permitted to be used for meter tail applications. Also there should have been a fused isolator used for the isolation of the armoured cables as otherwise the suppliers fuse is protecting the whole length of the cable including the SWA to the apartments. The armoured cables glanded into the trunking do look very sloppy also not that because they are glanded into the same metallic enclosure they will now be sharing an earth connection. I susopect there will be some sort of through crimp in the trunking joing the meter tails to the armoured cores, and this is not ideal either.

All in all a very sloppy installation.

Good point. It's safe enough without (assuming the SWA is suitably rated), but rather inconvenient if a fault takes out the PoCo fuse. I would have thought that the utility would have objected to this, but then with the actual supply work and the metering being handled by different companies now, there's probably no coordination to have caught it.



If the plumbing system is all metallic and is properly bonded, there will be parallel paths anyway. I wonder how the earthing has been handled in that trunking and in the apartment? It could be 4-core SWA with the armor not connected at the load end.

By the way, I reckon the load on the E7 circuit must be pretty light. It seems that the apartment does not have storage heaters, but instead has been fitted with the Dimplex pilot-wire controlled panel heaters, so they'll be on the permanent live. Unless there's something else I don't know about, the only appliance on the off-peak supply seems to be the water heater.