I have a 30s house with some rubber-coated wiring. Before replacing this, I'm going to put in a new consumer unit. Before doing that, I'd like to ask a couple of questions.
My problem: There is no consumer fuse - tails go straight from the supply cable to the meter. From the meter, the tails go to a small junction box (would this be a "Henley" block?). Tails then go from the junction box to the consumer unit. My plan is to carefully remove the old consumer unit tails from the live terminals using an insulated screwdriver, then fit new consumer unit and new tails.
My other problem: The current wiring would not pass any sort of inspection, and I'm not expecting to finish the rewiring very soon.
Q1: Who owns the junction box? It is after the meter, but is sealed with wire and (old looking) lead crimps. That might mean something official, or might be to discourage me from the above dangerous manouver.
Q2: What exactly is inside the junction box? Bakelite box, about 4" x 3". The meter tails enter on the bottom-right one in front of the other (ie in a plane perpendicular to the wall) and the consumer unit tails exit on the bottom-left, similarly one in front of the other.
I'd doubt that it doesn't have a fuse, what's on the end of the incoming cable? Our 1930s place had a metal "head" on the end of the cable, the fuse was in there - although it didn't look like it... LEB (as was) was quite happy to change it to a modern plastic cutout+fuse FOC.
At least removing the tails from the junction box is considerably safer than trying to do it with live tails from the meter ;)
Your procedure sounds high risk to me. There should be a fuse on the incoming, maybe you haven't found it yet. I'd ring your elec supply company and ask them to fit one pronto if there isn't. The only downside of this is they may well condemn your wiring if they see it.
AFAIK the junc box after the meter is yours to do with what you like. What the elec companys do care about is any tampering with the meter seals. They don't seem to care if you remove those on the fuse before it.
Eeeeeeek! You (or I) *really* don't want to be doing that. "Live working" is something to train for carefully, needing planning ("what if the wire springs back, what will it touch") and well-tested tools and kit (VDE-rated insulation, thick insulating mat). It's a *really**really* poor idea to improvise. Even more so on an installation you're already saying is (to use a technical term of art) crap.
Rather than a "big bang" changeover, many competent d-i-y'ers do the "new CU" thing by running brand new wiring to a nice shiney new CU alongside the old one, and feed the new CU's incomer from a suitable way in the old one (30A or 40A rated) - diversity-for-real is your friend here - to allow new and old circuits to both run during the week or five it takes to do the job in evenings/weekends, while having power for joist-drilling and the like!
But if you really have 60-yr-old rubber-covered cable, you're likely to find it breaking off the cable as soon as you wiggle it even a bit. Are you sure you can't scrape up the cash to do something safer - maybe run new circuits for one or two "essential" power rings and lighting, wired in to a lots-of-room-for-future-circuits new CU, then get a friendly local electrician to connect it up (and cast an eye over your earthing arrangements), leaving you to put in further circuits at your leisure? I'd really not want to be living in, or responsible for, a house with the wiring in the state you suggest...
It's really quite massively unlikely that you don't have a supply fuse (conceivable, yes, but barely so); perhaps this Junction Box is indeed a supply fuse and neutral link? How deep (front-to-back) is this mysterious Box? Have you looked for a supply fuse further back from the supply cable? (At this age I'd expect the supply cable to be a tar-impregnated lead-sheathed thing: are you saying the inner conductors emerge from that directly into the meter?) Maybe there's a supply fuse further back, possibly at a previous meter location?
I've guessed at it being a supply fuse, incorrectly positioned beyond the meter; but it sounds a bit small for that - and even in the 30s few sparkies would muddle them up this way - so it could indeed be an old Henley block (maybe put in when replacing a bunch of ancient-style fuseswitches with whatever CU-substitute you now have... but haven't had a chance to describe...)
Let me discourage you again from trying to keep this installation struggling on: better to put up with a pain in the cash flow and running with fewer, but safe, circuits for a while, than disturb the old perished stuff which (from personal experience) starts to flake off most worryingly when disturbed.
I'd second everything that Stefek has said. *If* you have old PBJ (poly butyl jute) Lead-Ins and no main fuse, contact your local distribution company and tell them what you think the arrangement is. They are required by statute to have a suitable means of fusing to protect your property in the event of a fault in the meter or the tails to and from the meter. Make sure you tell them that in your opinion you think their installation is unsafe and needs inspecting as soon as possible. They will also replace the lead in cables at their expense if they don't meet modern safety requirements.
The only catch with this is that they also have a mandate not to connect a supply to a system they consider unsafe, which yours almost certainly is. One way of dealing with this is as follows:
(1) Install nice new consumer unit alongside. (2) Install one 13A socket from the new consumer unit. (3) Ask your supplier to come and make their supply safe, connecting up to the new consumer unit.
They should now come and replace the dodgy setup, and will probably upgrade the meter to a nice small one at the same time. Depending on the electricity board they might even fit a 100A isolator between the meter and the new consumer unit. They will test your circuit to see if it is safe (should be OK with only one 13A socket!), and off they go.
Now, you can run the old fusebox off a 40A circuit in the new one (the other way round to what Stefek said). This way all new circuits can come off the new CU as you fit them, and eventually you just remove the old fuse box.
HTH, Al
PS The 13A socket idea isn't mine - I read it on here a while ago.
It may have changed, but the wording was something like 'where they are prima facie satisfied that a danger to the public exists'. Unless things have changed significantly in the last 7 or 8 years, no leccy company will be too anxious to disconnect a supply unless it really is dangerous, and not just old.
I thought the OP said he was going to remove the tails from the Henley block, surely the tail won't actually be live once it's removed from the block will it? Or am I missing something obvious?
Agree with the point about the rest of the installation though, probably best not to actually attempt to connect any of it back up... ;)
No, but... assuming it's a Henley block, he's still got to do honest-to-goodness Live Working to get his tails *out* of the Henley Block (or whatever it turns out to be), working with the thing open, giving the securing screws *plenty* of heft (we hope they've been done up tighter than the proverbial aqautic bird's back passage, right?), all in an environment of known crapness and uncertain vintage. And then another bout of Live Working when putting the new tails back into the aging Henley-or-whatever. And there's allegedly no supplier fuse on this incoming feed; so if there's a short on the new installation (we haven't heard the poster make reassuring noises about taking a trusty low-ohms multimeter to the new final circuits, have we?), the opportunity for flying shards of damn hot copper and *severe* embarassment seems excessive.
Keen as I am on competent d-i-y'ing unencumbered by trade-body-monopoly stuff, I do view Live Working as firmly on the *wrong* side of the have-a-go line, and definitely in the category of "if you have to ask, you don't have the knowledge to be safe". Asking is good, as it helps to turn a vague "I wonder if I could get away with..." into a firm and better-motivated "bloomineckerslike, off to Stores for another of those Poles, Barge, Wooden, Full-length, Touching, For The Avoidance Of" implements.
... is clearly a bog-standard 2-pole Henley block. In the past (pre the coming of the consumer unit concept) they were often provided by the supply co. in order to connect additional fuseboxes and were routinely sealed, being part of the suppliers' works.
Just what I was thinking. The main fuse(s) must be there somewhere and my guess is that it will turn out to be a pre-1937 cut-out with a fused neutral. Sometimes these had really tiny fuses in - 15A or so!
If this is the case the cut-out, and just about everything else on the supplier's side is likely to be seriously undersized - so any hope of just connecting in to the block sounds a bit optimistic. The correct procedure (AIUI & IME) is to consult with the supplier (the supply network operator) regarding the need for upgrading of their side [1], then complete your new installation - which must include inspection and testing and completion of an electrical installation certificate to BS 7671. You can then call them out to do their side and connect your new tails at the same time. Now that the ESQC regulations are in force you won't get connected without the certificate; the days when 'the board' would do the testing for you are long since gone. But YMMV; it can depend on who you get.
[1] This is a good time to consider earthing arrangements, and check what will be offered. If the service cable has to be replaced you'll almost certainly be offered PME (TN-C-S) so you can base your new design on Ze =
0.35 ohm. If an older cable is retained then TN-S conditions may obtain, with Ze = 0.8 ohm.
DIY could turn into DOA if you've to make changes to a live mains supply. A supply without a consumer fuse is a definite "get in touch with the supplier" scenario to me. I too, like Stefek, would get a big long barge pole.
Not necessarily - under the supply regs they`re not obliged to provide an earth, and cutouts are usually replaced "like for like" without altering existing earthing arrangements.
In our area, providing an earth is now a chargeable job.
I think also you may be expecting a more 'sophisticated' situation than there is in reality. When our supply was undergrounded a couple of years ago the chap who actually made the connection said to me 'would you like an earth terminal?' to which I said yes without really thinking.
Since the existing installation was TT and, on inspection, the 'earth terminal' was a TN-C-S (PME) one I have actually not used it as I know that our earth bonding isn't up to the standards required by a PME supply.
The undergrounding was done very well by the way and the installers (24/7) were very helpful to me, they dug an extra trench to allow the meter to be moved into the garage (from being a box on a pole outside) and left me some bits and pieces to finish off my bit of underground cable to the house.
What was missing was a proper interface to 'the electricity company' which of course no longer really exists.
Thanks to everybody for all the responses so far - I'm going to go through them carefully and have a rethink. Actually, just buying the insulated screwdrivers started me rethinking rather seriously.
Of course I was wrong: the electricity company fuse(s) will be in the green metal box at the top of the supply cable as Lee suggested. I was confused by the installation in my previous 30s house which had a separate in-line fuse in the live tail.
I have already moved the rubber cables (they didn't crumble) to a new CU running off a 30A fuse in the old one. My rethink is to leave both CUs in place until the end of the job, replace the cables to the new CU, and then finally replace the original CU with a split CU for all circuits - and probably get the electricity company to sort out their bit while they cable me up (ie it won't be ME with the insulated screwdriver).
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.