Incoming mains board in own flat in London worthy of antiques roadshow!

[Osborn]

Hello all. Never seen a cable service head like the one in the flat I've just moved into (AEI - from the 1960s?). It's 3 phase (60amp fuses), but only feeds two flats (mine and the guy downstairs). Have cleaned the filthy contacts on the live cable head fuse for my flat, and also cleaned contacts in the meter, and in the isolator switch it leads to (MEM and even older than the cable head, by the look of it)... Yes I know I should be getting EDF (supply co.) to do all this, and I could be fined a grand for breaking their seals, but the chances of either of those things happening are - erm - remote. Question is this. I want to upgrade the input and output 16mm meter tails to 25mm. Pulling the live fuse in the cable head - no problem - already done it several times - but are there issues with disconnecting and replacing the existing cable to the common neutral in the cable head? Would only be disconnecting/reconnecting the neutral for my flat at the cablehead common neutral - I'm not touching any of the wiring for the downstairs flat. All wisdom welcome. Many thanks from a newbie…

 

[High Tower]

wouldnt touch it in a month of sundays!

Not your equipment, but is your liability, especially in a flat with other tennants in the area

 

[Osborn]

Thanks. Well, I own the upstairs flat (if not the incoming mains board equipment in the hall). And the only other person using the I/C supply is the other owner - of the downstairs flat (and he knows that I am planning to do some work on the I/C supply and is happy with that....) Here's a pic of the open cable head, with above it, the two MEM switchboxes (meter is out of the pic on the left). My live fuse is the (slightly skewed) one in the chamber third from the left ... Is anyone familiar with this kind of cable head? My specific worry is this: if I replace my circuitry with new 25mm cables , that obviously means disconnecting my existing neutral cable from the common neutral point - in the chamber on the far right. I'm not planning to touch any of the circuitry for the downstairs flat. Is it possible that, after I pull my live fuse, and disconnect my neutral from the common neutral - the downstairs flat will get a lot more than 240v?

 

[High Tower]

Cut out looks fine, if you want it replacing phone the DNO and complain of dripping tar and a burning smell.

If your having problems with under voltage then I would suggest that the tails to and from the switch fuse are woefully undersized it may just be the pic but they look like they are only 6/10 mm2

 

[Osborn]

Thanks again for the quick reposnse HT. Sorry for photo not being exactly hi-res! Probably me being thick, but by "switch fuse", do you mean the fuse on the live in the cable head? Cable leading from it (to meter) is definitely 16mm2, can't be certain about cable end emerging from the tar to the bottom of fuse holder - probably 10mm2. No problem with under voltage in my flat, it often rises to 250, and never, as far as I'm able to tell, goes below 240.

The reason I'm reluctant to involve the DNO and the possibility of replacing the cable head is, I don't want to cause any disruption of supply to the owner of the downstairs flat. He's happy with things as they are at the moment (i.e is reluctant to share the cost of any electrical work done to the i/c supply). Any idea what the DNO might charge for modernising the kit?

 

[High Tower]

the switch fuses are the two boxes above the trunking, the red and black cables in those do not look like 16mm but having said that, it could just be the picture.

You are commiting a offence by tampering or working on the DNO's equipment, your not even supposed to have the cover off the cutout!

They are the only ones that can carry out such work.

The tolerances for voltage requirements in the uk are 230v +10%-6%

so between

216v and 253v

If your supply is within these parameters then it is ok. can i suggest you might want to leave the equipment alone and employ the age old addage of "if it aint broke leave it the feck alone" as you could either get yourslf prosecuted or killed (or a combination of the above)

I assume that you are not a electrician as you were unable to identify the switch fuses in your picture so just to clarify that what you have already carried out is well beyond the remit of even the most capable of DIY'ers so with the greatest respect i suggest you leave your supply alon from here on!

 

[Osborn]

Fair enough HT. Respect your advice - and thanks for your interest.

 

[mogga]

as HT says DONT Touch specialy given the age of the head Id be concerened about anything cracking ,crumbling and the fuse carriers on this cable head ( if memory serves me right) arent completly shrouded like series 7 but leave top of fuse open till fuse is nearly all the way in IF you are concerened in any way about the condition of cable head PHONE DNO rather than risk injury to yourself and damage to your property
Personaly Im wondering WHY did you feel the need to investigate cable head lubrication cleaning contacts ect

 

[High Tower]

Fair enough HT. Respect your advice - and thanks for your interest.

please dont think i was being damming or disrespectfull of your abilities. the DNO's take a dim enough light on us as sparks removing cut out covers, letalone yourself.

Only concern i would have is your earthing arrangements, is it TT through a rod or is it TNS through that pish flimsy unsheathed cable bonded to the trunking?

 

[Osborn]

Apologies HT - realise my short response above might have looked a bit disgruntled. I do understand that your advice - and mogga's - is motivated by concern rather than anything else.

A bit of history: when the supply co guys came to read the meter a few weeks ago, I asked them about my wish to clean the contacts in the cable head and check all the circuitry leading from it to the switch fuses. Their response, to my surprise, was simply 'get in an electrician to do it'. One of their electricians, I asked. No, they said, any qualified electrician! As you correctly identified, I am not one of those, but have done a fair bit of DIY spark work in the past. I'm aware of the simple and obvious dangers. But this shared cable head is brand new territory for me. Hence the original post/query. ....So, as any electrician is going to have to break the seals on the cable head and meter to investigate, I decided to have a look myself. Cleaning the contacts has already brought a noticeable improvement to the audio and video in my flat, and I was wondering whether replacing the old 16mm2 cables with 25mm2 from the cable head to the meter, and from the meter to the switch fuses, would bring a further improvement. That's my motivation. Explain to the supply company that you fear you are not getting the best results from your audio because of their ancient i/c supply, and they will surely yawn, or laugh out loud. On the other hand, dripping tar and smells, as you say, might arouse their interest. I simply want the hardware that's there - it's old, but to my way of thinking, sound - to work optimally. And new input and output tails can't be a bad thing can they?

 

[High Tower]

Smell of burning, molten tar, buzzing noise from the cut out, all of the above will bring concern to the DNO's

My main concern is really your earthing arrangemnents as there does not seem to be any substantial supplied earth present, if thats the case then that poses clear and present danger

 

[malcolmsanford]

Not being a killjoy here but do you envisage the need for a 100amp supply to your 1st flooor flat as that is quite a large load. I would be interested in seeing if you would actually gert a 25mm in that neutral connector block.

In all fairness though your on a common neutral bar with the other flat your neutral is in a seperate way, you will though have to be careful and ensure that the correct neutral is isolated and you may even have to isolate both installatiions as there very well could be a load on that bar coming back through your neighbours installation if it was under load.

 

[High Tower]

I dont think the tails are 16's i think they are 6 or 10's as they look to be exactly the same size as the cables leaving the load side of the switch fuse, and they look to be T&E so im guessing they probably are not 16mm T&E, so assuming im right and they are 6/10mm then the tails look to be about the same size.

As i said i could be wrong, i often am!

 

[nikmet]

Im amazed by all of this!! leave this work to a professional electrician, cant believe what i've been reading, are you thinking about taking the gas meter apart next?, make sure you inform your neighbour so he can keep a safe distance :-O

 

[Osborn]

Re the earth, yes, assumed that all those metal (iron) connections with screwthreads, nuts and bolts would be poor connectors when compared with an unbroken length of 10mm2 copper conductor. So, seeking a more effective, lower impedance earth, have connected a new 10mm2 earth cable from the earth of the T&E at the top of the switch fuse to a new earth block - and connected that to the two bonds (!) the incoming mains cable - one standard 'wrap around' bond a few feet down the cable - and nearer the cable head - what looks like a PME connection.

Thinking a little more about this - and thanks for all the contributions guys - the one cable I can't get at, so I'm stuck with (can't replace) is the 16mmm2 T&E from the switch fuse to the CU (one floor above). So perhaps it's better to stay with 16mm2 all the way from the cable head. Until the switch fuse, it's all single core 16mm2, some of it without double insulation, so on the photo it looks narrower! The exposed cable ends (in the cable head and meter and switch fuse boxes) are dirty and damaged - so it's probably best replaced.

 

[Jonesy83]

ill give you some advice mate
leave it alone

 

[Engineer54]

I agree with nikmet, and others here, you have gone way past your competance and understanding, and are now into the realms of being outright dangerous to yourself and others. Leave what you clearly DO NOT Understand to those that DO!!

I hope that others here offer you no more assistance of any kind, apart from telling to STOP!!

 

[High Tower]

Re the earth, yes, assumed that all those metal (iron) connections with screwthreads, nuts and bolts would be poor connectors when compared with an unbroken length of 10mm2 copper conductor. So, seeking a more effective, lower impedance earth, have connected a new 10mm2 earth cable from the earth of the T&E at the top of the switch fuse to a new earth block - and connected that to the two bonds (!) the incoming mains cable - one standard 'wrap around' bond a few feet down the cable - and nearer the cable head - what looks like a PME connection.

Thinking a little more about this - and thanks for all the contributions guys - the one cable I can't get at, so I'm stuck with (can't replace) is the 16mmm2 T&E from the switch fuse to the CU (one floor above). So perhaps it's better to stay with 16mm2 all the way from the cable head. Until the switch fuse, it's all single core 16mm2, some of it without double insulation, so on the photo it looks narrower! The exposed cable ends (in the cable head and meter and switch fuse boxes) are dirty and damaged - so it's probably best replaced.

When you say you have bonded your cable, I assume when you say wrap round bond I'm hoping you havnt put a earth clamp on, if it says BS951 on the clamp then get it off before you irepribally damage the supply cable which will be your liability

 

[Spudnik]

And with that in mind, and the strong recommendation from the above members, please get in touch with your local DNO.

This is not something that even an electrician can touch.

Good luck and let us know what they say.