DNO isolator fitment - catch-22

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Hello forum!

I am going to be installing a new CU for a neighbour, to replace the old wooden-backed Wylex she currently has. (Small one-bed flat, wired in metric PVC T&E, and the IR for the whole lot is fine)

The meter board is next to the front door, in a small cupboard, only about as wide as the old Wylex. This can't be extended, so the new CU will go on the adjacent wall, with the tails and cables in a bit of trunking.

I want the DNO to install an isolator in the meter cupboard, but there's no room for it until the old Wylex is out of the way. I can't remove the old Wylex until the supply is isolated.
The DNO fuse is (I imagine) in the main TP head down in the stairwell, which is sealed and looks fragile enough for me to not even consider.... The concentric to the flat is terminated in to Henley-esque blocks, then direct to the meter.

So, will the DNO bloke be happy waiting for me to rip out the Wylex after he's isolated before he fits the DP isolator?
Should I make the DNO aware of this or just request an isolator?
Does the householder have to instigate this, as she is the account holder?
Any idea of what they charge for an isolator up here?

The other option is to request a de-energising, rip out everything, then leave my new tails ready for Mr DNO to connect to the meter (or isolator if installed) upon re-energising.

Thoughts or advice? :?:

Cheers.
 
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Request a de-energise in the morning and a return later that day for re-energising. All you usually need to provide is either an isolator or a switchfuse depending on length of tails to CU.

Arrange a generator or temporary access to supply in another flat for power tools and kettle.

However if the head is a bit shonky then it and all the flat mains may be up for replacement.
 
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I work for the DNO (southern electric), and we aren't allowed to connect tails from a CU to the meter/isolator on the customers side. If it's a service fault or a situation where we've taken the supply off and need to re-energise an existing installation, then we can do it.
 
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I work for the DNO (southern electric), and we aren't allowed to connect tails from a CU to the meter/isolator on the customers side. If it's a service fault or a situation where we've taken the supply off and need to re-energise an existing installation, then we can do it.

I don't think that's what the OP is asking for.
 
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Right-oh, thanks for the replies.

What I was assuming was that the DNO would leave me with an isolator all connected up on their side, ready for me to connect my new tails to at my leisure.
But are you saying that I must connect my own tails directly to the consumer's side of the meter (they'll be less than 2ft, btw), then request the re-energise?

Guitar guy, how much is normal for a de/re-energise?
 
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Is this a regular tenement? Nearly every one in Glasgow has the 3-phase 100A incomers you mention in the bottom of the close (mostly still cast iron) which knock out 2 or 3 flats each but they also have 60A cut-out fuses for each flat on the same level as the flat, high up on the wall in a box which is fed by the steel conduit coming from the main incomers in the close. There is one box with 2 or 3 60A fuses for each flat on that level in the close. MICC or tails in 15mm steel pipe then branch off to each flat.
 
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Is this a regular tenement? Nearly every one in Glasgow has the 3-phase 100A incomers you mention in the bottom of the close (mostly still cast iron) which knock out 2 or 3 flats each but they also have 60A cut-out fuses for each flat on the same level as the flat, high up on the wall in a box which is fed by the steel conduit coming from the main incomers in the close. There is one box with 2 or 3 60A fuses for each flat on that level in the close. MICC or tails in 15mm steel pipe then branch off to each flat.

Yeah, it's a regular tenement.

My tenement is about half a mile away, and we did have a cutout OUTSIDE the door to each flat. Then about 3-4 years the DNO came out and replaced the main head and submains, and fitted new standard fused incomers in each flat. However at the flat in question there is nothing - just a submain cable directly in to a small termination 'head' (more like a Henley) on the meter board. The girlfriend lives next door and her's is the same (supply that is :LOL: )

Where do I go with this?
 

JohnD

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I can't quite follow this.

If you fit a 100A DP isolator, with 25mm tails connected to the Supply side, and ample length for the DNO to connect to the meter, what more do you need?

you can then fit new tails to the Load side (with the power turned off) and connect them to your old or new CU at your leisure.

I would suggest the MEM isolator and enclosure, which has a little removable cover over the Load side terminals so that you can connect to them without exposing the Supply side, which can remain sealed. However I do not think it is as strong and rigid as some more modern enclosures. It is best fitted to a strong flat surface such as a backing board, with the cables cleated to prevent any stress on the enclosure. I do not know if there is another enclosure with this feature on the market


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I can't remove the old Wylex until the supply is isolated.
Could you install the new CU, gut the old Wylex, and use its main switch as a temporary isolator to allow you to connect up the new one, finish the testing etc, so that when the DNO man comes the isolator can be installed while he is there?
 
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I can't do that because

I work for the DNO (southern electric), and we aren't allowed to connect tails from a CU to the meter/isolator on the customers side.

the DNO guy says so!


So, do I just get the DNO to de-energise, remove the old tails from the meter, connect my new ones, then get them out to re-energise? No isolators needed.

And I was hoping for a free 100A DP from the DNO! :LOL:
 

JohnD

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why can't you do what I said?

the DNO guy would just be connecting your new tails to the meter. He would not be connecting anything to the CU or the isolator on the customer's side.

The 100A DP isolator only costs a few pounds.
 
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Sorry, that reply was to JohnD, I hadn't noticed ban-all-sheds's reply! This is all getting rather complicated and confusing.

BAS, I have thought about that, but I really need the Wylex out the way so I can mount my enclosure to extend the circuits.

So, let's try and make things simple. Should I:

1) Get the DNO out to de-energise. Remove the old and connect my new tails to the meter myself. Get the DNO out to re-energise.

or

2) Get the DNO out to de-energise. Leave the old tails in the meter. Have my new tails direct from the new CU ready for the DNO guy to connect to the meter before he re-energises.

or

3) Get the DNO out to supply and fit an isolator, quickly rip the old Wylex out as soon as he pulls the main fuse, and thus be left with the load terminals on the isolator ready for me to connect my tails.

I hope it's clear what I'm trying to achieve, I don't seem to be explaining myself very well!
:LOL:
 

JohnD

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but you need be in no hurry. You can connect your CU tails to the load side of the isolator and remove the old CU at any convenient time therafter.

BTW you can ask if they will supply an isolator for you, they might. If not provide the isolator and enclosure. mounted and with the supply-side tails connected to it ready for them to connect to the meter. You are responsible for supplying new 25mm tails anyway. If it was me I would provide new 16mm G&Y and an 8-way block at the same time.
 
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JohnD-
But (s)he needs rid of the Wylex first to make space for the isolator. . .

Hibbo- is there nowhere else convenient to put an isolator? What about next to the new CU location?
 
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Hi Skenk, there's nowhere else for the isolator. There's a cupboard about 10" wide by 20" tall, with the meter at the top and the Wylex below it. I am going to mount the new CU on the adjacent wall, and all I want visible is a length of trunking between the CU and meter cupboard.

I think I'm making this more complicated - I don't NEED an isolator - if the DNO would install one for free it would have made life easier (if I could've got the Wylex out of the way in time) - but I think I'll just get it de-energised, then get them out to connect my tails (form the new CU) to the meter and re-energise.

What a palaver!
 

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