Upgrading two fuse boards to amendment 3 CU

[Diggaboy]

My first post so be gentle. And as I'm not an electrician please be patient also!

Just buying a small cottage (from son) to hopefully convert to a holiday let and obviously the fuse boards need upgrading (see pic). There are two Wylex fuse boxes (one on left supplying four storage heaters), and a Legrand CU (top left) supplying the garage via the SWA at the top of the board.



Before getting an electrician in, a couple of questions:

1. The two Wylex boxes (storage heaters and main house fuses, covers removed for clarity) will be replaced with two amendment 3 CU's. Is it better to move the Legrand CU into the garage, taking it off a spare way in a split load CU (2 RCDs) housing the main house fuses. Leaving it where it is means it will also have to be changed to Amendment 3 CU presumably, but not if it's in a non occupied garage, completely separate and some 15 metres from the house?

2. I want to get the DNO in to install 100A main isolating switch between meter and CU's but presumably with the current setup with meter and time clock, and there are three sets of tails going to the CU's, they'll need to install three isolating switches (or two if garage supply CU is removed into the garage)?

 

[Paul.M]

(admin note). Not a DIY project so left it in General section for advice.

 

[Octopus]

Best you get a local sparky to look BUT the isolation switch should really isolate ALL the fuseboards

 

[YoungScud]

While you have the DNO in, you might want to point out the poor meter wiring, for example, two tails stuffed into the load terminal of the meter. The 24 hour CU neutral is also fed straight from the cutout, when it should really be connected via the neutral block fed from the load side of the meter.

 

[Diggaboy]

While you have the DNO in, you might want to point out the poor meter wiring, for example, two tails stuffed into the load terminal of the meter. The 24 hour CU neutral is also fed straight from the cutout, when it should really be connected via the neutral block fed from the load side of the meter.

Partly why I included the pic; I did think some of the DNO wiring was a little odd, particularly the direct link from DNO fuse to the main CU.

 

[Darkwood]

Partly why I included the pic; I did think some of the DNO wiring was a little odd, particularly the direct link from DNO fuse to the main CU.

You mean the Neutral ? :juggle2:

 

[telectrix]

ifyou pops tyour location, one of us maybe close to you and give you a free quote.

 

[DPG]

You seem to know a reasonable amount of terminology which the average person wouldn't. I presume you must have an interest in the electrical side of things? Nothing intended by this, just wondering Daz

 

[Diggaboy]

You seem to know a reasonable amount of terminology which the average person wouldn't. I presume you must have an interest in the electrical side of things? Nothing intended by this, just wondering Daz

Thanks for your comments Daz, and no problem, you made a very reasonable observation. I've upgraded a few domestic boards and CU's to 17th ed., and each time had the extremely satisfying feeling of seeing the work successfully tested and approved - I bet you pros do that sort of work with your eyes closed and forgotten that feeling of pride! ;-).


I know my way around the relevant bits of 17th ed, including amendment 3, (and I'm familiar with the phrase referring to the dangers of 'a little knowledge'!) but would like to do at least some of the work, if I'm allowed to now. I guess a call to building regs and views from local sparky would answer my question, but is it acceptable to do some of the work as 'instructed person', even if it's just removing old boards, supplying the new CU's, specifying the dual load circuits, supplying appropriate RCD/RCBO's, moving garage CU, etc., but leaving the connecting, testing, issuing to a registered electrician. Once isolating switch(es) has been fitted of course!


I know it's not a good idea, even for an electrician, to just pull the DNO's twenty year old bullet, even if the load's off and wearing two pairs of marigolds and neoprene boxers! So even if all the work has to be done by an electrician, I'd prefer to see an isolating switch fitted first. It would make job timings easier and avoid waiting around time or return visits.


I've had isolating switches fitted by the DNO in my current and previous houses - took SP/Manweb twenty minutes and no charge. The DNO responsible for the cottage (isupplyenergy) have not been quite as helpful, and the call centre weren't even sure what I was talking about. If they do come out to do the job they'll charge (wouldn't tell me the charge as I'm not the owner yet), and if clutching a single 100 amp Wylex when three are needed, may just pull the cutout and come back when the job's been inspected and approved for fuse refitting....And then sparky has to come back again to test again under load.


Will try and persist with DNO and hope the supply network/meter supplier engineer is a helpful visitor (as they have been in the past), fits suitable switch isolating all three boards, and not just an expensive walk away jobsworth

 

[Diggaboy]

Thanks. Mid Wales. Dolgellau area.

(If any doubt that's a reply to telectrix! - apologies, I will get the hang of replying on the forum!)

 

[YoungScud]

I've had a chance to have a good look at the photo now, and I have one or two observations. I'm a technical trainer with the DNO you mentioned (north of the border), with metering as my specialty. I think, minimally, if you have an isolator installed, the metering guy will tidy up the substandard wiring, removing the load side phase conductor to the domestic board and placing it into the live block fed from the same meter terminal. You might also want to point out to the DNO's rep that the protection chamber at the cutout is missing from above the cablehead (this would usually be beneath the CH, but it's upside down in this case. Don't ask).

I'm not sure if you're under the impression that you need a DNO isolator for each CU. You don't. The isolator should be a 2-pole and neutral type, with one phase terminal for the 24hr board and one for the heating board (broken through the timeswitch). You would simply marshal the tails from each CU into blocks (similar to the ones already there) and take a single set of 25mm tails into the isolator terminals. If you're installing a third board, you'd need a pair of marshalling blocks for the domestic boards, giving you a single set of 25mm DI tails for connection to the isolator. The isolator, from the DNO's point of view, enables them to give you a supply without having to test your installation, as we used to many years ago.

Now, you might get lucky and get a 5 terminal meter installed, but that's a matter of luck. This would free up some much needed space on the board, but like I say, it's luck. I've done a little drawing to show roughly how the installation should look.

Edit: You've probably figured this out for yourself, but to clarify the drawing, you would only supply the marshalling blocks for your tails, not the one below the meter.

 

[Octopus]

Thanks. Mid Wales. Dolgellau area.

(If any doubt that's a reply to telectrix! - apologies, I will get the hang of replying on the forum!)

Interesting as I thought that Wales had to operate the previous version of Part P and therefore no 3rd party inspections permissible!

 

[Diggaboy]

That's really helpful YoungScud, particularly the diagram. Much appreciated. (Although it's not shown on your diagram, I assume there will be a neutral tail going from the 24hour CU into the neutral block?)

I'm expecting to move the 3rd CU into the garage (makes more sense to have it at point of use for a couple of reasons), fed via the SWA from a spare way in the 24 hour CU. If that's the case I should just need the one (Henley?) block for the neutrals from the two CU's, and single neutral tail from there into DNO isolator.

 

[Diggaboy]

Interesting as I thought that Wales had to operate the previous version of Part P and therefore no 3rd party inspections permissible!

Hi Murdoch. You're quite right and thanks for the reminder. In principle (or should that be 'in Principality'!), changes to (some aspects) of building regs since 2012 have not applied to Wales, as responsibility was then transferred to Welsh Assembly. As I understand it (and I'm getting quite giddy as I find myself well outside my sphere of expertise), third party inspection is allowable for non-notifiable work, but.....

.....just as in Englandshire, replacing a CU is also notifiable in Wales, and so I'll have to notify BC (as I've previously done, and they've always been really helpful, no matter whether it's been depth of footings, or acceptable fire alarm systems). I'm not sure what may or may not have changed in the last 3 or 4 years, so I'll have a chat with BC and a local sparky, to see what I can, or more importantly, can't do myself.

I'm fairly certain 7671, including 17th edn., and amendment 3 applies throughout UK, so I'll be looking at installing applicable CU's, fireproof cable fixings over escape routes, etc. as you all have to do over there on the wrong side of Offa's Dyke ;-)

Refurbishing a cottage for a holiday let is a classic case of needing to do everything by the book. Inspection certs will be mounted and framed in fireproof material and stored in a fireproof safe! A tourist is unlikely to spend their week drilling into a cable buried only 5 mill in the dot 'n dab, on a circuit which is the wrong side of an RCD, but the consequences of any sort of electrically caused fire in an unfamiliar house, doesn't bear thinking about.

(I've got a more than full time proper job as well so really not sure why I'm doing all of this....and a self build house extension to finish as well!).

 

[YoungScud]

That's really helpful YoungScud, particularly the diagram. Much appreciated. (Although it's not shown on your diagram, I assume there will be a neutral tail going from the 24hour CU into the neutral block?)

I'm expecting to move the 3rd CU into the garage (makes more sense to have it at point of use for a couple of reasons), fed via the SWA from a spare way in the 24 hour CU. If that's the case I should just need the one (Henley?) block for the neutrals from the two CU's, and single neutral tail from there into DNO isolator.

I believe you may actually know what you're talking about!

 

[Diggaboy]

Very good of you to say so, but I suspect I just think I know, rather than I actually do know - arguably the worst kind of diy sparky!

Just one more question (promise!) and you can go back to your day job ;-)......

..... you mentioned DNO will need to fit 2 pole isolator. Should that have read 3 pole isolator as shown in your first class diagram?The storage heater CU and 24 hour CU will obviously require separate live feeds, as you've drawn, so there'll need to be two separate lives coming in from the DNO's isolator; one going to each of my two CU's, and also a common neutral, in addition to the two live tails just mentioned?

(I suppose it's an academic question as the DNO will dictate and supply what will be fitted, but it may help if I can specify what's needed before they come out, rather than the network engineer turns up with the wrong isolator, 'should have told us mate..... see you next week, and it'll be another 50 quid!' Hopefully they'll come and look first perhaps.)

 

[YoungScud]

Very good of you to say so, but I suspect I just think I know, rather than I actually do know - arguably the worst kind of diy sparky!

Just one more question (promise!) and you can go back to your day job ;-)......

..... you mentioned DNO will need to fit 2 pole isolator. Should that have read 3 pole isolator as shown in your first class diagram?The storage heater CU and 24 hour CU will obviously require separate live feeds, as you've drawn, so there'll need to be two separate lives coming in from the DNO's isolator; one going to each of my two CU's, and also a common neutral, in addition to the two live tails just mentioned?

(I suppose it's an academic question as the DNO will dictate and supply what will be fitted, but it may help if I can specify what's needed before they come out, rather than the network engineer turns up with the wrong isolator, 'should have told us mate..... see you next week, and it'll be another 50 quid!' Hopefully they'll come and look first perhaps.)

Yes. My bad. It's a two pole and neutral. In fact, if our southern colleagues are using the same supplier as us, which they probably are, it might be a 3P &N, with one Phase terminal unused. I wouldn't envisage there would be a problem with which type they turn up with. Our guys usually carry a stock of different materials, and they will be aware of which tariff is installed at your property (they can tell meter types from the serial numbers, among other things). It is our job to know these things, so no danger of another 50 quid. Just in case anything does go wrong, it wasn't me who trained him!

 

[Diggaboy]

Yes. My bad. It's a two pole and neutral.

My apologies, 'two pole and neutral' .... that's exactly what you said in your original reply! I obviously didn't read it properly and wrongly interpreted it as just 'two pole isolator'.

.....I shall write out a hundred times, 'I must read helpful replies properly next time.....I must read helpful replies properly next time...'

 

[YoungScud]

 

[Diggaboy]

In case anyone's interested, I've just received quote (indirectly) from isupplyenergy of £68 (inc vat). Not seen details of the quote yet, but I assume that's supply and fitting of appropriate isolator (presumably by SP energy).

Slightly more than when the supplier was Npower that arranged an isolator fitting for me....well, £68 more actually as they didn't charge at all 5/6 years ago, but they may well have introduced charging since then I guess.