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Replacing a consumer unit

Does what it says on the tin
DrFfybes
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Replacing a consumer unit

#509932

Postby DrFfybes » June 27th, 2022, 9:09 am

I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.

We both decided the consumer unit (dated 1984) is still OK, however we want to extend, fit solar panels, and probably a car charger, and there are no spare ways on the old plastic box, so he has agreed to replace it.

However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.

Anyone else come across this?

Paul

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Re: Replacing a consumer unit

#509939

Postby Mike4 » June 27th, 2022, 9:36 am

DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.

We both decided the consumer unit (dated 1984) is still OK, however we want to extend, fit solar panels, and probably a car charger, and there are no spare ways on the old plastic box, so he has agreed to replace it.

However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.

Anyone else come across this?

Paul



Curious. I had new consumer units fitted in all of my BTLs a while back, and this issue did not arise.

AsleepInYorkshire
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Re: Replacing a consumer unit

#509941

Postby AsleepInYorkshire » June 27th, 2022, 9:44 am

DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.

We both decided the consumer unit (dated 1984) is still OK, however we want to extend, fit solar panels, and probably a car charger, and there are no spare ways on the old plastic box, so he has agreed to replace it.

However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.

Anyone else come across this?

Paul

Is he NICEIC qualified?

AiY(D)

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Re: Replacing a consumer unit

#509943

Postby 88V8 » June 27th, 2022, 9:46 am

DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.....the old plastic box....
However, he says that he is no longer allowed to pull the main fuse....

I don't know if all CUs are now in a metal box with a fall-shut lid, but if not that's what I would recommend as they will contain any fire arising in the CU.

I also recommend you fit an RCBO on every circuit, rather than an RCD.

When our CU was replaced three years ago the main fuse was not touched, the electrician just pulled out the (live) tails and popped a rubber glove over them. Before reconnecting he ensured all load was off so there was no spark.

V8

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Re: Replacing a consumer unit

#509944

Postby staffordian » June 27th, 2022, 9:55 am

88V8 wrote:
DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.....the old plastic box....
However, he says that he is no longer allowed to pull the main fuse....

I don't know if all CUs are now in a metal box with a fall-shut lid, but if not that's what I would recommend as they will contain any fire arising in the CU.



V8

I think I read recently that any new unit has to be metal; not sure about top hinged, but that makes sense.

Must be quite a new update as we had a new one about six or seven years ago which is plastic.

DrFfybes
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Re: Replacing a consumer unit

#509955

Postby DrFfybes » June 27th, 2022, 10:17 am

88V8 wrote:
DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.....the old plastic box....
However, he says that he is no longer allowed to pull the main fuse....

I don't know if all CUs are now in a metal box with a fall-shut lid, but if not that's what I would recommend as they will contain any fire arising in the CU.

I also recommend you fit an RCBO on every circuit, rather than an RCD.

When our CU was replaced three years ago the main fuse was not touched, the electrician just pulled out the (live) tails and popped a rubber glove over them. Before reconnecting he ensured all load was off so there was no spark.

V8


Metal boxes are now a requirement.

Individual RCDs on each circuit and standard 'Fuses' for the main incoming, and for the 6mm feeding the garage box. It is always the RCD nearest the supply that trips anyway (ie the one on the whole board if fitted) so subsiduary ones very rarely did anything.

He can't remove the tails from the fuse box end as subsent work has built around the unit so there is no access to where the supply comes in without channelling out a stud wall and risking damaging the tails (which are trapped and might need replacing anyway - maybe this should add to the 'bodgetastic' thread). Once it is isolated then the unit will need to be moved a few inches and all the circuits extended.

AsleepInYorkshire wrote:Is he NICEIC qualified?

NAPIT, with 18th Ed cert. Mainly he does testing, and he is rather geeky. I redid the shed first fit under his guidance, metal clad (MK) boxes (which aren't cheap but I am clumsy), routing visible but protected, bottom entry to all boxes and fittings in case of leaks. He also suggested a firebreak between each socket/switch and the shed, and suggested glands on each entry point to trap fire, though on a shed 30 feet from the main house it isn't a necessity.

Mike4 wrote:Curious. I had new consumer units fitted in all of my BTLs a while back, and this issue did not arise.


He said it was because when they fitted the smart meters they crimped and sealed the incoming fuse, otherwise he would have pulled that.

Paul

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Re: Replacing a consumer unit

#509957

Postby Itsallaguess » June 27th, 2022, 10:23 am

DrFfybes wrote:
He said it was because when they fitted the smart meters they crimped and sealed the incoming fuse, otherwise he would have pulled that.


It's very surprising how feeble those crimped seals can be on incoming fuses.

They fall off and disappear all the time in my experience, with no subsequent issues so far...

It might have been a knock with a hoover being put away. It might have been those darned mice again...

It really is quite spooky...

Cheers,

Itsallaguess

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Re: Replacing a consumer unit

#509966

Postby 88V8 » June 27th, 2022, 10:38 am

Itsallaguess wrote:
DrFfybes wrote:He said it was because when they fitted the smart meters they crimped and sealed the incoming fuse, otherwise he would have pulled that.

It's very surprising how feeble those crimped seals can be on incoming fuses.
They fall off and disappear all the time in my experience, with no subsequent issues so far...
It really is quite spooky...

Yes, it seems to be a common problem, given the number of sellers on eBay offering seals and crimp tools.

DrFfybes wrote:
88V8 wrote:I also recommend you fit an RCBO on every circuit, rather than an RCD.

Individual RCDs on each circuit and standard 'Fuses' for the main incoming, and for the 6mm feeding the garage box. It is always the RCD nearest the supply that trips anyway (ie the one on the whole board if fitted) so subsidiary ones very rarely did anything.

My point, which I think more learned members have previously enlarged upon, is that RCBOs, as distinct from RCDs, do not cause the nuisance tripping of the whole house that you have experienced. Only the offending circuit trips.

DrFfybes wrote:He can't remove the tails from the fuse box end as subsent work has built around the unit so there is no access to where the supply comes in without channelling out a stud wall and risking damaging the tails (which are trapped and might need replacing anyway - maybe this should add to the 'bodgetastic' thread). Once it is isolated then the unit will need to be moved a few inches and all the circuits extended.


Ahh, so the existing tails are in effect to be abandoned. That's a pain. When our CU was moved & renewed, the tails were long enough.

Well, I think IAAG has solved that one for you.....

V8

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Re: Replacing a consumer unit

#509968

Postby AsleepInYorkshire » June 27th, 2022, 10:48 am

Id suggest you contact your DNO (District Network Operator). Different companies have different solutions for this situation. You'll need to discuss it with them.

https://selectra.co.uk/energy/guides/di ... -my-dno-uk

AiY(D)

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Re: Replacing a consumer unit

#510045

Postby quelquod » June 27th, 2022, 4:45 pm

DrFfybes wrote:However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment.

Did he mention how the supplier can tell the difference remotely between the main fuse being pulled and the main switch being opened or a whole house RCD tripping? Just throw the seal away and tell him you’ll yank the fuse yourself - no one will care.

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Re: Replacing a consumer unit

#510099

Postby modellingman » June 27th, 2022, 8:38 pm

DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.

We both decided the consumer unit (dated 1984) is still OK, however we want to extend, fit solar panels, and probably a car charger, and there are no spare ways on the old plastic box, so he has agreed to replace it.

However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.

Anyone else come across this?

Paul


Not come across that but a few things that he will likely focus on, particularly if your consumer unit is that old - mine was fitted in 1996 and was described as an "antique" by my electrician when he certified the installation in preparation for an upcoming sale of the house. These are
  • Cross section of meter tails - I think mine were 16 mm2 whereas 25mm2 seems to be the current minimum requirement
  • Cross section of earth straps onto incoming water and gas services - the requirements have been upped, apparently from 16th edition which applied when my house was rewired in 1996 and the current 18th edition
  • Multiple RCDs rather than just one so not all power is lost from a nuisance trip - think that came in with the 17th Edition (as another poster has mentioned RCBOs are an alternative
  • Effectiveness of earthing arrangements - my installation has a meter long earth rod which required removal and cleaning to get the resistance down below the required threshold

I was also surprised when my electrician mentioned that the "curve" on my equipment (MCB's, I think) was now obsolete. Greater reliance on wind generation causes, apparently, problems with transient currents on the grid, meaning different "curves" are now fitted in new installations. Who knew? He did manage to replace one of my broken "antique" MCBs using a source on eBay, but that shouldn't be a problem for you as you are having the whole CU replaced. Hope you have a lengthy and substantial piece of wall to mount it on, you will probably need it! And it will be metal.

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Re: Replacing a consumer unit

#510120

Postby SteelCamel » June 27th, 2022, 10:47 pm

DrFfybes wrote:However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.


Technically it's always been illegal to pull the main fuse. But the electricity companies generally turn a blind eye to it, as it's far safer than working live.
I don't see that the smart meter makes much difference - it belongs to the supplier, not the distributor. And pulling the main fuse is indistinguishable from a power cut. If the supplier really wanted, they could see that the smart meter lost power and confirm with the distributor that there wasn't a power cut at that time, but it would be a lot of work and wouldn't really gain them anything.
But yes, the best solution is to fit an isolator - between the meter and the CU, not between the fuse and the meter. The supplier may install one if you ask, or you can get your own installed - which of course requires pulling the main fuse in order to install...

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Re: Replacing a consumer unit

#510170

Postby raybarrow » June 28th, 2022, 9:49 am

Hi Folks,
It's very surprising how feeble those crimped seals can be on incoming fuses.

They fall off and disappear all the time in my experience, with no subsequent issues so far...

It might have been a knock with a hoover being put away. It might have been those darned mice again...

It really is quite spooky...


That takes me back. I used to work for NORWEB, MEB, nPower and those seals are so easily broken. Like the coin boxes on prepayment meters, when they collected real money. Amazing how strong, little babies and pets were in those days.

Ray.

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Re: Replacing a consumer unit

#510190

Postby Mike4 » June 28th, 2022, 10:43 am

raybarrow wrote:Hi Folks,
It's very surprising how feeble those crimped seals can be on incoming fuses.

They fall off and disappear all the time in my experience, with no subsequent issues so far...

It might have been a knock with a hoover being put away. It might have been those darned mice again...

It really is quite spooky...


That takes me back. I used to work for NORWEB, MEB, nPower and those seals are so easily broken. Like the coin boxes on prepayment meters, when they collected real money. Amazing how strong, little babies and pets were in those days.

Ray.


And reputedly back in the day, gas meter fitters would occasionally and accidentally fit them with the display against the wall. This is most unfortunate as you can imagine, as it makes the meter run backwards and incorrectly record the amount of gas used. A bit of a nuisance for everyone concerned...

I doubt that works with modern meters.

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Re: Replacing a consumer unit

#510209

Postby quelquod » June 28th, 2022, 11:50 am

I’m told that student flats back in the day often had failed meter seals and mysterious scratches on the screws to the voltage coil. Probably apocryphal.

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Re: Replacing a consumer unit

#510766

Postby csearle » June 29th, 2022, 8:40 pm

DrFfybes wrote:I have finally found a reasonable, communicative, and most importantly available electrician to sort out the rambling hotchpotch that is in our ageing house.

We both decided the consumer unit (dated 1984) is still OK, however we want to extend, fit solar panels, and probably a car charger, and there are no spare ways on the old plastic box, so he has agreed to replace it.

However, he says that he is no longer allowed to pull the main fuse, as now we have smart meters the suppliers know someone is in their equipment. I know our smart meter is old style from a different supplier, and i submit readings each month, so it is unlikely to alert him, but he sa#ys I need to get the supplier to fit an isolator between the fuse and the meter.

Anyone else come across this?
Not come across any specific requirements for "smart" meters but generally there is a conflict for electricians when it comes to service heads. The Health and Safety Executive would have issue with us operating on a live circuit when it could be dead (by pulling the service fuse). On the other hand we are not allowed by the DNOs to touch service fuses (I've heard that you are supposed to wear a mask as you replace the fuse-carrier in case it blows as you do it! I have no evidence to back up this assertion).

In practice inserting live tails into a metal board is impractical. The plastic boards were another matter. An isolator between the meter and the consumer unit is a splendid idea. I'd go for it if you can.

I cannot really see - as has pretty much been said - how a smart meter could distinguish between a power cut and the service head fuse being pulled. (Don't tell anyone but if necessary I work on dead circuits by pulling the fuse and requesting the client contact the DNO afterwards to have a seal put back on it.)

Chris

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Re: Replacing a consumer unit

#510767

Postby csearle » June 29th, 2022, 8:47 pm

AsleepInYorkshire wrote:Is he NICEIC qualified?
NICEIC is just one organisation. There are others (with more onerous prerequisites for membership) for example NAPIT. C.

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Re: Replacing a consumer unit

#510769

Postby csearle » June 29th, 2022, 8:55 pm

88V8 wrote:I don't know if all CUs are now in a metal box with a fall-shut lid, but if not that's what I would recommend as they will contain any fire arising in the CU.

I also recommend you fit an RCBO on every circuit, rather than an RCD.

When our CU was replaced three years ago the main fuse was not touched, the electrician just pulled out the (live) tails and popped a rubber glove over them. Before reconnecting he ensured all load was off so there was no spark.
Yes all new CUs must be (ferrous) metal boxes. With this they are curing the symptom (fire) rather than the problem (shoddy single-screw terminals).

An RCBO is an RCD. (An RCD is am umbrella term for any device with residual-current protection) like an RCBO or an RCCB.

The only way an electrician would connect a metal consumer unit without pulling the service fuse would be if there was an isolator, a meter with an isolator, or by inserting a "Henley block" (basically a junction box) between the meter and the metal consumer unit.

Anything else would be unacceptably risky I feel because, whatever handwear he/she was wearing, accidentally dabbing a live tail on a metal box as it was introduced would make the whole box live. This is a circumstance that would be avoided by anyone concerned with safety.

C.

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Re: Replacing a consumer unit

#510771

Postby csearle » June 29th, 2022, 9:01 pm

DrFfybes wrote:It is always the RCD nearest the supply that trips anyway (ie the one on the whole board if fitted) so subsiduary ones very rarely did anything.
My observations have not been so clear cut. I do an awful lot of testing and often come up against RCD "selectivity" issues (as it is now called - used to be called discrimination). I have found it to be fairly random which RCD trips. Usually it is the same one, upstream or downstream, but often it can be different RCDs whilst repeating the same test (the test being a 30mA test-leak to Earth and a 150mA leak to earth [first on the positive half-cycle then on the negative one]). C.

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Re: Replacing a consumer unit

#510772

Postby csearle » June 29th, 2022, 9:20 pm

modellingman wrote:Cross section of meter tails - I think mine were 16 mm2 whereas 25mm2 seems to be the current minimum requirement
Basically 25sqmm for a 100A main fuse; 16sqmm for a 60A main fuse.

modellingman wrote:Cross section of earth straps onto incoming water and gas services - the requirements have been upped, apparently from 16th edition which applied when my house was rewired in 1996 and the current 18th edition
Main protective bonding has to be upgraded to 10sqmm. Used to be 6sqmm a long time ago.

modellingman wrote:Multiple RCDs rather than just one so not all power is lost from a nuisance trip - think that came in with the 17th Edition (as another poster has mentioned RCBOs are an alternative
At some stage a requirement was introduced stipulating that a safety device should not effect more than one circuit. This was stipulated ages ago then universally ignored by the industry, which continued churning out "split-load" boards, which to my mind never fulfilled this requirement. Even now such CUs can be bought, and many are installed. They are all rubbish (because they fail to meet this requirement) and I personally never, never install them. I go for individual RCBOs on each circuit.

modellingman wrote:Effectiveness of earthing arrangements - my installation has a meter long earth rod which required removal and cleaning to get the resistance down below the required threshold
Incredible. IIRC 200ohms is the threshold. Usually, even on the driest of days, you can better this. Cheaper solution is to pour a bucket of water over the earth stake and measure again! So long at there is some kind of RCD protection then it is of almost no consequence.

modellingman wrote:I was also surprised when my electrician mentioned that the "curve" on my equipment (MCB's, I think) was now obsolete.
The curves of an MCB/RCBO apply to the current/time curves of their operation (BS60898, BS61009-1). They are all depicted in the wiring regs. (BS7671). They have not changed in the last 30 years (to my knowledge). What has changed recently is the tolerance of RCDs to pulsating DC as opposed to AC, made more important with the proliferation of LED lighting.

Chris


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