Considering CU update

[dormermike]

Has he ever heard of a 'cooker'? An oven and hob in one and what the label on the circuit breaker states.


Well, the ratings will be quoted at 240V, at 230V the Wattage will be less - but that doesn't make much difference.
As I have shown you, the design current of the circuit is 22A.
I don't blame you for being wary but the system has been in use for decades - and works.


35 is more than 22 so fine.


You could get a new - or probably better would be an older - electrician.

10mm² is used for the supply cable to many premises to supply everything; cooker, heating, shower, everything; as they (and you might) only have a 60A main fuse.
I wonder how that works.

Thank you again. Honestly yes I think getting another electrician in is probably the best approach. Considering not one of the ones I had in already even thought to pop off the cover of the oven isolator to see what the existing supply cable is.

Thanks again, have a good evening.

 

[flameport]

Electrician saying diversity for an oven and hob on same circuit is hard to justify, as they're frequently operated together. Also that "12000 / 230v gives approx 52.2 amps,

Above images from the current version of the On Site Guide, which your electrician surely must have a copy of.
It's also in the previous editions.

The concept of diversity for cooking appliances first appeared in the Wiring Regulations 90 years ago in 1934, so there is absolutely no excuse for any electrician alive today to be unaware of it.

I'm going to have to get a new 6mm or even 10mm circuit put in

No.

 

[blup]

Only thing I'm not entirely sure about is he is saying for downlights it's ok to run the cables under the joist, i.e. not through the joist. Not sure I'm happy about that... Any thoughts ?

Its possible to fish through a 1mm cable between the gaps in lath and plaster ceilings. Otherwise take up floorboards in room above. You can save time and money by removing tne floor coverings.

 

[Murdochcat]

Its possible to fish through a 1mm cable between the gaps in lath and plaster ceilings. Otherwise take up floorboards in room above. You can save time and money by removing tne floor coverings.

Or, if your home has floors made out of large sheets of wood, do it from below and get the ceiling skimmed.

Don't like the bodge of cutting slots in the ceiling and avoiding the joists

 

[dormermike]

Or, if your home has floors made out of large sheets of wood, do it from below and get the ceiling skimmed.

Don't like the bodge of cutting slots in the ceiling and avoiding the joists

Yep, that's what i'm leaning toward. I don't want the joists touched, and the upstairs is half eaves and half bedroom, boarded with 18mm chipboard (yuck!) so i'm thinking we overboard the ceiling and skim it. Have had a plasterer in and its not that expensive in the scheme of things.

 

[JohnW2]

Hi again. Electrician saying diversity for an oven and hob on same circuit is hard to justify, as they're frequently operated together.

As has been said, it appears that you probably need to find an electrician who knows what he is doing and talking about. If items, or parts of items, were not "frequently operated together", there would be no need for the concept of diversity.

The point that your current electrician doesn't seem to understand is that, although the oven and hob will be "frequently operated together", all parts (heating elements, hot plates etc.) of both would never be drawing current simultaneously for appreciable periods of time, since they are all thermostatically controlled.

Also that "12000 / 230v gives approx 52.2 amps, therefore 6mm cable not suitable under any installation method, as max current is 47A, ...

See above.

... even before derating to 35A for being in a wall/conduit and not clipped".

Again, he doesn';t seem to understand. The curerent rating of a cable "in a wall" is the same as if it is 'clipped' to the surface of the wall. (the rating does decrease if 'in conduit').

AS they're the one signing off I think I'm going to have to get a new 6mm or even 10mm circuit put in "10mm flat cable max current for ref method c is 64 amps, and for ref method 102 is 47 amps".

Again, it would seem that you probably need a competent electrician.

 

[blup]

Yep, that's what i'm leaning toward. I don't want the joists touched, and the upstairs is half eaves and half bedroom, boarded with 18mm chipboard (yuck!) so i'm thinking we overboard the ceiling and skim it. Have had a plasterer in and its not that expensive in the scheme of things.

How do you avoid the joists with 12 downlights, the cable's got to go through the joists at least twice if the lights are spread evenly round the room.

 

[dormermike]

How do you avoid the joists with 12 downlights, the cable's got to go through the joists at least twice if the lights are spread evenly round the room.

The room is 4.5m wide, and half of it is boarded out eaves/attic and the other half is a bedroom. I'm hoping we can cut holes via the boarding in the eaves and thread it through. Use more cable, but cables cheap.

 

[dormermike]

As has been said, it appears that you probably need to find an electrician who knows what he is doing and talking about. If items, or parts of items, were not "frequently operated together", there would be no need for the concept of diversity.

The point that your current electrician doesn't seem to understand is that, although the oven and hob will be "frequently operated together", all parts (heating elements, hot plates etc.) of both would never be drawing current simultaneously for appreciable periods of time, since they are all thermostatically controlled.

See above.

Again, he doesn';t seem to understand. The curerent rating of a cable "in a wall" is the same as if it is 'clipped' to the surface of the wall. (the rating does decrease if 'in conduit').


Again, it would seem that you probably need a competent electrician.

Thank you John

Struggling to find a new electrician but looking. According to one of the ones I've had in, the 6mm cable must be protected with a 32amp rcbo, hence needing two circuits. I feel like I've tried to do the right thing by getting sparks in but frankly it's been a bit of a waste of time. Frustrating.

Ps the cable is in wall but that may be in conduit, not possible to say yet.

 

[JohnW2]

Thank you John Struggling to find a new electrician but looking.

Judging by what you go on to say, I think you probably should keep trying.

I feel like I've tried to do the right thing by getting sparks in but frankly it's been a bit of a waste of time. Frustrating.

You have my sympathy. I imagine that most electricians are reasonably competent, but it seems as if you have been unlucky.

Kind Regards, John

 

[EFLImpudence]

Struggling to find a new electrician but looking. According to one of the ones I've had in, the 6mm cable must be protected with a 32amp rcbo, hence needing two circuits. I feel like I've tried to do the right thing by getting sparks in but frankly it's been a bit of a waste of time.

You have my sympathy.

What about ringing NICEIC and asking them if they have any real electricians who know what they are doing?

 

[Murdochcat]

You have my sympathy.

What about ringing NICEIC and asking them if they have any real electricians who know what they are doing?

They only know ones who pay up each year

Ask friends and neighbours locally is my advice

 

[JohnW2]

They only know ones who pay up each year

Indeed.

Ask friends and neighbours locally is my advice

That's what we all usually say, since it's about the best we have to suggest. However, whilst friends and neighbours can comment on such issues as tidiness, punctuality, politeness/pleasantness etc., very few of them are able to make a judgement of an electrician's knowledge or skills, nor even if they are 'safe' to be let lose on an electrical installation!

 

[EFLImpudence]

I meant ring NICEIC to be mischievous and make a point.

 

[dormermike]

Well I thought I'd update this thread

Due to time constraints I ended up going with one of the guys who had quoted. He said initially he would make it work with a new 2.5mm cable from the CU. I said it you're going to run a new cable rather than off the ring, you may as well run 4mm given the cost difference in the cable. If you may recall this was because he wouldnt run the ovens and hob off the already installed 6mm cable. Anyway, long story already long and not getting any shorter the cable that ended up getting installed wasn't 2.5mm it wasn't 4mm, but an additional 6mm. Confused look on my part prompted the response "well, considering the price difference from 4mm to 6mm we thought we may as well put 6 in". Got to lol, nowt else we can do. So now I've 12mm total CSA of cables supplying the kitchen cooking appliances. Diversity? Ohms law? Environment? Naww, just belt and braces rather than really understanding