Kitchen Wiring

[dougie120283]

Evening all,

Before i start i don't plan to do any of the following myself and really just want to know for my own info and so i know what i ask my spark is possible (or not)

We are having our kitchen replaced over the next week. Currently the appliances dishwasher, washing machine, fridge freezer etc are all on standard sockets on the kitchen ring. The halogen hob and double oven are both connected via the same cooker control switch back to the board on a 6mm radial. The board is to 17th edition.

we are having all integrated appliances and I'd like a grid switch to provide the isolation. first question; can the grid switch be installed as part of the kitchen ring or does it need its own way on the board.

Second; our new single oven has a total connected load of 3.7 kW and the induction hob is 7kw are these OK to install on the existing single cooker circuit.

Third; we are having another combi (microwave, grill, oven) oven and is 3.1KW. Can this be installed as one of the modules on the grid switch?

Forth and final; If I buy a the correctly sized fuse modules for the grid can these all be wired adjacent to the corresponding switch in the grid and connected to the appliance via a non fused connection unit behind the appliance rather than FCU's?

Many thanks

Alex

 

[Taylortwocities]

There will obviously be some differences of approach, and i would have thought that your elecvtrician would be the b etter person to ask, rather than a DIY forum.

But anyway. My view

1. The problem with making a grid system part of a ring final is that it concentrates all of the loads at one point in the ring. The basis of a ring is that the loads are distributed around it. I would run a new 4mm radial (with 32A MCB) to feed the grid. If you must have a grid.
Remember that the cooker circuits will still remain separate.
2. The hob & oven should be OK on the existing circuit.
3. Guidance is that a fixed load of more than 2KW should not be on ring final. Your combi is even more than 13amp so really should have its own separate circuit.
4. Yes, but each appliance must be fused, somewhere.

Hope this helps.

 

[ban-all-sheds]

Your combi is even more than 13amp

No - it's about 11A.

 

[Taylortwocities]

You need new batteries in your calculator

3100/230 = 13.478

Or were you throwing in diversity? Or is your supply 280?

 

[ban-all-sheds]

Or were you throwing in diversity?

 

[ericmark]

Much depends on your electrician as to how to the letter he follows the regulations.

The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)

If he follows that to the letter then dishwasher, washing machine, tumble drier, oven, hob, and grill may all need dedicated circuits. However it would be rare to find this is the case. So ask the person doing the job no good asking on a forum.

 

[EFLImpudence]

3100/240 = 12.92A. coincidence ?

 

[JohnW2]

3100/240 = 12.92A. coincidence ?

Indeed (I presume it comes with a 13A plug). In fact (providing winston is not looking!) ...
3100 / 240 x 230 / 240 = 12.38A

As TTC is suggested, I can but presume that BAS was talking about:

{[(3100 / 230) - 10] x 0.3} + 10 = 11.04

... although maybe, as above, he should have used:

[(12.92 - 10) x 0.3] + 10 = 10.88A
or
[(12.38 - 10) x 0.3] + 10 = 10.71A

Kind Regards, John

 

[JohnW2]

1. The problem with making a grid system part of a ring final is that it concentrates all of the loads at one point in the ring. The basis of a ring is that the loads are distributed around it. I would run a new 4mm radial (with 32A MCB) to feed the grid. If you must have a grid.

As I'm sure you know, there's not really any need to have loads "distributed around" a ring final. The important point is that loads should not be concentrated near one end of the ring.

If one is talking about loads near the centre of a ring (which will probably often be the case), then even a single point load of 32A would be acceptable. Indeed, if it were right at the centre, one would have the equivalent of a 5mm² radial.

As for what 'near the centre of the ring means', if (probably unusually) the CCC of the cable were the minimum allowed (20A), then a point 32A load between about 37.5% and 62.5% of the total ring length (measured from one end) would not overload the cable. If, more commonly, the cable were 'clipped direct', the 32A load could be anywhere between about 16% and 84% of the distance from one end and still not overload the cable.

Kind Regards, John

 

[ban-all-sheds]

As TTC is suggested, I can but presume that BAS was talking about:

{[(3100 / 230) - 10] x 0.3} + 10 = 11.04

... although maybe, as above, he should have used:

[(12.92 - 10) x 0.3] + 10 = 10.88A
or
[(12.38 - 10) x 0.3] + 10 = 10.71A

I did.

it's about 11A

 

[JohnW2]

I did.

it's about 11A

Exactly my point - my (and TTC's) presumption was correct. However, as EFLI has pointed out, if (as usual) the quoted 3.1 kW relates to 240V, then one doesn't actually need diversity to get the load below 13A.

Kind Regards, John

 

[ban-all-sheds]