Different circuits in a grid switch

[AdamW]

Whats wrong with conventional methods?


David

Well, 7 FCUs would look, well, ugly.

One alternative I suppose is to run just one big ass ring or radial to power the lot on one circuit. The problem with that is, I have a Wylex with 60A main switch, so am limited to 30A MCBs. I know they do 40A but they are designed to NOT fit a 60A box... I know they fit if you modify them but I wouldn't be happy with that. A CU change is out of the question, I will only end up doing a full rewire if I fit that, as is a Henley block off to a separate CU for the kitchen (no isolator, don't fancy breaking the seal).

However I don't really feel happy with powering all the above off one 30A circuit, plus part of this exercise is to ensure the fridge is on a separate radial (never had problems with it being on the ring before, but there is always a first time). At the moment, the cooker is powered via the 30A cooker radial, fused down to 13A at an FCU. Other than that, it is all fitted to the same ring that powers every socket in the flat: again, no problems as yet but I think it could be improved.

The alternative is to run two circuits, and have two separate 4-way grids, but I would have to run the fridge off a shared ring. OK, I don't HAVE to, but I really am averse to doing all this and then having an FCU sitting there, glaring at me

I know that I would probably be OK running the cooker, dishwasher and washing machine all off a 30A radial, especially as the washing machine is hot fill. And again, that still brings in the problems of running the fridge radial through the same box.

Are you sure this isn't common? I have seen plenty of flats with a grid switch arrangement in the kitchen, seems a bit daft to go to the trouble of that, but not bother with a separate fridge radial.

 

[Damocles]

No doubt it is not common, because people only ever do things differently when they are trying to get things just the way they want them.

I think we have established that you can stuff what you like in the grid switch (assuming getting things straight inside and all the rest) and just have a label hidden behind the outer cover, but visible if you start to take it apart.

 

[plugwash]

it has been said earlier in this thread that MK supply stcikers which go on the grid with theier grids and the grid acts as a intermediate barrier (ie you can take the front plate off the grid without really exposing anything live to touching)

multiple cuircuits in a grid box is pretty common in commercial installs

 

[Lectrician]

Pubs, clubs, hotels...upto 24 switches and one circuit?? LOL

Try atleast 12 circuits, spread across phases!!!

 

[AdamW]

OK, so I think the way to do this is...

2 30A rings, one of which will power the oven, hob ignition, cooker hood and washing machine, the other which wil power everything else including sockets.

1 15A radial which will supply the fridge.

8-way grid switch, but laid out in such a way that the cables from different circuits are kept with each other rather than a spaghetti of wires making it impossible to tell. Stickers warning of multiple circuits, mounted on the front of the grid. I reckon if I can mount these over the screws/clips to remove the grid that will add visibility, as well as an extra couple for after someone has put a screwdriver through them.

Does this all sound like a reg-worthy arrangement?

 

[Damocles]

The old chestnut is the issue of whether you need to reserve one circuit exclusively for cooking, in case someone decides to go all electric. Gas is king at the moment, don't know when they reckon it will run out. Will everyone change back to coal gas or electric? If you did want to futureproof this, then I think it needs a radial rather than a ring.

Whether this is really an issue I do not know. Gas is much nicer for hob cooking.

first time I ever did that

 

[Lectrician]

We always stick in a cooker circuit regardless on new builds.

 

[Damocles]

Yep but thats because the builders want to cover every eventuality. If you do not care about the next owners then why do it?

Does anyone know how many gas hobs and how many electric are sold?

 

[pipme]

No, but I overheard this :- Three engineers were gathered together discussing the possible designers of the human body.
One said, "It was a mechanical engineer. Just look at all the joints."
Another said, "No, it was an electrical engineer. The nervous system has many thousands of electrical connections."

The last said, "Actually it was a civil engineer. Who else would run a toxic waste pipeline through a recreational area?"

Here we go Adamant :-
Normal people .... believe that if it ain't broke, don't fix it.
Engineers believe that if it ain't broke, it doesn't have enough features yet.

 

[AdamW]

Thing is, I can only find 20A-rated grid switch modules... really need 25-30A for an electric hob. So, it isn't like you would ever be able to wire a decent hob via the grid. I would rather limit the hob choice to gas for now (by using FCUs to limit the available current to electric appliances, after being switched by the grid), than to wire in a 20A switch in a way that would encourage one to use it for a 30A draw.

To look at it rationally, North Sea Gas has another 8 years of proven resources. We can import a bit more. So by the time methane has become really expensive, this kitchen will be old-fashioned and dated. If they decide to go to an electric hob, they will be due for a rewire by then anyway (25 year installation life).

So by NOT installing a dedicated hob circuit, I would in fact be IMPROVING safety by FORCING a rewire at an installation age of 25 years, when the gas runs out... Am I a considerate bloke or what?

 

[securespark]

But not in grid switches, where you often find two or three different circuits present, especially in a com environment, but more so in dom now as well.

My concern would be how to loop the 6mm2 (?) live and neutral feeds from one module to the next.

 

[AdamW]

My concern would be how to loop the 6mm2 (?) live and neutral feeds from one module to the next.

Hence why I have given up on the 30A radial idea and will install 30A rings instead! 2.5mm cable, much nicer to work with. 4mm radial to fridge should be no hassle.

I have the feeling that I am vastly overengineering this. When wiring a kitchen they put a separate ring in, but does this power everything, appliances AND sockets? With my current plan I will have 75A worth of circuits supplying the (rather small) kitchen. Diversity and all that, but my main fuse is only 60A!

Am I approaching this the right way?

15A radial for fridge/freezer: sensible precaution I think
30A ring for oven, washing machine and dishwasher, + hob ignition and cooker hood (the last two being occasional/low drain)
30A ring for the sockets + microwave.

I reckon this is correct as I want to have the option to cook whilst washing clothes and dishes, and even if I didn't want to someone in future probably would. And whilst I would never use 30A off the sockets (5A for a microwave, 10A for a fast-boil kettle, 5A for a toaster) I can't see any point in wiring a ring with a lower capacity.

 

[ban-all-sheds]

15A radial for fridge/freezer: sensible precaution I think

Indeed, but 4mm² cable for it??

 

[AdamW]

I was making an assumption because the immersion radial which follows the same run) is also in 4mm. But on reflection that is vastly overkill for a fridge. The run is about 4m vertically upwards in a solid wall (I am hoping in conduit, but can't get to it to check without a lot of upheaval) then 8m clipped direct to loft joists. Finally, 3m down in a solid wall (will be in conduit).

Perhaps 2.5mm will be more appropriate! I can't imagine anyone installing a commercial fridge in there that needs 30A or so.

Sometimes things seem so obvious until you actually talk it over, then someone points out areas where you are making more work for yourself.

 

[Damocles]

Do it the way you want it. Assuming the oven, washing machine and dish washer will all fit on one 32A circuit, then on balanceI like it. my first reaction was that you were loading all the heavy items on one circuit and none on the other. But if they do all fit, then maybe leaving all the spare on the sockets makes good sense.