UK Grid / Minigrid wiring to an unswitched socket for kitchen appliances.

[daavvee]

Okay, so, I’m currently working towards becoming an electrician and was after some guidance for a job that I’m working on.

The property (a small flat) has a few circuits on RCBOs.
1 Ring (kitchen)
1 Radial Sockets
1 Internal Lighting
1 External Lighting

The owner occupier is replacing their kitchen and is wanting grid switches as a means to isolate their appliances:

Fridge freezer
Igniter on gas hob
2kW oven
Washing machine

I’m looking at Click Minigrid.

There doesn’t seem to be any clear guidance on the grid switches be that from the manufacturer or otherwise.

The grid switches are 13A double pole. Now some say they need their own fuse, other say they don’t if the device they’re coming trolling has its own fuse such as a that found in a plug top, others say it needs to be a radial, other say it can be done off a ring.

I’m figuratively pulling my hair out.

So, for my question...

Can these grid switches be used on a ring main without the need for a fuse on the grid plate, if so, can someone show me and/or explain how they would be wired?

I’m thinking it would be:

Incoming supply to the grid switch (from ring main) feeds an unswitched socket from the ‘outgoing’ load on the grid switch. The fuse would be in the plug top on the appliance.

To continue the ring, this is looped in and out at the grid switches.

See Image (forgive the artwork)
edit here’s a link to the grid switches - https://www.electricalcounter.co.uk...P+Switch+Module,+'WASHING+MACHINE'/2454004957

 

[littlespark]

I would be careful with that amount of load running through one area of the ring. Grids are notorious for tight cables, give yourself a deeper backbox if you can.

Your drawing is wrong, as it’s not a ring.

I would put the oven on its own radial, but mounted in the same grid, the ring looped through the other 3 switches.

Think of it as spurs coming from the ring from different positions, you don’t need to fuse down at each switch.

 

[telectrix]

separate circuit to the grid switches, either a ring in 2.5mmor a radial in 4mm. (either way on a 32A MCB/RCBO). switches should be 20A D/P.

 

[daavvee]

I would be careful with that amount of load running through one area of the ring. Grids are notorious for tight cables, give yourself a deeper backbox if you can.

Your drawing is wrong, as it’s not a ring.

I would put the oven on its own radial, but mounted in the same grid, the ring looped through the other 3 switches.

Think of it as spurs coming from the ring from different positions, you don’t need to fuse down at each switch.

Thanks.

I realised after I posted, I’d not drawn the outgoing leg of the ring.

 

[daavvee]

I would be careful with that amount of load running through one area of the ring. Grids are notorious for tight cables, give yourself a deeper backbox if you can.

Your drawing is wrong, as it’s not a ring.

I would put the oven on its own radial, but mounted in the same grid, the ring looped through the other 3 switches.

Think of it as spurs coming from the ring from different positions, you don’t need to fuse down at each switch.

Thanks for the insight RE the back box and for the tip on the oven.

Am I correct in that I'd wire up everything as per my (new) picture for implementing the grid switches into a ring with incoming and outgoing legs looping between the supply side of the switches?

Where you say that the oven should ideally be run off its own radial. I'm guessing I'd run it through the 'oven' switch on the grid as I would with any ordinary cooker switch? As it's only 2kW, could this not be run off a 20A RCBO with 2.5mm T&E?

I'd be grateful for any insight.

I've added two images that I've drawn this morning, if someone could clarify if this is the correct way to wire the switches as a ring (looping in and out of the switches and treating the loads as spurs) and the second image which omits the oven from the ring and has this as its own radial.

Thanks so much in advance.

 

[westward10]

I see you are a trainee so is this a private job or something you are undertaking for your employer.

 

[daavvee]

I see you are a trainee so is this a private job or something you are undertaking for your employer.

This is a private job that is then going to be tested and signed off. Any reason?

 

[daavvee]

separate circuit to the grid switches, either a ring in 2.5mmor a radial in 4mm. (either way on a 32A MCB/RCBO). switches should be 20A D/P.

Thanks.

Any reason I’d need 20A rather than 13A when the load on each is less than 13A?

am I correct in saying you would leave kitchen sockets on their own ring and have the grid switches on a new ring circuit?

 

[littlespark]

Thanks.

Any reason I’d need 20A rather than 13A when the load on each is less than 13A?

am I correct in saying you would leave kitchen sockets on their own ring and have the grid switches on a new ring circuit?

Because dp switches come rated at 20A....

The grid can be part of the same ring as the kitchen, but be aware of high power items that could overload the circuit if all on at the same time.

The oven is the highest draw that I can see. Put it on its own radial.

 

[brianmoooore]

Any 'fixed' appliance 2kW or over (in this example, the oven), should have its own dedicated supply from the CU.
Igniter and fridge/freezer are trivial loads, and wash/mac. is a high, but very intermittent load, so these three could come off of the existing RFC. They will need fusing downstream from the switches.

 

[pc1966]

In most cases the grid switches will be feeding an unswitched 13A socket, or maybe a FCU, so you have your <= 13A fuse there.

But definitely a deep back-box!

 

[Lister1987]

This is a private job that is then going to be tested and signed off. Any reason?

Nothing personal on you @daavvee , just due diligence, and probably a polite advert (to follow) to join our trainees section in a slightly 'less hostile' area of the forum.

The difference between how public doing thier own electrics and trainees doing electrics is the whole 'a little knowledge can be dangerous' thing, the trainee section allows the seeking of advice and better steering towards an outcome, with a bit of creative feedback in the process, plus there are others in your position too ?

 

[richy3333]

Hostile, this forum, never ???

 

[loz2754]

Because dp switches come rated at 20A....

Indeed. However, the data sheet for Click Mini Grid Double Pole single module switches says they are 13 amp (resistive) ,10AX.
This is not something I've come across before.
Could be confusing for the less experienced.
I would be inclined to (not install appliances on a grid system, just my personal preference) install a proper grid switch system with the DP switches rated at 20 amps.

 

[pc1966]

Some grid switches are intended for lighting and 10A or so rated, others are 20A, typically the DP switches, so you do need to check the spec carefully!