Grid Switches radial wiring acceptable or not?

[Scotsman2k6]

Hello Electrical world.

Looking for thoughts and opinions. Currently planning out my kitchen re-wire for new kitchen.

I was originally planning on having my washing machine 9.1A, tumble dryer 6.5A, dish washer 8.5A on there own radial circuit. Total current 24.1A, protected by a 25A circuit breaker, on a radial circuit. Then i thought about having them all controlled by grid switches.

This is the part i require feedback.

For wiring them up, is it perfectly acceptable to have them wired up as a radial through the grid switches protected by a 25A breaker. I am aware that the grid switches are only rated at 20A. Which is why i'm wondering if i would be better to split them onto two circuits and i could also fit my cooker hood into a grid switch that would be fused.

Although ive seen videos on youtube of a 4mm cable being split over two grid switches and on the supply side having 2.5mm cable, is this acceptable?

 

[littlespark]

24A on a 2.5mm cable is pushing its current capacity which can be a lot lower depending on its installation method. (Through insulation for example)

A separate 16A, 2.5mm radial circuit for the washing machine and dishwasher… as both are over 2kW (or very near it)
Another radial for dryer and hood.

The 20A rating of the switch is only for the individual load connected to each switch. Your maximum is 9.1 so that’s ok.


Grid switches can get tight to work on. Give yourself a 47mm back box for a little extra room.

4mm in a gridswitch would be very hard to work on… trying to get 2 into a terminal.

 

[pc1966]

If you want a single radial circuit in 4mm then you might be better to have some 5-way Wagos in the grid box for 3 * 2.5mm out to each switch.

2.5mm for the appliances is OK as they should have 13A fuses anyway so you can't overload the cable, and 25A the RCBO (or MCB+RCD) gives adequate fault protection prior to the socket outlet.

 

[Scotsman2k6]

24A on a 2.5mm cable is pushing its current capacity which can be a lot lower depending on its installation method. (Through insulation for example)

A separate 16A, 2.5mm radial circuit for the washing machine and dishwasher… as both are over 2kW (or very near it)
Another radial for dryer and hood.

The 20A rating of the switch is only for the individual load connected to each switch. Your maximum is 9.1 so that’s ok.


Grid switches can get tight to work on. Give yourself a 47mm back box for a little extra room.

4mm in a gridswitch would be very hard to work on… trying to get 2 into a terminal.

Thanks for sharing your knowledge mate. If i were to have multiple circuits inside the grid switch station, is this acceptable, i would think so as its an isolation point but just curious.

 

[pc1966]

Having multiple circuits in the grid switch should be fine, but I personally would label it inside to that effect. just in case some DIY person in the future fails to realise it.

In the UK with our 13A sockets (or FCU) we have the luxury of allowing any reasonable size current limit to that point as the fuse takes over when it comes to the appliance protection. That is why we can have 32A ring finals or radials, where as EU is limited to what is safe for the appliance flex, etc.

So in places like France they would insist on 3 * 16A radials for this, and there is a logic to it, but it means more RCBOs (they also have much larger CUs and, more importantly, regulations on the space around them!)

You could do the same, but on the assumption they are DP switches you don't need to as if one is faulty (even N-E fault tripping RCD side) you can easily find out with the use of the switches. So you can put in 25A or 32A.

Now if you want to avoid buying both 4mm and 2.5mm (which you might have) you could put in 2*2.5mm to the grid switch and treats it like a ring. Simply paralleling them to some 5-way Wagos (then 3 *2.5mm out) is also an option and perfectly good, but if you want to terminate on just the grid switch terminals doing that means 2 wires at each switch.

 

[littlespark]

This back box is getting deeper and deeper....

 

[pc1966]

This back box is getting deeper and deeper....

They are never deep enough!

 

[Scotsman2k6]

I think 4mm radial inside a back box is do able. I watched a video of someone fitting one in a 35mm the other day

 

[pc1966]

Look for the deepest back box you can fit in.

A few places sell T&E in short-ish lengths, some by the metre, so you can get what you need without masses of cable left over.

 

[davidsparky]

I often fit grid switches on site supplied via a ring final with loads to various appliances- cooker hood, washing machine , dishwasher, fridge freezer.
2x 2.5mm for ring and 4x2.5mm to each appliance in a 35mm back box no problem.

 

[pc1966]

...35mm back box no problem.

I guess that is the minimum. mostly I have used metal box grid switches and they are tight.

 

[davidsparky]

I guess that is the minimum. mostly I have used metal box grid switches and they are tight.

Yes definitely always use a 35mm deep box as a minimum but 47mm definitely makes life easier as can be a bit of faff in 35mm but not an issue if cut to length and dressed neatly

 

[freddo]

They are never deep enough!

Flat plate grid dimmers spring to mind.

 

[oscar21]

Click grid pro is by far the easiest one I've fitted. Schneider by far the worst