Kitchen re wire

[Lavenderminx]

Be gentle, this is my first time on a forum.

Anyway, having new kitchen fitted and wanted to update the wiring (Scots regs))......... was going to run 4mm radial (32MCB) t&e cable to a 4 gang grid for(fridge/freezer/dish washer/washing machine) then from the 20 amp DP grid switch run to each appliance a single cable (no more than 2meters in length each) ending in a non switched single gang socket (all aplliances have fused plugs) Can I drop from 4mm to 2.5 from 20amp DP switch to socket?or does it have to stay 4mm?

The rest of the kitchen is on a 2.5 mm (32MCB) t&e ring with a number of double gang sockets (5 in total). On this ring I have a second grid (3gang) Microwave, extractor, undercounter lights) all 2.5mm cables as this size cable is easier to wire. Again all fused plugs so due to the 20amp DP switch am I right in thinking i don't need a FCU, just a single gang non switched socket?

Large double oven/hob is on 10mm dedicated radial.

How does that sound? Will have it all PIR tested, but wanted to check before I go ahead.

 

[flameport]

Circuits should be wired in the same cable size throughout - although smaller sizes at the end could be permitted and would actually be useful in some instances, a domestic kitchen isn't one of them.

While what you have described is possible, it certainly isn't what I would do.

Grid switches serve no purpose other than adding cost and additional points of failure. Will also be rather difficult to fit 4mm cables into the back of them.
They are also ideal for accidentally turing the fridge or freezer off and destroying the contents within. Particularly when the switches are located above a worktop, and items such as a microwave or toaster get shoved against the switches.
A grid with multiple switches on a ring will cause a high load in a single location, the very thing which should be avoided.

Unless this kitchen has an unusually large number of appliances, two 20A radial circuits would be fine. Or a single 32A ring instead for those that insist on such nasty designs.
20A or other switches are not required - appliances plug in, and in the rare instances that isolation is required, it is achieved by removing the plug from the socket.

10mm radial for the cooker is probably oversized, unless the circuit is excessively long or there are other derating factors.

 

[stillp]

Will have it all PIR tested

??????
Passive Infra Red?

 

[PrenticeBoyofDerry]

Can I drop from 4mm to 2.5 from 20amp DP switch to socket?or does it have to stay 4mm?

You could only decrease cable section, if you down fuse 20A DP switch will not down fuse. It is an isolator rating not a circuit protective device.
So your proposed design has not been thought out well.

Large double oven/hob is on 10mm dedicated radial.

Is that the cable size that it requires, in a domestic property 32A can deal with a cooking appliance up 15kW.
Some homework and calcs on output, diversity, voltage drop and ref methods would be very helpful on cable sizing

How does that sound?

Not well thought through!

Will have it all PIR tested, but wanted to check before I go ahead.

If it is a new installation (ie new circuits) an electrical installation certificate rather than an EICR/PIR would be required.