1.5mm for grid system radial

[curly]

Hi guys later on in the week I'm doing a kitchen up with my tradesman. We are installing a grid system with 16amp radial's for the appliances, they are all on a 13amp plugs, and the cables will be clipped direct (in the kitchen they will be sunk into the wall and plastered over.) There is no insulation in the loft.

I done a grid system a few months ago but it was run in 2.5 so my question to my tradesman was can we do it on 1.5 as space in the grid box is tight. He told me to do my own calculations and report back

As far as I can tell 1.5 is rated at 20amps and there is no derating factor, the cable length will be less that 15m voltage drop is not an issue.

Have I missed anything or am I good to go ?

Thanks

 

[Pete999]

Hi guys later on in the week I'm doing a kitchen up with my tradesman. We are installing a grid system with 16amp radial's for the appliances, they are all on a 13amp plugs, and the cables will be clipped direct (in the kitchen they will be sunk into the wall and plastered over.) There is no insulation in the loft.

I done a grid system a few months ago but it was run in 2.5 so my question to my tradesman was can we do it on 1.5 as space in the grid box is tight. He told me to do my own calculations and report back

As far as I can tell 1.5 is rated at 20amps and there is no derating factor, the cable length will be less that 15m voltage drop is not an issue.

Have I missed anything or am I good to go ?

Thanks

Hi curly, what exactly do you mean by a grid system?

 

[Ian1981]

I’m guessing a grid switch with DP switches feeding socket outlets for appliances each grid switch on its own radial circuit via 16amp OCPD.

 

[telectrix]

what's the total load of the appliances connected to the grid switches. 1.5mm cable supply to the grid will just about handle 2 appliances ( e.g. 1 washing machine + 1 tumble dryer).

 

[Rosco]

Instead of looking at the cable size have you thought of any other alternatives to parts of the installation that may make your life easier when doing grid switch’s for appliances?

 

[curly]

this system with double pole switches

 

[curly]

what's the total load of the appliances connected to the grid switches. 1.5mm cable supply to the grid will just about handle 2 appliances ( e.g. 1 washing machine + 1 tumble dryer).

My tradesman wants each one on its own circuit.

Instead of looking at the cable size have you thought of any other alternatives to parts of the installation that may make your life easier when doing grid switch’s for appliances?

Nope I can't think of any do you have any suggestions

 

[telectrix]

4 grid switches. each capable of 20A. you need to supply with either
1. a 32A RFC using 2.5mm cable, or:
2. a 4mm radial.

a 1.5mm radial is a non-starter unless you have a direct line to the local Fire brigade.

 

[telectrix]

My tradesman wants each one on its own circuit.

they can't each be on their own circuit unless you run 4 x separate cables, each on their own OCPD. one to each grid switch.

 

[curly]

4 grid switches. each capable of 20A. you need to supply with either
1. a 32A RFC using 2.5mm cable, or:
2. a 4mm radial.

a 1.5mm radial is a non-starter unless you have a direct line to the local Fire brigade.

The switches are rated at 20amps and the cable is protected by 16amp MCB I think you have misunderstood. each appliance will be on its own circuit with its own 1.5 cable.

they can't each be on their own circuit unless you run 4 x separate cables, each on their own OCPD. one to each grid switch.

What's an ocpd

We will be running 4 1.5 or 2.5 from the board each on there own MCB to the 20amp double pole switch then to a 13 amp 1 gang unswitched socket.

 

[telectrix]

understood there. your OP was not so clear. OCPD... overcurrent protective device e.g. fuse/MCB. so you plan on running 4 separate radials to the grid, each to 1 x 20A D/P switch for each appliance?

 

[davesparks]

they can't each be on their own circuit unless you run 4 x separate cables, each on their own OCPD. one to each grid switch.

Which is exactly what the OP says he is doing

 

[telectrix]

Which is exactly what the OP says he is doing

but his OP was not so clear that he was running separate radials from CU to grid.
We are installing a grid system with 16amp radial's for the appliances,

 

[Rosco]

Nope I can't think of any do you have any suggestions

Your situation as I understand it is to make 2nd fixing easier by way of reducing cable size, there are other options available like firstly using a deeper back box and to take your time dressing the cables tidy in the box which will make connecting and screwing back so much easier it will take time but well worth it and speed will come with practice.

 

[curly]

but his OP was not so clear that he was running separate radials from CU to grid.
We are installing a grid system with 16amp radial's for the appliances,

I do apologize i will try to be clearer the next time. I do plan on running 4 cables. One for each appliance

Your situation as I understand it is to make 2nd fixing easier by way of reducing cable size, there are other options available like firstly using a deeper back box and to take your time dressing the cables tidy in the box which will make connecting and screwing back so much easier it will take time but well worth it and speed will come with practice.

Yes it's to make second fix easier.
To be honest it's an 8 grid switch with a 47mm back box there are 6 Appliances,
1Oven
2Gas ignition
3Extractor above hob
4Dishwasher
5Fridge freezer
6Extractor fan
7Downlights
8Led strip lights under wall units

The last time I did one I took my time, It was difficult to get the switches in place with the amount of wires that were there, but like you say practice will help

However can any one confirm that I have done my calculations correct and 1.5mm is indeed acceptable?