100a Switched Fuse?

[munch88]

Hi there,

I am carrying out a rewire and putting a new metal consumer unit under the stairs.

The customer wants the original position of the consumer unit to be moved but will still be under the stairs.

The distance away from the meter will be 4m and will run under the floorboards for approx. 2 meters
Therefore I am going to use 25mm 3 core SWA.

I believe I require a 100a switched fuse due to the length of the cable exceeding 3 meters.

Can anyone suggest a decent and reasonable prices 100a metal switched fuse which will be easy to terminate an SWA.

Thanks

 

[Octopus]

Why do you think you need a 100A switch fuse? What is the DNO fuse?

 

[telectrix]

why SWA if it's not buried in wall< 2" deep?

 

[munch88]

I was led to believe that tails exceeding 3 meters required a switched fuse as the DNO only protect tails up to 3 metres. I'm happy to be proved wrong as it's cheaper and less hassle

Also, the use of SWA was just to give the cable some extra protection under the floor. Also would look neater cleated up the wall and terminated via gland rather than knock outs.

 

[Spoon]

What about Murdoch's two questions "Why do you think you need a 100A switch fuse? What is the DNO fuse?"

 

[munch88]

What about Murdoch's two questions "Why do you think you need a 100A switch fuse? What is the DNO fuse?"

The DNOs fuse only protects tails up to 3 meters (so I believe) and if an additional fuse is required to protect tails exceeding 3 metres then surely it's better to fit a switched fuse so isolation in the future can be achieved without pulling the DNO fuse.

 

[Richard Burns]

Not such a bad plan as it goes, as indicated the fuse should be less than or equal to the DNO fuse, to try and hope yours may go first, if it ever comes to that.
A metal clad 100A switch fuse is probably your cheapest option something like this.

 

[Spoon]

Maybe my post should have been more clear, sorry.
No one was questioning your plan to use a switched fuse. A couple of us were wondering why you choose 100A and wanted to know what size is the DNO fuse.
I thought the fuse had to be smaller than the DNO fuse Richard? Do you not use discrimination in this case?

 

[munch88]

Maybe my post should have been more clear, sorry.
No one was questioning your plan to use a switched fuse. A couple of us were wondering why you choose 100A and wanted to know what size is the DNO fuse.
I thought the fuse had to be smaller than the DNO fuse Richard? Do you not use discrimination in this case?

The DNO is 100A so therefore was going to use 100A or even could use 80A (should of stated that in my OP)

I will check with the DNO whether I definately require an additional fuse due to the length.

 

[Midwest]

I would not recommend the one Richard suggested I'm afraid. It's a bit psychically small, especially terminating 25mm swa. Try something like Wylex 110M 100 Amp SPN Metalclad Switchfuse - Edwardes , you can get them most wholesalers. Install it before 1st Jan 16 though, cos its got a plastic cover :builder:. You can get one with an 80amp fuse or a 60amp.

OSG suggest meter tails should be minimum 25mm and that the DNO may specify maximum length and may require an isolator fitted (2.2.3 green OSG). And where their cut out provides fault protection for the tails, they may require certain method of installation. Where buried in walls further protection may be needed. Reg 434.2.1 & 434.3 (iv) and others :juggle2:

You would have to installed some sort of metal box to terminate the swa, next to the meter, so using a switch fuse is ideal. So I concur with you munch88, except you should use an 80amp fuse if the DNO one is 100amp.

You could run it pass the DNO. In my experience, they would be happy with what you are proposing.