60A Main fuse & NIC assesment?

[malcolmsanford]

usually want you to put a KMF (with an 80A fuse) in if the tails are over 2 or 3 metres long. for some reason.

The reason is that the DNO are quite happy for you not to fit a protection device after the meter on your tails, as there fuse will afford it protection. Anything over 3-5 mteres depending on the DNO, they will not provide that protection and so you need to fit a protection device, normally a BS 1361 fuse.

 

[nick611]

if the installation includes an electric shower he would be advised to ask for an upgrade. i believe this is mentioned in one of the old electricians guides

 

[CRAIGNEWHAM]

Nick, he has a gas boiler and a gas cooker, so unlikely he'll ever need to upgrade.
But, in theory, will the fuse go before the main switch trips?

 

[malcolmsanford]

Craig the main switch is just that a switch it is not a protection device, the only time it is ever likely to fail is mechanically overloaded and it will weld closed.

Think of it as a light switch, the light switch will not go before the protection device as that is not what it does.

 

[nick611]

it seems many people confuse the current rating of main sw,s and rcd,s with a tripping current. as malcolmsanford says the rating is just how much current it can handle without melting. this is a very common if a little worrying mistake. a main sw or rcd will not dissconect under overload it will just melt. your main sw is rated higher than your cutout fuse so you will be fine

 

[CRAIGNEWHAM]

Thanks Nick,Malcolm