Why Have I got a Switch Fuse Isolator in my Meter Box

What’s Inside your meter box? Understanding the equipment in your meter box is very important and what it is used for. When consumer units are located over 3 metres away from the mains intake position you will have to install a switches fused isolator.

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[AndyK.]

Rule of thumb, tails over 3m need fusing. (some DNO say 2m? I think)

[markrussell]

My in-laws have 3 C.U's in their property. Two adjacent the meter & cut out & another located some 30 or so metres away at the other end of the property. The original 'electrician' fed that distant C.U from Henley blocks off the meter tails via a 16mm 6242Y T&E. The only thing protecting it was the 100A DNO cutout fuse! No additional main earth conductor was run either. Just relied on the 6mm CPC of the 16mm twin which was connected directly into the earth terminal of the cable head/cutout.
I had a horrible sinking feeling when I discovered it. Needless to say it's now been rectified. The whole house is wired in a rather unorthodox way to be fair.

[protectiongeek]

I started work as a trainee distribution engineer with SSEB in 1986 and the 3m rule was already well established. Why 3m? It was/is viewed as a practical length for the meter tails to the DB or main-switch. The DNO don't want to be responsible for protecting any more of a customer's installation than is reasonable practicable. Over the years I have seen some 'interesting' interpretations of what constitutes 'within 3m', including an installation where the meter was indeed within 3m of the main-switch if you measured with a tape measure _across_ the room. The 'electrical length' (tails clipped up the wall from the meter, across the ceiling and down the opposite wall to the switchgear) was closer to 9m. Nice try.

[andysims]

A friend has just moved into a property built about 6 years ago. Guess what the tails are appropriately 6M long and no SW Fuse isolator. Don’t you just love House Bashers

[sergiofernandez]

What decade did Gordon.R fit that meter? Nice to see a GRP main cut out with seals to boot.

[avfczoff]

Should the extended meter tails have RCD protection? Maybe a time delayed S type RCD 100mA?

[d]

What is the fuse? Does it need to be the same as the main fuse or lower rating?

[lnp]

Can i just pull out the main fuse to change my electric meter in my home, or do i need to unscrew it ?
Obviously i will kill all power in my house but im on about the electrical main live black cable that comes into my house.
Any feedback would be much appreciated

[davidrogers]

Do you not need to Earth the Fused Main Switch. ?

[Spence-xidb]

Say it’s 100a cut out do u have to use selectivity for the second fuse so say 80a?

[guffermeister]

A suggestion for you or efixx team - why is the 3M rule in place? What are the calculation for the down rating or is the 3M just a rule without say current limitations and just a number picked from someones head much like the 2.5M sockets in a bathroom rule?

[TeamSimpsonRacing]

Meter tails buried in the fabric of the building! Doubt there is additional earth mechanical protection, so this is potentially dangerous

[therealdojj]

when they fitted my smart meter they removed the isolator switch, should i get one fitted again or is this one of those things thats designed to stop unqualified types from adding a plug?
thanks

[AndyK.]

That's not an "old" meter lol