Fused isolator switches?

[D4dog]

Hi all, quick question. A friend is doing up his house, and was advised by his sparky that they couldnt do any work on the electrics until a fused isolator switch was fitted between meter and CU. I suggested it simply needed to be an isolator switch, as tge fuse would serve no purpose (I have exactly that in my own property). However, his sparks was adamant about this as being a requirement.
I cannot see this requirement in part p...can anyone enlighten me as to:
Is it a regulatory requirement?
What does the fuse protect given that the cu has its own main breaker?

Thanks.

 

[ebee]

If the existing set up is tails directly from the meter to the consumer unit then it is extremely unlikely that a fuse would be required.
First of all the Electricity supplier determines what length of tails is allowed to be protected by the cut-out, so unless this is exceeded then no another fuse would not be required.
If additional tails are added to, for instance, a second consumer unit etc then a fuse might be required.
But, unless you adding length (or reducing tail size cross sectional area) to an already compliant set up then no another fuse is not required.
There will often be no determent to adding one though except, perhaps, the cost.

 

[Murdochcat]

The DNO guidelines are if the cable distance between the service head and the fuseboard / consumer unit is OVER 3 meters then a switch fuse is required ....

 

[jurassic sparkk]

The DNO can sometimes provide a main isolator for free, it really depends. You can always phone them up and enquire about it.
It is better to install one, as in the future it makes changing tails, consumer units etc easier.

 

[D4dog]

Thanks...wasnt aware of the 3m guidance, which explains perhaps why me setup only has an isolator, not a fused one. I will advise him accordingly!

 

[EFLImpudence]

The DNO guidelines are if the cable distance between the service head and the fuseboard / consumer unit is OVER 3 meters then a switch fuse is required ....

Yes, but is there a valid reason for that or is it a misreading of a regulation?

I.e. the tails are over three meters so you must install a fuse the same rating as ours.

 

[Murdochcat]

Yes, but is there a valid reason for that or is it a misreading of a regulation?

I.e. the tails are over three meters so you must install a fuse the same rating as ours.

What is your interpretation of the DNO guidelines?

 

[EFLImpudence]

I think it might be similar to people who misread 433.2.2

"433.2.2
The device protecting a conductor against overload may be installed along the run of that conductor
if the part of the run between the point where a change occurs (in cross-sectional area, method of installation, type
of cable or conductor, or in environmental conditions) and the position of the protective device has neither branch
circuits nor outlets for connection of current-using equipment and fulfils at least one of the following conditions:

(i) It is protected against fault current in accordance with the requirements stated in Section 434
(ii) Its length does not exceed 3 m, it is installed in such a manner as to reduce the risk of fault to a minimum,
and it is installed in such a manner as to reduce to a minimum the risk of fire or danger to persons (see also
Regulation 434.2.1)."

 

[Murdochcat]

The DNO can sometimes provide a main isolator for free, it really depends. You can always phone them up and enquire about it.
It is better to install one, as in the future it makes changing tails, consumer units etc easier.

That is an isolator, not a fused isolator