16mm tails with 100amp fuse?

[nikinoo70]

I am going to be changing the consumer unit in a house. The owner arranged to have an isolator switch fitted by N power (free of charge). Ive been to look at it and the guy has fitted it with 16mm tails. The customer was told that this was because the tails to the ccu are 16mm. But it has a 100amp fuse. I will be fitting a new 9.5kw shower and the cooker is electric as well as the usual ring main and lights ect. It is a 3 bed house. I was going to change the tails to the ccu to 25mm.

Am I correct in thinking that he should have fitted 25mm to the isolator switch? All the tables ive looked at say I am.

 

[somersetsparks]

Is it actually a 100a Fuse? or does it just say that on the carrier, we only ever put a 60 or 80 in if it has 16mm tails when we change meters. Chances are its 60 or 80, It is on there side anyway so I wouldn't worry to much

 

[Amp David]

Main fuse may not be 100 amp, it may be marked as but may be less.

Just install your 25mm tail into the CU then you'll be able to sleep at night.

 

[i=p/u]

I asked this the other day..

Just cause it says 100a, does it mean it is, ...... How can you check this,,, can you open the carrier?

 

[nikinoo70]

the cables are 25mm betwean the fuse and the meter and 16mm from meter to switch. seems strange to me

 

[i=p/u]

must be 80A fuse then

 

[somersetsparks]

Or 60A? Nice thing is with the isolator, it isnt your problem its their installation and they have put 16mm tails in, I would put 25mm to the fuseboard and be done with it

 

[i=p/u]

somersetspark how can you check fuse size in carrier?????????

 

[somersetsparks]

I work for DNO mate so have mocopa. However as I have said past that isolater is not your problem, its theirs.

 

[i=p/u]

no no no, im working on a house myself and the carrier says 100A and they looking to add another shower, but im thinking maybe isnt 100A in carrier..

whats mocopa?

 

[i=p/u]

i see its a training thing.. mocopa

 

[somersetsparks]

If you look at the fuses tripping times then I think you will find they will blow at 1.5x in an hour so even a 60A would take 90 for an hour, I wouldn't honestly worry to much. If you were in western powers area, they only give out 80A's apart from special requests, other DNO's do either 60A or 100A.

 

[i=p/u]

nice info which i know but couldnt apply it or am i just lazy.. ty..

is there no way of checking tho....

is their a diffwerent in resistance if you measure between prongs

 

[somersetsparks]

Nope, no way other then a physical check I'm afraid, so is a bona fide limitation!
Bear in mind if you are working in a flat and come accross a bright red fuse and carrier, this is a solid link! The fuse will be down at the incoming position to the building!

 

[Swicade]

I tend to install 25mm tails on board changes these days as a matter of course tbh....always the possibility someone will request an upgrade to 100A in the future so at least it's sat ready waiting for it.

 

[Geoffsd]

Is that not using 50% more copper than necessary?

 

[Rauer]

Just pull the carrier and have a look

 

[JD Hogg]

Has anyone ever asked the DNO to downgrade the main fuse from 100A to 60A or 80A? If so did they do it?

 

[Rauer]

The DNO fuse as far as I am aware is to protect THEIR tails to the meter not OUR tails from the meter!

 

[i=p/u]

maybe but i would of thought fuse at their green box, so was for consummer, byt this is a good guess