60A main fuse 100A breaker?

[vsynth]

I was looking at getting the shed wired up...yes I know old topic lol anyway I notice that the main incoming fuse before the meter is 60A but the main breaker in the CU is 100A.

I'm not too hot on discrimination calcs (I'm and electrician but don't do installation work) but I'm guessing that this is wrong?

[Edit] or is the breaker OK because downstream (inside the CU) can take 100A and the incoming cable is protected by the 60a fuse which is OK?

 

[Adam_151]

The main switch is just that... just a switch, not a breaker, so forget all about discrimination

As long as the switch is equal to or greater than the rating of the company fuse, then jobs a carrot (though its unusal to fit a board with a switch of less than 100A these days*, remember also that the DNO might upgrade their fuse)


*though one buget make sells cheap 12 way boards with 80A main switches

 

[Spark123]

The main breaker as you refer is most likely only an isolator switch, the rating of the contacts in it are rated at 100A. It will not switch off it you exceed 100A.

 

[vsynth]

Thanks, that makes sense

 

[djrichie_t]

give the electricity company a call, tell them you only got a 60 amp cut-out fuse and they will upgrade it for you free of charge.

 

[Katron]

Just a quick one, in the middle of a job, an outside light on it's own circuit...problem is that the main incoming fuse is 100amp and the fuse board is an old wylex 3036 rated at 60 amp, maximum demand to be 70A, advised customer to replace board and tails, but has refused.

Should I carry on with the work and write my findings on cert or stop work and cut my loses?

 

[djrichie_t]

Some people would do the cert and make a note to cover their backs, however I personally would stop work and insist on an upgrade, as those wylex units are not at all tolerant with any excess load whatsoever, they do start to melt quite easily.

Last thing you want is a fire on your hands.

 

[vsynth]

Just a quick one, in the middle of a job, an outside light on it's own circuit...problem is that the main incoming fuse is 100amp and the fuse board is an old wylex 3036 rated at 60 amp, maximum demand to be 70A, advised customer to replace board and tails, but has refused.

Should I carry on with the work and write my findings on cert or stop work and cut my loses?

70A, have you applied any diversity factors?

If it is maxed out then explain to the customer that you can't continue and will charge them for the work done so far and leave the installation in a safe condition.

 

[Katron]

yes have applied diversity, will explain to customer again,

Thanks for the quick response!!!!

 

[Deleted member 54734]

give the electricity company a call, tell them you only got a 60 amp cut-out fuse and they will upgrade it for you free of charge.

Is that right?

 

[djrichie_t]

Yep - used to work for the electricity board, they will happily upgrade at customers request.

 

[Spark123]

Just a quick one, in the middle of a job, an outside light on it's own circuit...problem is that the main incoming fuse is 100amp and the fuse board is an old wylex 3036 rated at 60 amp, maximum demand to be 70A, advised customer to replace board and tails, but has refused.

Should I carry on with the work and write my findings on cert or stop work and cut my loses?

If you are adding to a circuit on a board which is already overloaded then I'd imagine you'd be falling foul of regulation 130-07-01:

"No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, which will have to carry any additional load is adequate for the altered circumstances and the earthing and bonding arrangements are also adequate."

Btw, how do you know the supply is 100A?

 

[Katron]

removed intake fuse and looked....
I know you shouldn't but you need to know for when filling out an EIC anyway..and leccy board aren't helpful...
Seen quite a few intakes saying on fuse holder 100A when 60A insde and vice versa.