consumer unit rating

[teracir]

guys,

can someone please specify what the effects would be for installing a CU with 100A isolator when the main supply (electricity company cutout) fuse is only 60A.

cheers

 

[RF Lighting]

Depends how much load you have running off the CU

 

[markthebuilder]

if you need a 100amp isolator because the calculated design load (allowing for diversity) ruining from the cu requires it then theoretically when running on full load your main fuse would blow and you need to speak to your distributor about having a bigger one fitted.

If however you are a domestic customer who has standard 100amp main switch because that is the size fitted to the CU then no problem.
basically you wont overload in normal use and overload protection to individual circuits is provided by the individual mcbs

 

[teracir]

thanks for replys guys,

my question was based on the fact that it is becoming increasingly difficult to find consumer unitas with a 60A isolator (unles you buy a 2-3 way unit which is useless) so what would happen if a unit with 100A isolator is installed?

i understad that each circuit will be protected by its own fuse and hence the isolator will trip if there is a fault on that particular circuit. so if a 100A isolator is used and as long as the load is not 100A (otherwise the electrtcity supply fuse would blow since it is rated at 60A) then it should be alright.

 

[dingbat]

Teracir, the 100A is the load that the isolator can safely switch, should you have to shut down the installation under load. In a domestic installation this should only ever happen in an emergency.

The isolator is not an overcurrent device and will not trip. It is just a manual switch. Its rating will have no effect whatsoever on the operation of either the main fuse or any of the circuit protective devices.