An Observation

[MICKYG]

Hi all

I have noticed that newer houses have 20 amp circuit breakers on the power circuits and usually 10 power points. The stove circuits have 32 amp breakers.

Older houses seem to have 10 amp fuse wire arrangements. This is a little confusing to and old bloke. Any one care to explain the changes over the years.? I am aware that the wiring size changed but not sure when ?

Regards Mike

[Barry_White]

In the 1976 AS3000 allowed for some changes and on 2.5mm2 cable they actually allowed 30 amp circuit breakers but they revised that in 1981 because they found that 30 amp breakers were too high and the changed it to 20 amp breakers. They have sinced changed to RCD breakers on all circuits but a maximum of 20amps on a power circuit.

The number of points on a circuit varies with the number of circuits in the installation. As low as 7 on a single circuit and up to 25 points per circuit on multiple circuits and all points must be spread evenly over all circuits.

On stove circuits etc. all is dependant on the current draw by the appliance on what size cable is used with the matching circuit breaker to the cable.

[Schtoo]

Pretty simple really.

A rewireable fuse isn't a very good circuit protection device, so it's downrated to 16A to protect the cable. The fuse may pop at anywhere from say 10-20A.

A circuit breaker, by comparison is pretty accurate so it can go the full 20A on the exact same circuit. The breaker will trip at say 19-21A.

A HRC fuse (cartridge) is very accurate, and is rated the same a s breaker. It will trip at what it says on the label, in the case of your power points, 20A.

And that's it folks.

Got nothing to do with cable size, the number or points, type of installation or any such stuff. The fuse/breaker has one job, and one job only. Protect the wiring.


As for the 10 outlets per circuit, just a common sense thing. Lots of things plug in, it's easy to overload the circuit. Add in more outlets, add in more circuits. Old houses had fewer outlets, fewer plug in appliances and hence forth fewer circuits were needed.

Hope that helps.

[MICKYG]

Thanks Barry and Schtoo,

This helps one to understand some of the differences in the supply of power and the necessary equipment to comply with new code.


Regards Mike.