Single Phase or Three Phase – Service Fuses

Single phase sites have one ‘service fuse’ and three phase site have three.

A service fuse is a large black rectangular fuse. They’re generally quite easy to spot at your main switch board or meter board. 

Three phase power supply and electricity meter

Household with a three phase supply. Note the 3 x service fuses at the top left of the board. Single phase sites have only one of these.

Single Phase or Three Phase РMain Switch

Another way to identify three phase from single phase is the width of the main switch. Single phase switches are ‘one pole’ wide, whereas three phase switches are ‘three poles’ wide. See the picture below for what I mean.

Electricity Main Switch

Single phase / single pole main switch (on left) vs. three phase / three pole main switch (on right).

These ‘Main Switches’ are usually found at your meter board. In larger premises or unit blocks you can also find main switches at each sub board or distribution board. 

What About Two Phase Power?

Two phase power supplies are actually also quite common in Australia. Two phase power is best identified using the ‘Service Fuse’ method outlined above. There will be two service fuses present for two phase, rather than one or three.