Tip Sheet 7: Safety switches and circuit breakers

It’s important to note the difference between a safety switch, ordinary fuses and circuit breakers.

Safety switches are designed to protect you and your family against electrocution from Active to Earth faults, which are the most common form of electricity fatality. They are not a simple fuse or circuit breaker.

Fuses and circuit breakers are designed to prevent electrical circuits from overloading. They protect property, not people. Fuses and circuit breakers do not provide adequate protection against electric shock because the amount of current which will injure or kill a normal adult is so small that they may not detect the problem until the damage is done.

The severity of an electric shock is determined mainly by the amount of current flowing through the body and the time the current flows before it is cut off.

A safety switch cuts off the power supply when the current to Earth exceeds 30 thousandths of an ampere, a miniscule amount when you consider that many power tools, portable heaters, and so on use up to 10 amperes.

How quickly is the current cut off?

Within 30 thousandths of a second, about a thirtieth of the time taken for a single heart beat, or the click of your fingers! That’s pretty quick.

There’s another way a safety switch can give you peace of mind: many horrific fires, caused by poorly fitted or degraded wiring, could have been prevented by one. If you decide to install a safety switch, also consider upgrading your porcelain fuses with modern efficient circuit breakers.

In fact, this would be a good time to do away with your old switchboard and fuses and replace it with a new moulded switchboard, to house your safety switch and circuit breakers.

> What to do if your safety switch trips…