From the little knowledge I have of Canadian installations circuit breakers have a magetic and thermal trip. Disconnection times can alsoe be achieved by the use of a RCD/GFCI where ground loop impedance is too high to achieve disconnection in the required time.
I have found the following in the CEC 10-500:
“The path to ground from circuits, equipment, or conductor enclosures shall be permanent and continuous, shall have ampacity to conduct safely any currents liable to be imposed on it, and shall have impedance sufficiently low to limit the voltage above ground and to facilitate the operation of the overcurrent devices in the circuit.”
And in the CEC Handbook guidance it states that this is normally achieved by a sufficiently low impedance such that the overcurrent device is presented with a fault current of 5 times it’s rating. Which in effect is the 0.4 second requirement of BS 7671.
What I would like to know is does anybody bother working this out in Canada? Are GFCIs routinely used on circuits?
Last edited by Stuart_Urban; 10/08/13 05:24 AM.