Tommy Mac Discussions › Forums › Fix-it Forum: Home Improvement & Do It Yourself Repair Forum › Do GFCI breakers need a ground wire? › Replacing groundless outlets with GFCI’s
The NEC, section 210-7(d), and CEC, section 26-700(9), are quite explicit that GFCIs are a legal substitute for a grounded outlet in an existing installation where there is no ground available in
the outlet box. But your local codes may vary. As for the TEST button — there’s a resistor connecting the LOAD side of the hot wire to the LINE side of the neutral wire when you press the TEST button. Current through this resistor shows up as an imbalance, and trips the GFCI. This is a simple, passive, and reliable test, and doesn’t require a real ground to work. If your GFCI does not trip when you press the TEST button, it is very probably defective or miswired. Again:
if the test button doesn’t work, something’s broken, and potentially dangerous. The problem should be corrected immediately.
The instructions that come with some GFCIs specify that the ground wire must be connected. We do not know why they say this. The
causes may be as mundane as an old instruction sheet, or with the formalities of UL or CSA listing — perhaps the device was never tested without the ground wire being connected. On the other hand, UL or CSA approval should only have been granted if the device behaves properly in *all* listed applications, including ungrounded
outlet replacement. (One of us called Leviton; their GFCIs are labeled for installation on grounded circuits only. The technician was surprised to see that; he agreed that the NEC does not require it, and promised to investigate.)