Rewiring That Old House for Grounded Outlets
Part 8 of 8 in The Old House Web Home Hazards Series
If you are remodeling an older home, you may notice that the electrical outlets look a bit different than the ones in newer homes, with only two slots in the outlet. That's because they aren't grounded. So what does that mean, and why is grounding a good thing? The ground wire in newer wiring was added to prevent electrical shock, for instance in the case of a loose wire in an appliance. Current from that loose wire will flow through the ground wire, not through you when you touch the appliance.
Do I Have to Rewire My Older Home?
Building codes in most localities do not require you to upgrade to grounded wiring. However, it is a very good idea to do so; but if you do, then local codes and national electrical codes apply.
What is Involved in Adding Grounds?
That depends on how your house is currently wired. You can run a ground wire from your main electrical box if you have access (for instance, if you are replacing all the wallboard or lath and plaster). Or you might get lucky and find that your house was wired with armored cable. If so, you can use the outer metal sheath to ground your outlets.
Is There an Easier Way?
If you don't have armored cable or access to the wiring, your best bet is to use ground fault interruptor (GFI) outlets. The way the GFI works is that it detects an unbalanced load (like a loose wire) and shuts down all current flow through the circuit. Determine the first outlet from the main electrical box in each circuit, and then replace it with a GFI outlet. You can then replace the rest of the outlets in that circuit with standard grounded outlets. These outlets must be connected to the load side of the GFI outlet, and should all be labeled to note that they are GFI protected. One caution: surge protectors will not work on a GFI protected outlet.
Before you start, make sure you only work on dead circuits, where the power has been disconnected at the breaker panel or fuse box. Familiarize yourself with all applicable building codes, and determine whether permits and inspections are required in your locality. And if you don't feel comfortable working with wiring, by all means hire a licensed electrician.