If you have a home that is wired with only two wires to each of your outlets never fear there are ways to make it safe and legal. Just having two wires does not mean that your house was necessarily wired by someone doing substandard work or having a great disregard for human safety.
Older houses were wired with two wire circuits before an enforcement of the electric code became a requirement. It was also back in these times that electricity was not totally understood by all which is why the two wire outlets were manufactured to begin with.
It only takes the two wires to bring electricity to your appliances and have them work correctly. The problem is safety. That is right. The third wire is a safety device built into your electrical system. The third wire which is referred to as a ground or equipment ground is designed to provide an effective path to "earth" to help prevent electrocution hazards should an appliance or its wiring fail.
Many people think that adding the little three prong adapters to an outlet adequately compensates for the third prong on the plug. This does nothing more than to let you plug the appliance into the outlet. Even if you remove the screw and screw it in place with the screw holding the outlet plate on the outlet. The reason this is not adequate is because you still do not have a wire going to a good earth ground from the box. Do not worry as there are safe methods to repairing this situation without having to rewire your whole house.
Keep in mind if you are installing new wiring you must use three wire cable that has a ground wire in it. This is required by the electrical code and is enforced by the state and city or county building inspectors.
If you have the two wire outlets in your home and have had to replace them you know that you can not buy them anymore and you must buy three wire outlets. You cannot legally install these outlets on a two wire system unless you do one of the following.
1. You can install the new outlets and mark them as "NO GROUND". This will let everyone who uses the outlet know there is no ground. This is legal in most places and was legal with the adoption of the 2002 National Electric Code.
2. You can install these outlets safely and legally if you remove the first outlet in the circuit (The
one closest to the panel box) and replace it with a Ground Fault Circuit Interrupter"(GFCI). By using this GFCI outlet you will provide a way for the circuit to trip if any power is lost through the appliance. This can be annoying though if you use any type of appliance that produces heat such as space heaters or toaster ovens. The GFCI actually measures the amount of current going to your appliance and compares it to the amount of current coming out of your appliance on the neutral wire. If there is a difference the GFCI will trip and cut out the power on the circuit.
3. The other alternative is to install a ground wire into each box on your circuits and tie them together as per code requirements and taking this wire all the way back to your panel box. Once you get the ground to the panel box you have then completed a path to your "earth ground" since your panel box has to be grounded. If it is not grounded then you have some real problems.
Remember quick fixes are no more safe than the two wire outlets you have to start with. I strongly suggest if you do not want or cannot have your home rewired at least install the GFCI outlets. If you have to use something that will cause nuisance tripping of a GFCI then install some new circuits using three wire cable to accommodate the outlets supplying those appliances.