My home has three prong ungrounded electrical receptacles, what should I do?
The house was built with cloth Romex wire, a 2 wire system that did not have a grounding wire. This is typical in older houses. The grounding circuit in a three-wire system adds an additional layer of protection. It is not so much that a two-wire system is unsafe, it’s that a three wires system is safer. The grounding circuit creates a parallel (alternative) path to ground which helps protect people from electrical shock and helps protect higher end electrical equipment from external voltage spikes like those that may accrue from a lighting strike or a heavy static charge.
When three prong receptacles with open grounds are identified and a two-wire system is present, the NEC currently allows the following methods to be used to resolve the problem:
- Install an equipment ground. (recommended for high end equipment, see previous comments). This requires running new wire or electrical cables and can be expensive and not always practical.
- Provide GFCI protection for the receptacle (either at the receptacle or upstream of the receptacle). The receptacles are to be marked no equipment ground. This method does not provide an equipment ground, so people are protected but sensitive electrical equipment is not.
- Replace the existing three-hole receptacle with a two-hole non-grounded receptacle. This would be the least preferable method since neither people or equipment are protected.