Testing for neutral-to-ground connections in new construction

A study was performed to seek out inadvertent connections between neutral and ground in the power distribution system of a newly constructed hospital, prior to occupancy. Such connections are not only violations of code but could cause medical device problems. Ground wires are not intended to carry load currents except during faults. When currents do flow in grounds, medical device chassis voltages are elevated and some devices may respond unpredictably. Suitable acceptance testing is not commonly done. In this study, a simple test method was developed that helped reveal and correct many neutral-ground misconnections. The authors advocate incorporating such a test into building construction contract specifications.