A Ufer ground (invented by Herb Ufer in the 1950's) consists of metal bars that are encased in concrete and buried a few feet underground. Approved by the NEC as a "Concrete Encased Electrode," a Ufer grounding system has an advantage in soils where rock or other barriers prevent deeply driving a single ground rod. If properly sized, the large mass of concrete can achieve an acceptable earth ground impedance even when buried only a few feet deep.
What is the difference between a ring ground and a halo ground?
A ring ground consists of minimum #2 AWG bare wire buried a minimum of 30" in the soil encircling a structure. A ring ground is one of the allowed NEC alternatives to a single driven ground rod. A halo ground consists of bare or insulated wire run around the inside ceiling of a structure or equipment room and is typically bonded to the corners of a buried ring ground. The halo ground acts as a shield for reducing radio frequency interference (RFI) from electromagnetic fields.
What is an isolated ground?
With an isolated ground, a separate, insulated safety ground wire from equipment cabinets to the nearest AC distribution neutral-ground bond is used to maintain isolation from building conduit. Building conduit is a known source of low frequency noise due 60 Hz currents and high frequency noise during lightning events.
Will additional earth ground references to an equipment cabinet reduce noise interference?
An additional earth ground reference that is not bonded to the building grounding system (an NEC code violation) may actually create more noise and risk equalizing lightning induced currents on the original safety ground. This can elevate equipment cabinet potentials resulting in hardware failure.
Is lead length important in the installation of transient overvoltage protectors?
Lead lengths must be as short and direct as possible to avoid delay in the protector's response time and increased limiting voltage at the application point due to added wire inductance.
