Grounding and Bonding Questions
Questions we encounter most often are listed below. For other grounding questions not addressed or anwered please email us, as we are always glad to be of assistance.
What is the advantage of a Ufer grounding system?
A Ufer ground is a grounding product consisting of metal bars that are encased in concrete and buried a few feet under ground. Approved by NEC as a "Concrete Encased Electrode," A Ufer grounding system is a good solution for locations where rock or other barriers prevent deeply driving a single ground rod. If properly sized, the large mass of concrete can achieve acceptable earth ground impedance while only buried a few feet deep.
What is the difference between a ring ground and a halo ground?
A ring ground is external to the structure while the halo ground is internal. A ring ground consists of a #2 AWG bare wire buried a minimum depth of 30" in the soil encircling a structure. A feature to the ring ground is that is serves as an NEC approved alternative to a single driven ground rod. A halo ground is a product that consists of bare or insulated wire and runs around the ceiling of a structure or equipment room and is, typically, bonded to the corners of a buried ring ground. A halo ground acts as a shield for reducing RFI (radio frequency interference) from electromagnetic fields.
What is an isolated ground?
Building conduit is inherently a source of low frequency noise, operating with a frequency of 50 or 60 Hz. In addition, it can conduct high frequency noise during lightning events. An isolated ground is a separate, insulated safety ground wire that connects an equipment cabinet to the nearest ac distribution neutral-ground bond. It is used to maintain isolation from building conduit.
Will an earth ground bond to an equipment cabinet reduce noise?
An additional earth ground reference that is not bonded to the building grounding system (an NEC code violation) may actually create more noise. It introduces the potential of lightning induced currents equalizing on the original safety ground. This would elevate equipment cabinet potentials, which would be a safety hazard and possibly cause equipment failure.
Is lead length important in the installation of transient overvoltage protectors?
Lead lengths must be as short and direct as possible. A wire’s inductance increases over length, causing a delay in the protector’s response; subsequently the let through voltage is increased.