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Electrical Connections 7
3.2.1 System Grounding and Bonding
The performance and safety of any TVSS system is dependent on proper grounding and bonding.
Grounding is required primarily for safety. Correct implementation also enhances equipment per-
formance. Incorrect grounding can reduce or impede the TVSS's operation.
All electrical circuits to the TVSS must include an equipment grounding conductor as required by
the NEC and local codes.
An insulated grounding conductor is required in addition to any metallic raceway that may be
used as a grounding conductor. For parallel-connected TVSSs, the grounding conductor should be
the same wire size as the associated power conductors. Grounding conductors must be routed with
the associated power conductors in the same raceway (conduit).
When metallic raceways are used, adequate electrical continuity must be maintained at all race-
way connections, particularly raceway terminations to the electrical enclosures.
The use of isolating bushings or other means to interrupt a metallic conduit run is a potential
safety hazard and is not recommended.
Grounding Electrode—Transient voltage surge suppressors do not discharge all surges to
ground (earth). Transient voltage surge suppressors divert the surge current back to its source to
complete the electrical circuit.
In the case of lightning whose potential is developed with respect to the earth, the TVSS diverts
the surge current to the grounding electrode (earth connection). However, for most transient
surges which are developed by switching loads, the TVSS diverts the surge current back to its
source without involving the grounding electrode.
For proper TVSS performance, the service entrance grounding electrode system must comply with
the NEC by having all available electrodes (building steel, metal water pipe, driven rods, concrete
encased electrodes, etc.) properly bonded together and connected to the power system grounding.
!
CAUTION
The use of a separate grounding electrode to ground the TVSS
defeats the effectiveness of the TVSS, is a potential safety hazard,
and may cause equipment damage. The arrestor grounding
conductor must be connected per NEC 280-21.
!
CAUTION
For proper and safe operation, the neutral, (if provided), must be
reliably connected to the neutral of the source. Failure to provide
a reliable neutral connection may result in module failure!