4. Earthing & Bonding for Protection · Page 4 of 6
The SPD-to-Earth Path
The most overlooked detail in failed surge protection jobs.
Keep it short and straight
Every extra meter of PE conductor adds inductance. Under a fast surge, that inductance creates voltage that appears at the protected bus—even if the SPD clamps perfectly at its terminals.
Avoid coils and loops
Do not spiral spare cable. Cut to length. Route phase/neutral/PE leads of the SPD close together to minimize loop area.
Target practice
Many guides aim for total SPD connection length well under 0.5 m per lead where physically possible.