What is the minimum length that conductors should be when laid in trenches within shallow sandy or gravelly soil?

The minimum length that conductors should be when laid in trenches within shallow sandy or gravelly soil is 12 feet. This specification is in accordance with safety standards that aim to ensure adequate grounding and bonding for lightning protection systems. Conductors need to be long enough to provide effective grounding by reaching a depth and distance that allows for proper dissipation of lightning energy into the ground.

The dimensions are critical to avoid increasing resistance, which can occur if the conductors are too short or improperly placed. In sandy or gravelly soils, which may have lower moisture content, a longer conductor helps achieve a better electrical connection to the ground. This is important to ensure that any lightning strike is safely discharged, reducing risks and protecting structures from damage.

Therefore, maintaining a minimum length of 12 feet helps to ensure the effectiveness of the lightning protection system within these types of soil conditions.