Ss 551 Code Of Practice For Earthing May 2026

To eliminate dangerous voltage differences between metallic parts, SS 551 requires bonding.

The TN system is the default for most installations in Singapore. It is subdivided into:

One of the deep features of SS 551 is its obsession with the specific. It does not offer a "one size fits all" solution. It demands rigorous calculation.

Clause by clause, the code navigates engineers through the treacherous waters of local geology. In land-scarce Singapore, where high-rise foundations go deep into reclaimed land or varying rock strata, the resistivity of the soil is a nightmare variable. ss 551 code of practice for earthing

SS 551 mandates specific testing methods—like the Wenner or Schlumberger methods—to measure how well the earth conducts electricity. It forces engineers to calculate the "step potential" (the voltage difference between a person’s feet) and "touch potential" (the difference between a hand and a foot). These aren't just numbers on a page; they are the mathematical difference between a minor tingle and a fatal cardiac arrest.

The code also details the materials of the trade. We are no longer in the era of a simple copper rod. SS 551 outlines specifications for copper-bonded steel, solid stainless steel, and intricate earthing mats. It addresses corrosion—a silent killer of infrastructure—ensuring that the earth connection installed today will still function twenty years from now when the concrete has set and the building is fully occupied.

SS 551 applies to earthing systems in:

Crucially, the code does not apply to earthing for lightning protection systems (covered under SS 555) or special installations like explosive atmospheres (SS 60079 series), though it references them where interfaces exist.

An earthing system is only as good as its documentation. SS 551 mandates specific tests after installation and at regular intervals:

Initial Tests:

Periodic Tests (per EMA regulations):

According to SS 551, a properly designed earthing system must achieve three main goals: