1. Introduction
Hazardous areas-locations with explosive atmospheres due to gases, vapors, or dust-require meticulous earthing and bonding practices to ensure electrical safety. This article outlines the requirements for hazardous area earthing per international standards and the Philippine Electrical Code (PEC) 2017 , including a clause-by-clause summary and a compliance checklist.
2. Objectives of Earthing in Hazardous Areas
- Prevent sparking due to potential differences
- Safely discharge static electricity
- Provide a fault current return path
- Ensure lightning protection
3. International Standards Overview
| Standard | Description |
|---|---|
| IEC 60079-14 | Design & installation of Ex systems - requires bonding of conductive parts |
| IEC 62305 | Lightning protection system design |
| NEC (NFPA 70) | Grounding and hazardous location classifications (Articles 250, 500-516) |
| ATEX Directive 2014/34/EU | EU standard for equipment in explosive atmospheres |
| Clause | Title / Reference | Key Requirement |
|---|---|---|
| Rule 8.0.1.1 (Art. 500) | Classification of Hazardous Areas | Areas must follow NEC-type classification; electrical systems to be grounded accordingly |
| Art. 2.50.4.3 (A) | Equipment Grounding Conductor (EGC) | Exposed metallic parts of equipment must be bonded to the grounding system |
| Art. 2.50.4.5 (A) | Continuity of EGC | EGC shall be continuous and securely connected |
| Art. 2.50.122 | Minimum Size of EGC | Ground conductor sizing based on overcurrent device rating |
| Art. 3.0.3.10 | Bonding & Grounding of Equipment | Non-current carrying conductive parts (piping, vessels) must be bonded for static discharge |
| Art. 504.50 | Grounding of Intrinsically Safe Systems | Intrinsically safe systems must be bonded to earth with low resistance path (< 1 Ohm) |
| Art. 4.20.2.4 | Hazardous Locations Earthing | All conductive parts of the electrical system in hazardous locations must be earthed and inspected |
| Requirement | Specification |
|---|---|
| Ground resistance | ≤ 1 Ohm (typical for Ex environments) |
| Bonding conductor size | ≥ 6 mm² copper or per PEC Table 2.50.122 |
| Static bonding resistance | ≤ 1 Ohm to earth |
| Conductor material | Copper, corrosion-resistant |
| Lightning protection | Use IEC 62305 or IEEE 998 standard design |
| # | Requirement | PEC Reference | Compliant (✓/✗/N/A) | Remarks |
|---|---|---|---|---|
| 1 | Hazardous area classified (Class I/II/III, Div or Zone) | Rule 8.0.1.1 | ||
| 2 | All non-current carrying metal parts bonded | 2.50.4.3(A) | ||
| 3 | Continuity of equipment grounding verified | 2.50.4.5(A) | ||
| 4 | Grounding conductor sized appropriately | Table 2.50.122 | ||
| 5 | Process vessels and piping bonded for static control | 3.0.3.10 | ||
| 6 | Grounding of intrinsically safe circuits provided | 504.50(A) | ||
| 7 | Resistance to earth measured ≤ 1 Ohm | 504.50(A)(2) | ||
| 8 | All bonding connections mechanically secure | 2.50.4.3(A) | ||
| 9 | Lightning protection system designed & earthed | Refer to IEC 62305 | ||
| 10 | Periodic inspection and testing documented | 4.20.2.4 |
The Philippine Electrical Code (PEC 2017) integrates grounding and bonding principles aligned with international standards like IEC 60079 and NEC. For hazardous areas, strict compliance with these codes ensures personnel safety, equipment protection, and regulatory acceptance. The clause-by-clause summary and checklist provided here support engineers in ensuring full code adherence in Ex-rated installations.
8. Abbreviations
| Acronym | Definition |
|---|---|
| PEC | Philippine Electrical Code |
| NEC | National Electrical Code (NFPA 70) |
| IEC | International Electrotechnical Commission |
| Ex | Explosion-proof |
| EGC | Equipment Grounding Conductor |
| ATEX | Atmosphères Explosibles |
| TN-S / TT | Earthing system types |