Main earthing terminal
Hoofdaardrail (HAR)
Also known as: meb, main-earth-bar, aardrail, busbar, verzamelrail, rail
Central connection point where PE, earth electrode, and main equipotential bonding converge. Forms the physical reference point for the installation earth.
Practical example
Main earthing rail (MER). In the distribution board, the earth electrode, the PE of the consumer unit, and the equipotential bonding of gas and water pipes are all connected to the same main earthing rail.
Common mistake
Main earthing rail (MER). Common mistake: Connecting loose earth bonds directly to any metal pipe instead of via the MER — this makes earth resistance unpredictable and not measurable at a single point.
See also
Related terms
- Equipotential bonding
- PE (Protective Earth)
- Main earthing electrode
- Main low-voltage distribution board (MDB)
- Earth Fault Factor (IT System)
- Earthing Grid (Ground Mat) — Substation / HV Yard
- Fire-Protection RCD (300 mA)
- Automatic Self-Test Emergency Lighting System (Addressable)
- Exothermic Welding (Earthing Connection)
In-depth guides
- → Earthing and earthing systems (TN, TT, IT)
- → §544 Main bonding & earthing of greenhouse frames — §544
- → §531 Residual Current Circuit Breakers (RCD)
- → Netcode Elektriciteit Harmonics & THD limits for large consumers
- → §542.4 (IEC 60364-5-54) The main earthing terminal (§542.4) — why every connection must be individually disconnectable for measurement
- → §411.3.1.2 Main equipotential bonding — which extraneous-conductive-parts must be connected (§411.3.1.2)
- → §536.4.2 Network operator's main fuse versus the first installation breaker — selectivity or back-up protection
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