1. Installation Location Requirements (GB 50303)
GB 50303 Location requirements for the equipotential bonding terminal box:
- The MEB is installed at thepower supply incoming point(electrical room or floor distribution room), close to the PE bar.
- The LEB is installed inWithin the local zone(e.g., inside a bathroom wall), at the point closest to that zone's metal piping.
- Do not install inlocations exposed to direct water spray(e.g., directly below a shower head).
- The location must remain accessible for maintenance; do not seal the box inside a non-removable decorative layer.
2. Installation Height (MEB vs LEB)
| Type | Mounting height | Method | Notes |
|---|---|---|---|
| MEB | Bottom edge 0.5–1.5 m above floor | Surface-mounted / flush-mounted | Inside electrical room |
| LEB | Bottom edge 0.3–0.5 m above floor | Primarily flush-mounted | Bathrooms / machine rooms |
| LEB (machine room) | Bottom edge 0.3 m above floor | Flush mount | Below raised access floor |
3. Bonding Conductor Cross-Section (GB 50057)
GB 50057 Requirements:
① MEB to ground electrode:copper ≥ 25 mm² or copper busbar 25×4
② MEB to each pipe:Copper ≥ 6mm²
③ LEB to each pipe/equipment:Copper ≥ 6mm²
④ LEB to MEB:Copper ≥ 16mm²
⑤ Conductor color:Yellow-green striped
4. Connection Methods (3 Types)
| Connection Methods | Application | Conductor Size |
|---|---|---|
| Bolted compression connection | Copper busbar / copper terminals | ≥ 6mm² |
| Exothermic welding | Copper-to-copper / copper-to-steel | ≥ 16mm² |
| Cable lug compression | Conductor to copper busbar | ≥ 6mm² |
5. Acceptance Checklist (6 mandatory checks)
- Location: MEB at the incoming supply, LEB within the local area
- Height: MEB 0.5–1.5 m, LEB 0.3–0.5 m
- Connect: All metal pipes, equipment and rebar are bonded
- Cross-section: Conductor cross-sections meet GB 50057 requirements
- Color: Conductors are green/yellow two-color
- Continuity: LEB is connected to MEB; continuity test passed
FAQ FAQ
At what height is the equipotential bonding terminal box installed?
MEB: bottom edge 0.5–1.5 m above floor; LEB: bottom edge 0.3–0.5 m above floor. Do not install where it is directly exposed to water spray.
What color are equipotential bonding conductors?
Yellow-green striped(standard PE color), matching the equipment grounding conductor.
What is the cross-section of the LEB-to-MEB bonding conductor?
≥ 16mm² copper(BVR-16mm²); do not substitute a smaller cross-section.
Can the equipotential bonding terminal box be surface-mounted?
The MEB may be surface-mounted in the electrical room; the LEB is generally flush-mounted inside bathroom walls, since surface mounting affects appearance.
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