1. The 3 Main Functions of an Equipotential Bonding Terminal Box GB 50096-2011, Clause 8.7.7
The 3 main functions of an equipotential bonding terminal box:
- Shock protection: eliminates potential differences between metal parts, so even under leakage no contact voltage hazardous to people is produced (< 50V)
- Electromagnetic interference suppression: once metal parts are at equal potential, the influence of external electromagnetic fields on sensitive equipment is reduced
- Supplementary grounding: the equipotential bar can serve as an extension of local grounding, lowering grounding resistance
GB 50096-2011 "Code for Design of Residential Buildings," Clause 8.7.7:Residential bathrooms should have equipotential bonding; since GB 50096-2011 took effect, new residential buildingsmust install it. GB 50054-2011, Clause 5.2.9: medical facilities, swimming pools and bathrooms must have equipotential bonding.
2. Equipotential Bonding vs. Grounding: What's the Real Difference? Not the same thing — and often confused
| Item | Equipotential bonding | Protective grounding (PE) |
|---|---|---|
| Purpose | Eliminate potential differences to prevent electric shock | Provide a leakage current path to trip protection |
| Connects to | Metal parts interconnected with each other | Metal enclosure connected to the PE bar / ground electrode |
| Mandatory locations | Bathrooms / shower rooms / swimming pools / hospitals | Metal enclosures of all electrical equipment |
| Grounding resistance | May share the main ground, ≤ 4Ω | ≤ 4Ω (residential) / ≤ 10Ω (separate grounding) |
| Standards | GB 50054-2011 Clause 5.2.9 | GB 50054-2011 Clause 5.2.7 |
Both must be installed at the same time. Equipotential bonding eliminates potential differences; grounding provides a leakage path. Neither can be omitted.
3. Four Installation Locations: Bathroom / Shower Room / Swimming Pool / Hospital Different locations, different terminal counts
| Location | Terminals | What it bonds | Matching Zhejiang Golden Unicorn model |
|---|---|---|---|
| Bathroom | 6-position | Shower head + faucet + water pipe + bathtub + heating + spare | et-6a-wc |
| Washroom | 8-way | Bathroom 6-way + sauna + steam room | et-8a-bath |
| Swimming pool | 12-way | Pool wall + underwater lights + circulation pump + heater + 6 perimeter points | et-12a-pool |
| Hospital operating room | 8-way | Operating table + surgical light + anesthesia machine + ECG monitor + 4 perimeter points | et-8a-icu |
equipotential bonding terminal boxTypically mounted inside the bathroom wall (flush) or on the wall surface (surface-mount), at a height of 0.3–0.5m. Surface-mount boxes require a lockable cover to prevent children from accidental contact. Flush-mount boxes require a pre-cut wall opening with a box depth ≥ 60mm.
4. 5-Step Wiring Method: From Terminal to Metal Part Standard on-site installation steps
- Step 1:Mount the terminal box in the wall or on the wall (surface or flush mount)
- Step 2:Run 1 conductor from the terminal box to the building main grounding bar BV 6 mm² green/yellow two-color wire
- Step 3:Run 1 conductor from the terminal box to each shower head / faucet / water pipe BV 4 mm² green/yellow two-color wire
- Step 4:Secure each metal part with a dedicated grounding clamp (copper, toothed bite) to ensure good conductivity
- Step 5:Measure the resistance between the terminal box and the main ground with a ground resistance meter; it should be ≤ 0.5Ω(dedicated equipotential requirement, stricter than protective grounding)
Zhejiang Golden Unicorn equipotential bonding terminal box standard configuration: ① T2 copper terminal block, nickel-plated ② 5 / 8 / 12 positions available ③ green/yellow two-color wire 4 mm² / 6 mm², custom lengths available ④ surface mount / flush mount / IP54 — three versions.
V. Factory photos: 4 shots of terminal box assembly workmanship (shop floor photos)
FAQ FAQ
Is an equipotential bonding terminal box mandatory? What happens if you skip it?
Mandatory in residential bathrooms / shower rooms(GB 50096-2011 Clause 8.7.7); if omitted, acceptance inspection fails.The most serious consequence of omitting it: when the shower head leaks current, a 220V potential difference forms between the shower head and the water pipe; touching any metal part delivers a shock, and in severe cases it can be fatal.
What wire size is used for an equipotential bonding terminal box?
Terminal box to building main ground:BV 6 mm² yellow-green two-color; terminal box to each metal part:BV 4 mm² yellow-green two-color. Copper conductors are required — aluminum wire is not allowed (connections oxidize easily and make poor contact).
My old house has no equipotential bonding terminal box — can one be added later?
Yes, but it requires partial renovation. Steps: ① Locate the building main ground (the PE bar in the distribution box or the main grounding electrode) ② Install an equipotential bonding terminal box at a suitable location in the bathroom ③ Run BV 6 mm² wire from the terminal box to the main ground ④ Run BV 4 mm² wire from each metal part back to the terminal box.Have a licensed electrician do the work; do not run the wiring yourself.
Does an equipotential bonding terminal box need a grounding resistance test?
It must be tested. Measure the resistance between the terminal box and the main ground;it should be ≤ 0.5Ω(stricter than the 4Ω for protective grounding). You can use a ground resistance meter or a multimeter on the mΩ range. This is a mandatory check at acceptance inspection.
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