1. How many types of junction box are there? One table sorts it out
Junction boxes are classified byIP rating, material and mounting method— three dimensions:
| Category | Sub-type | Typical applications |
|---|---|---|
| By protection | IP54 waterproof / IP65 outdoor / IP66 high-pressure water jet / IP68 submersible | Outdoor, damp, submersible |
| By material | ABS plastic / powder-coated cold-rolled steel / 304 stainless steel / 316 stainless steel | Indoor, outdoor, chemical |
| By mounting | Surface-mount (wall-mounted) / flush-mount (recessed in wall) / floor-standing / suspended | Fit-out / industrial / outdoor |
| By function | Standard wiring / explosion-proof / equipotential bonding / fire alarm terminal | General purpose / hazardous area / bathroom |
Indoor dry area → ABS plastic surface-mount; general outdoor → sheet steel IP65; coastal / chemical → 304/316 stainless steel; hazardous area → explosion-proof; bathroom / washroom → equipotential bonding terminal box.
2. Waterproof junction boxes: standard equipment for outdoor and damp environments How to choose an IP rating
The core of a waterproof junction box is Second digit of IP(water protection rating):
| IP rating | Meaning | Typical applications | Zhejiang Golden Unicorn default material |
|---|---|---|---|
| IP54 | Water splashed from any direction has no harmful effect | Under a canopy / tunnel | ABS / powder-coated sheet steel |
| IP65 | Low-pressure water jets from any direction have no harmful effect | Fully outdoor / street lighting | ABS / sheet steel / 304 |
| IP66 | Powerful water jets | Seaside / heavy rain zones | 304 / 316 |
| IP67 | Temporary immersion (1 m / 30 min) | Buried / short-term submersion | 316 / engineering plastic |
| IP68 | Continuous immersion | Underwater lighting / fountains | Engineering plastic + sealing gasket |
Sealing design of Zhejiang Golden Unicorn waterproof junction boxes:Door with silicone gasket + stainless steel hinges + stainless steel latches + cable glands in PG11 / PG13.5 / PG16 / PG21 / M20 / M25 sizes.
3. Explosion-proof junction boxes: for hazardous areas only Ex d vs. Ex e: what is the difference
Explosion-proof junction boxes are used inexplosive gas atmospheres(chemical / oil & gas / pharmaceutical / paint spray booths). Chinese national standards classify them as:
| Explosion-proof type | Code | Principle | Application |
|---|---|---|---|
| Flameproof | Ex d | Contains internal explosion, prevents propagation to the surrounding atmosphere | Gas atmosphere Zone 1 / Zone 2 |
| Increased safety | Ex e | Higher safety factor | Zone 1 / Zone 2 low-hazard areas |
| Pressurized | Ex p | Maintains positive internal pressure | Large control cabinets |
| Intrinsically safe | Ex i | Limits circuit energy | Instrumentation / signals |
Explosion-proof products are manufactured in joint supply with an Ex-qualified specialist factory.Zhejiang Golden Unicorn can take on explosion-proof junction box orders,Ex certificate verification available,specific explosion-proof ratings (Ex d IIB T4 / Ex d IIC T6, etc.) are subject to the partner's certificate scope.
4. Stainless Steel Junction Boxes: Chemical, Food & Coastal How to choose the material
Stainless steel junction boxes come in two main grades, 304 and 316:
| Material | Nickel content | Corrosion resistance | Application | Zhejiang Golden Unicorn price difference |
|---|---|---|---|---|
| 304 stainless steel | 8–10% | General outdoor / food-grade | Most outdoor / food plant floors | Base price |
| 316 stainless steel | 10–14% + 2–3% molybdenum | Severe corrosion / seawater | Coastal / chemical / offshore platforms | 30–50% more expensive |
Zhejiang Golden Unicorn stainless steel junction boxes ship as standard with304 material,sheet thickness 1.2–1.5 mm, laser cutting ±0.1 mm, 9-bend forming, door gap ≤1 mm, compliant with GB 4208 enclosure ingress protection requirements.
5. Surface-Mount / Flush-Mount Junction Boxes: Selection by Fit-Out Stage Mainly ABS plastic
The most widely used type at the fit-out stage is ABS plastic junction boxInexpensive, lightweight, flame-retardant. Common sizes:
| Size | Dimensions (mm) | Cable entry holes | Application |
|---|---|---|---|
| 86-type | 86 × 86 × 35 | 4–6 | Standard 5-hole socket / single-gang switch |
| 118-type | 118 × 74 × 50 | 6–8 | Multi-function socket combination |
| 120-type | 120 × 74 × 50 | 8–10 | Large combination |
| Round | Φ60 / Φ80 | 3–4 | Ceiling light / downlight wiring |
Surface mount vs. flush mount:Surface mountNot recessed into the wall; comes with its own back box and sits exposed on the wall surface;Flush mountRequires recessed wall installation with a dedicated flush-mount back box. Flush mount looks cleaner but has wall thickness requirements (depth ≥ 50 mm).
6. Equipotential bonding terminal box: mandatory for bathrooms / washrooms The last line of defense against electric shock
The equipotential bonding terminal box is a bathroom / washroom electric shock protection requirement (GB 50096-2011 Residential Design Code, Clause 8.7.7). Function: connect all conductive metal parts (shower heads / water pipes / faucets / bathtubs) by conductor to the equipotential bonding terminal block, which is bonded to the building's main ground.
| Mounting location | Terminals | Conductor size | Zhejiang Golden Unicorn equivalent |
|---|---|---|---|
| Bathroom | 6-position | BV 4 mm² yellow-green two-color | et-6a-wc |
| Washroom | 6–8 position | BV 4 mm² yellow-green two-color | et-8a-bath |
| Swimming pool | 8–12 position | BV 6 mm² yellow-green two-color | et-12a-pool |
Equipotential terminal boxCore componentsare copper terminal blocks (typically T2 copper, nickel-plated), available in 5-position / 8-position / 12-position configurations, with surface-mount or flush-mount options.
7. Shop Floor Photos: 4 Images of Junction Box Assembly Workmanship (shop floor photos)
The following are from theTonglu Fengchuan Industrial Zone assembly lineShot on site. If you need cut-out product images for a catalog or brochure, message us on WhatsApp: +86 186 5712 0011.
FAQ FAQ
Outdoor junction box: ABS or stainless steel?
For general outdoor use, choose ABS (cheaper), for coastal / chemical environments choose 304 / 316 stainless steel. ABS junction boxes become brittle under intense UV and large temperature swings, requiring replacement in 3–5 years; stainless steel lasts 10+ years. Stainless steel unit price is typically several times that of ABS in the same size — weighing cost against service life by environment is the better value.
Can flush-mount and surface-mount junction boxes be interchanged?
No.A flush-mount box is designed to be embedded in the wall, with no space reserved for a back box; a surface-mount box is designed to mount on the wall surface, with its own mounting holes. Mixing them will result in a box that won't fit or sits crooked.Decide which type before renovation — it can't be changed midway.
Is an equipotential terminal box mandatory?
Mandatory for bathrooms / shower rooms(GB 50096-2011 Clause 8.7.7); not mandatory elsewhere but recommended. If omitted, renovation inspection will be rejected, and insurance claims may also be denied (electrical shock incidents are considered human negligence).
How do you read the explosion-proof rating on an explosion-proof junction box?
Explosion-proof marking format:Ex d IIB T4.Ex = explosion-proof;d = flameproof;IIB = gas group (IIB includes ethylene, dimethyl ether, etc.; IIC includes hydrogen);T4 = maximum surface temperature 135°C. Common selections: IIB T4 for chemical, IIC T6 for oil & gas.
What is used for junction box cable entry holes?
Cable glands (cable connectors / waterproof glands), sized by cable outer diameter: PG11 (Φ5–10mm), PG13.5 (Φ6–12mm), PG16 (Φ10–14mm), PG21 (Φ13–18mm), M20 (Φ7–13mm), M25 (Φ12–19mm). Golden Unicorn supplies nickel-plated brass glands by default, IP65 and above.
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