1. What exactly is the difference between a distribution box and a distribution cabinet? One rule of thumb tells them apart
Rule of thumb:"Small and shallow is a box; large and deep is a cabinet.". By convention:
| Item | distribution box | distribution cabinet |
|---|---|---|
| Typical Capacity | ≤ 250 A | ≥ 250 A |
| Typical height | ≤ 1000 mm | ≥ 1600 mm |
| Typical depth | ≤ 300 mm | ≥ 400 mm |
| Main standard | GB/T 7251.3 | GB/T 7251.1 |
| Typical use | Indoor / outdoor terminal | Shop-floor / floor-level main distribution |
In real projects, though, the two terms get used interchangeably — people say "distribution box" out of habit even for a 2000 A unit. This article goes bypractical selection, not by wording.
2. Lighting distribution box: offices / retail / residential Indoor, IP30–IP40
A lighting distribution box isthe most common type of terminal box, wall-mounted surface or flush-mounted indoors. Common sizes:
| Rating | Dimensions (mm) | Circuits | Main breaker | Application |
|---|---|---|---|---|
| 6 circuits | 300 × 200 × 110 | 6 × 1P | 40 A 2P | Small apartments / retail shops |
| 12 circuits | 400 × 300 × 110 | 12 × 1P | 63 A 2P | Standard 3-bedroom home |
| 18 circuits | 500 × 400 × 110 | 18 × 1P | 100 A 2P | Small offices |
| 24 circuits | 600 × 500 × 110 | 24 × 1P | 100 A 2P | Office building floors |
Zhejiang Golden Unicorn lighting boxes come standard with Schneider C65 series miniature circuit breakers, optional surge protection, and a 5-position N bar + 5-position PE bar, compliant with GB 50054-2011 Clause 5.2.7.
3. Power Distribution Boxes: Dedicated to Workshop Equipment 3-phase power + ground fault protection
The key requirement for a power distribution box is 3-phase 380 V + ground fault protection, commonly found in:
- Machine tools / machining centers: each unit on a dedicated circuit at 7.5–22 kW, with breaker + contactor + thermal overload relay
- Pumps / fans: duty/standby rotation, with breaker + dual contactors and mechanical interlock
- Compressors / injection molding machines: high inrush current, so breakers are derated to 80% of rated capacity
The main incoming line of a power distribution boxmust have ground fault protection(30 mA, tripping at ≤0.1 s). This is mandatory under GB 50054 Clause 5.2.5 and cannot be omitted. Select a 4-pole 30 mA ground fault protection device, installed after the main breaker, with a separate branch breaker on each of the 4 outgoing circuits.
4. Outdoor Distribution Boxes: IP65 / Stainless Steel / Waterproof Environment matters more than capacity
The core specification for an outdoor distribution box is IP rating. Zhejiang Golden Unicorn's common configurations:
| Environment | Recommended rating | Recommended material | Construction details |
|---|---|---|---|
| General outdoor (under a canopy) | IP54 | Powder-coated cold-rolled steel | Gasketed door + ventilation hood |
| Fully outdoor (no cover) | IP65 | 304 stainless steel | Gasketed door + drain holes + rain hood |
| Coastal / chemical | IP66 | 316 stainless steel | Fully sealed + anti-corrosion coating |
| Coastal + high wind | IP66 + wind-resistant lock | 316 stainless steel | Three-point latch + reinforced hinges |
What the IP digits mean:First digit = dust protection, second digit = water protection. IP65 = dust-tight + protected against low-pressure water jets from any direction; IP66 = dust-tight + protected against powerful water jets.
5. Indoor terminal boxes: PZ30 / JP distribution boxes Modular · the standard fit-out choice
PZ30 and JP are the most common terminal boxes at the fit-out stage, both using modular DIN rail + transparent door construction. Differences:
| Item | PZ30 | JP box (distribution box) |
|---|---|---|
| Max capacity | ≤ 100 A | ≤ 250 A |
| Number of circuits | 6–30 circuits | 6–24 circuits |
| Typical use | Indoor terminal / secondary distribution | Indoor main incoming splitter box |
| Price | Low | Medium |
The PZ30 is smaller and thinner, suited to indoor terminals; theJP box is larger and thicker, suited to indoor main incoming splitter boxes. Both are available with transparent doors for easy visual checking of branch circuit status during routine maintenance.
6. Shop-floor photos: 5 close-ups of assembly details (workshop photos)
All of the following arephotographed on the assembly line at the Fengchuan Industrial Area workshop in TongluShot on site. GU ELECTRIC does not publish AI-rendered cut-out product images — we use real production-line photos only. If you need cut-out images for a catalog or brochure, message us on WhatsApp: +86 186 5712 0011.
FAQ FAQ
Is there a big price gap between IP54 and IP65 distribution boxes?
Yes, a significant one 15–25%. IP54 only needs powder-coated cold-rolled steel with a gasket; IP65 also requires 304 stainless steel or thicker powder coating, plus a rain hood and drain holes. For coastal or chemical environments, go straight to 316 stainless steel — add another 30%.
Can a distribution box be fed from the bottom?
Technically yes, butnot recommended. Bottom entry lets condensation run down the busbar and pool at the terminals. Code requirestop entry / top exit or bottom entry / bottom exit, with feed and exit directions consistent; if a bottom feed is unavoidable, always install a backflow-prevention fitting.
Does a distribution box need 3C certification?
Assembled products (distribution boxes / distribution cabinets) use CQC voluntary certification, not mandatory; but some project tenders require a 3C certificate. Low-voltage components (breakers / contactors) require 3C. Zhejiang Golden Unicorn holds ISO 9001:2015 / CE (LVD+EMC) / IP65 test reports in original, and 3C can be applied for per order.
How much space should be reserved for a flush-mounted distribution box?
Enclosure dimensions + 50mm clearance on all sides for heat dissipation + 600mm operating space in front. Example: for a 400×300×110 flush-mounted box, the rough opening is about 410×310×120 (depth). If a ground fault module is added, add 20mm depth.
Can the N bar and PE bar in a distribution box be shared?
They cannot be shared.GB 50054-2011 Clause 5.2.7 mandates that N and PE be kept separate in TN-S systems. Sharing them causes: ① nuisance tripping of ground fault protection ② loss of the TN-S system's purpose ③ abnormal operation of some precision equipment. A common mistake: using a single busbar as both N and PE in small indoor boxes — this will be rejected at distribution acceptance inspection.
Related pages:Technical notes · Products · Industries · Resource center · FAQ · Get a quote