1. What Determines the Size? (3 Factors)
Enclosure size = circuit count × breaker width + heat dissipation clearance + wiring space. More circuits and larger breakers mean a wider enclosure.
2. Circuit Count → Enclosure Size Table (PZ30 Terminal Box)
| Circuit Count | DIN Rail Modules | Enclosure Size (mm) | Installation |
|---|---|---|---|
| 12 circuits | 12 | 300×240×120 | Flush mount |
| 24 circuits | 24 | 400×300×120 | Flush mount |
| 36 circuits | 36 | 500×400×150 | Flush mount |
| 48 circuits | 48 | 600×400×150 | Surface mount |
3. Power Distribution Box Size Table (XL-21)
| Current | Cabinet width | Cabinet depth | Cabinet Height |
|---|---|---|---|
| ≤ 250A | 600 | 300 | 1600 |
| 250–400A | 600 | 370 | 1800 |
| 400–630A | 800 | 370 | 2000 |
| 630–1250A | 800 | 600 | 2200 |
4. Mounting Height Code (GB 50054)
Distribution box bottom edge above floor:Surface-mounted 1.5–1.8mFor flush mounting, 1.4–1.6 m; keep ≥ 0.8 m of clear working space in front of the operating face. For floor mounting, use a base ≥ 100 mm.
5. Heat dissipation clearance (leave top and bottom)
Switches inside the enclosure must be arranged withleave ≥ 50 mm at top and bottom heat dissipation clearance; higher-current breakers need more. Tightly packed arrangements cause excessive temperature rise — GB/T 7251.1 requires busbar temperature rise ≤ 70K.
FAQ FAQ
How do you size a distribution box?
Number of circuits × breaker width + heat dissipation clearance + wiring space. If you can't work it out, send us your drawing — Zhejiang Golden Unicorn will size it free of charge.
What mounting height is suitable?
Surface mounting: bottom edge 1.5–1.8 m. Flush mounting: 1.4–1.6 m. Leave ≥ 0.8 m clear in front of the operating face.
What happens if the enclosure is too small?
Insufficient heat dissipation, excessive temperature rise, shortened breaker life, and in severe cases burnout.
Can you build custom non-standard sizes?
Yes. Zhejiang Golden Unicorn builds to drawing, MOQ 1 unit, 15–25 day lead time.
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