Standard Dimensions Of Distribution Boxes

There is no single mandatory standard for the size of a distribution box; its size is primarily determined by the number and specifications of the electrical components installed inside. Based on the usage scenario, the following are common size selections.

Core Principle: Modular Circuits
The core of distribution box size calculation is the "module." One module (1M) has a width of 18mm.

A 1P single-pole circuit breaker typically occupies the width of one module (18mm).

A 2P double-pole circuit breaker or one with residual current protection typically occupies the width of two modules (36mm).

The width of the distribution box ≈ (total number of switch modules × 18mm) + reserved space on both sides. For example, the depth of a household distribution box is typically between 100mm and 150mm to allow for embedding in the wall.

1. Residential Distribution Box

The PZ30 series is the most common standard series in residential buildings. Its core logic is based on the number of units; 1 unit = 18mm width, and the box width increases with the number of units.

Standard dimensions for concealed wall mounting (width × height × depth, in mm):

4-6 units for small apartments: approx. 200×300×90 mm

8-10 units for standard two-bedroom apartments: approx. 250×300×90 mm or 300×300×90 mm

12-15 units for three/four-bedroom apartments: approx. 350×400×90 mm or 400×450×100 mm

18-20 units for duplexes/large single-level apartments: approx. 450×500×100 mm or 500×600×100 mm

The depth of a residential concealed distribution box is typically 90mm-100mm; a wall groove depth of ≥120mm must be reserved.

2. Commercial or small power distribution boxes are commonly used in shops, office buildings, etc., and are larger than those for residential use.

Common dimensions: For example, 600×800×200mm (width×height×depth) or 800×1000×220mm.

Other references:
User box: 390×300×100mm
Centralized meter box: 1140×1020×125mm
Dual power/emergency power box: 450×360×150mm

3. Industrial and commercial distribution box dimensions
Distribution boxes used in industrial or commercial projects are typically larger and often custom-made. Reference dimensions for common types:
Small to medium-sized power/lighting boxes: Common sizes include 400×500×150mm, 500×600×180mm, etc.

Large floor-standing distribution cabinets: These cabinets typically have a uniform height. For example, the GGD type fixed switch cabinet commonly measures 800mm wide × 800mm deep × 2200mm high.

Other references: Common electrical cabinet dimensions also include 400×600mm, 600×800mm, and 600×1000mm.

Note: Installation height: The center point of a fixed distribution box should be 1.4 to 1.6 meters from the ground.

Verticality: The verticality deviation of the cabinet installation should not exceed 1.5‰.

Cabinet material: Cold-rolled steel plate (1.2–2.0mm thick) or flame-retardant insulating material should be used. The use of wood is strictly prohibited.