How to choose a distribution box: ways count, IP rating by location, flush vs surface, and metal vs plastic enclosures.
A distribution box, also called a distribution board, consumer unit or panelboard, is the enclosure that holds your circuit breakers, RCDs and busbars and splits the incoming mains into protected final circuits. Specify the wrong one and you either run out of ways before the installation is finished or you mount an indoor-rated box where it gets rained on. This guide covers the parameters a buyer or panel builder actually specifies.
"Ways" is the number of protective-device positions (MCBs, RCDs, RCBOs) the board can hold. The common mistake is counting only the circuits you have today. A small office that needs 8 ways now typically needs 12 to 14 once you add spares, a dedicated RCD section and future expansion. As a rule, take the current circuit count and add 25 to 30% headroom: a board at 100% capacity cannot accept a later upgrade without being replaced.
| Installation | Ways needed now | Board to buy |
|---|---|---|
| Studio / 1-bed flat | 6 to 8 | 12-way |
| 3-bed house | 10 to 12 | 16 to 18-way |
| Small commercial unit | 16 to 20 | 24 to 36-way |
| Machine control panel | 8 to 16 | +30% spare |
The IP (Ingress Protection) code decides what the enclosure keeps out. An indoor board in a dry electrical room is fine at IP30 or IP40. The moment the board sits in a car park, plant room, workshop or any outdoor wall, you need IP65 (dust-tight, low-pressure water jet) at minimum, and IP66 where it is hosed down or fully exposed. Fitting an IP40 box outdoors is the most common cause of corrosion and nuisance RCD trips we see on site.
| IP code | Protected against | Use it for |
|---|---|---|
| IP30 / IP40 | Solids greater than 2.5 mm, light touch | Indoor dry rooms |
| IP54 | Dust + splashing water | Covered plant areas |
| IP65 | Dust-tight + water jets | Outdoor / wash-down |
| IP66 | Strong water jets | Hosed / exposed sites |
A flush (recessed) box sits inside a cavity or partition wall and gives a clean, space-saving finish in homes and offices. A surface (wall-mounted) box stands proud of the wall and is the only option for concrete, external walls or retrofits where chasing is impractical, and it is easier to service. Let the wall construction decide first; aesthetics come second.
Plastic (insulated) enclosures are lighter, cheaper, never rust and are safe to touch, which makes them the default for residential consumer units. Metal enclosures give higher mechanical strength and better electromagnetic shielding for industrial and commercial panels, but they must be properly earthed and can corrode in damp locations unless powder-coated or stainless. For most low-voltage panel-build jobs the choice is driven by environment and impact risk, not price.
Decide how the incoming supply is controlled and how earth-fault protection is arranged:
Also check the DIN-rail pitch, the neutral and earth terminal bars (can they take your cable count?) and whether there is routing space so the lid closes without crushing conductors.
ELEHPD supplies MG, ZY, ME, FE, LGD and PCU distribution boxes in flush and surface versions with IP30 to IP65 ratings and single- and three-phase incomers, ready to be assembled with MCB, RCD and RCBO configurations to IEC practice.
Send the ratings, dimensions and quantities you are working to and we will confirm the closest match from the ELEHPD catalogue, the compliance documents available for it and the lead time. OEM branding, private model numbering and buyer-specific cartons are available on qualified volumes.