Industrial & Commercial Electrical Back Boxes: How to Specify
In factories, warehouses, data halls, and plant rooms, the “small” decision of which electrical back box to use can make a big difference to safety, uptime, and the ease of future upgrades. This guide explains how to choose and specify back boxes for industrial and commercial settings in Singapore—aligned to SS 638, BS 4662, and IEC IP/IK protection standards

What exactly is a back box (and why it matters in industry)?

A back box (pattress/mounting box) houses terminations behind a switch, socket, or control device, provides mechanical protection, and gives you a robust mounting interface. In Singapore (BS-type accessories), dimensions and fixing centres follow BS 4662 for flush boxes—so your accessories line up and fit correctly across brands.

Box types for industrial & commercial use

1) Flush-mount galvanized steel boxes

Best for: Masonry or solid walls; control rooms; general commercial fit-outs.
Why: Rigid, broadly compatible with BS accessories; easy earthing via box terminal.

2) Flush-mount PVC boxes

Best for: Non-metallic systems, corrosion-prone locations, or where isolation from earth is desired.
Spec notes: Match conduit entries and use grommets/bushes per good practice and SS 638.

3) Surface mounted/industrial enclosures

Best for: Retrofits on concrete walls, production areas with exposed containment, or when chasing is not feasible.
Spec notes: Select by environment—IP & IK ratings matter more than aesthetics in plant areas.

Depth, dimensions & fit (what actually works on site)

• Depth choice:

  • 25 mm (shallow): tight chases; light-duty switching.

  • 35 mm (standard): the reliable default for sockets and most devices.

  • 47 mm (deep): dimmers, smart modules, multiple feeds, or stiffer industrial cables.
    Manufacturer catalogues show these as standard options with the BS 4662 pattern and 60.3/120.6 mm fixing centres. Farnell

• Physical sizes:
  Example 1-gang flush steel box around 72 × 72 mm body footprint (cut-out area), with the faceplate ~86–88 mm square depending on the accessory family.
  Do check with the user on the total amount of gangs or combinations of plugs and sockets they require

• Knockouts & entries:
  Look for 20 mm (and in many cases 25 mm) knockouts to align with your conduit/trunking. Different back boxes have differnt number of entrires and sizes of entries. It is important to know what size of conduit or type of cabling used at site.

IP & IK ratings for harsh environments

• Wet, dusty, wash-down: Go beyond “indoor-only” and specify the right IP rating (e.g., IP54 for dust-splash, IP65/IP66 for water jets). IP is defined by IEC 60529. IEC

• High traffic or exposed impact: In loading bays, plant corridors, or food facilities with trolley strikes, use enclosures/back boxes (or surface housings) with IK ratings—IK08 (~5 J) to IK10 (20 J) are common targets. IK ratings are defined by IEC 62262.

Hazardous areas (Zone 0/1/2; dust Zones 20/21/22)

If your installation is in a classified hazardous area, ordinary back boxes/enclosures are not acceptable. Electrical box will have to be UL explosion proof certified or ATEX certified. Explosion proof back boxes will have added safety requirements that are required in hazardous environments. 

Duallite Electric Pte Ltd supplies the industrial and commercial market with genuine RACO® (a Hubbell brand) back boxes and matching accessories. As a dedicated stockist/distributor in Singapore, we combine ready local inventory with expert product support—helping contractors and consultants specify the right box depth, knockout options, and mounting hardware for tough environments. From plant upgrades to new-build projects, we streamline submittals, cross-reference equivalent parts, and coordinate deliveries to meet site schedules. If you need dependable back boxes, rings, covers, and fittings for fast, compliant installs, talk to the Duallite Electric team.