LV Power Switchboards: IEC 61439 Design Verification and Assembly Data

A procurement and engineering guide for low-voltage power switchboards covering temperature rise, short-circuit withstand, internal separation, RDF, IP and rout

1. Apply the Correct Assembly Part

IEC 61439-1:2020 gives the general rules, service conditions, construction requirements, technical characteristics and verification requirements for low-voltage assemblies. IEC 61439-2:2020 gives the specific requirements for power switchgear and controlgear assemblies up to 1,000 V AC or 1,500 V DC.

IEC 61439-1 is not a stand-alone conformity route. The relevant product part, assembly manufacturer responsibility and verified reference design must be identified in the enquiry.

2. Design Verification Matrix

Verification areaData to lock before manufacture
Temperature riseRated current, group rated current, ambient, enclosure, ventilation and rated diversity factor
Short circuitIcw duration, Ipk, protective-device limitation and busbar/joint arrangement
InsulationRated insulation voltage, impulse withstand, clearances, creepage and pollution environment
Protection and serviceIP, internal separation form, earthing, neutral, EMC, arc path and maintenance method

The assembly manufacturer must keep the verification tied to the actual busbar, functional-unit, enclosure and cooling construction. Importing a breaker rating does not verify the complete panel.

3. Nameplate and One-Line Consistency

The single-line must identify incomers, bus couplers, outgoing circuits, neutral arrangement, protective devices, control voltage, measurement and spare ways. The panel schedule must retain the same circuit names and loading assumptions used for temperature-rise and short-circuit verification.

Distinguish the breaker’s Icu/Ics from the assembly’s Icw/Ipk. Also distinguish the rated current of a functional unit from the group rated current and from the actual project load.

4. Routine Verification and Handover

  • Check workmanship, protective conductor continuity, clearances, creepage, mechanical operation, interlocks and labeling.
  • Verify wiring, insulation, dielectric or functional checks required by the applicable assembly part.
  • Record torque, protective-device settings, test instruments, revision-controlled drawings and the exact verified configuration.
  • Do not accept a generic “type-tested panel” statement without the reference design, deviations and the project’s actual assembly data.

*Reference: IEC 61439-1:2020; IEC 61439-2:2020; IEC 61439-6:2012.*