Sub Main Distribution Board (SMDB) – also known as a sub main panel—acts as the intermediate link between the Main Distribution Board (MDB) and the final consumer units or equipment.
Sub Main Distribution Boards (SMDBs) are governed by the same international standards as Main Distribution Boards: the IEC 61439 series.
- IEC 61439-2 (Power Switchgear and Controlgear Assemblies): This is the most common standard for SMDBs in industrial and commercial environments. It applies to panels operated by “instructed or skilled persons” and covers high-performance requirements like short-circuit withstand and temperature rise.
- Internal Separation: Often specified as Form 2b for sub-panels to isolate busbars from functional units, enhancing safety.