After the LT panel, power still has to reach every floor, room and machine. That is the job of the distribution boards: the MDB, DBs and SDBs. Planned well, they make a building safe, easy to maintain and easy to expand.
What is an MDB panel?
Our ebook describes the MDB (Main Distribution Board) as a panel or enclosure that houses the fuses, circuit breakers and ground leakage protection units where the electrical energy used to distribute power to many individual circuits or consumer points is taken in from the transformer or an upstream panel.
In a building with its own substation, the MDB is often the LT panel itself or the first board after it. In a building fed directly from the utility at 415 V, the MDB is the main incoming board.
DB and SDB panels
- DB (Distribution Board): fed from the MDB, it serves one floor, one section of a factory or one large area.
- SDB (Sub-Distribution Board): fed from a DB, it serves a smaller area such as a flat, an office suite or a group of machines.
Together they form a tree: transformer → LT panel → MDB → DB → SDB → final circuits. See our DB and SDB panel page.
What goes inside
| Board | Typical incomer | Typical outgoing devices |
|---|---|---|
| MDB | ACB or large MCCB | MCCBs for each DB or large load |
| DB | MCCB | MCCBs or MCBs |
| SDB | MCB or small MCCB | MCBs and RCCB / earth leakage protection |
Every board should also have proper neutral and earth bars, clear labelling and enough spare ways for future circuits.
Planning tips for safe distribution
- Discrimination: choose breaker ratings so that a fault trips only the nearest breaker, not the whole building.
- Earth leakage protection: use RCCBs or ELCBs where people can touch equipment, such as offices, flats and wet areas.
- Load balance: share single-phase loads evenly across the three phases.
- Spare capacity: leave about 20% spare ways and rating for future growth.
- Location: keep boards accessible, dry and away from water lines.
- Standards: follow BNBC and IEC, and Accord–Alliance requirements in RMG factories.
Frequently asked questions
What is the difference between an MDB and an LT panel?
The LT panel takes power directly from the transformer. The MDB distributes power to the building’s DBs. In smaller buildings one panel may do both jobs.
Can you supply MDBs with branded breakers?
Yes. We build MDBs, DBs and SDBs with genuine ABB, Schneider Electric, Siemens, Mitsubishi and Fuji Electric breakers — see our guide to ACB, MCCB and MCB.
Get a distribution board quotation
Send us your building’s SLD or a list of floors and loads. See our MDB panel page or request a quotation.
বাংলায় পড়ুন: এমডিবি, ডিবি ও এসডিবি প্যানেল: ভবনের ভেতরে বিদ্যুৎ কীভাবে বণ্টন হয়
