MCC Panels
Main Distribution Board
Custom Main Distribution Board for low-voltage power receiving, main protection, metering, and feeder distribution. Built for commercial and industrial projects with configurable incomer, busbar rating, outgoing circuits, cable entry, and documentation for safer procurement decisions.
Custom Low Voltage Main Distribution Board for Commercial, Industrial, and Utility Power Distribution
A main distribution board, also called an MDB or main distribution panel board, is the primary low-voltage power distribution point after the transformer, generator, or utility incoming supply. It distributes power to sub main distribution boards, MCC panels, lighting panels, HVAC loads, pumps, production lines, and other downstream electrical systems.
Uniregal builds customized main distribution boards for projects that require clear feeder arrangement, reliable main protection, safe isolation, metering, and future expansion space.
What Is a Main Distribution Board?
A main distribution board is the main electrical assembly that receives incoming low-voltage power and distributes it to multiple outgoing feeders.
In a typical electrical system:
Transformer / Generator / Utility Supply → Main Distribution Board → SMDB / MCC / DB / Load Panels → Equipment
The MDB is normally responsible for:
- Main incoming isolation
- Short-circuit and overload protection
- Power distribution to downstream panels
- Busbar power transfer
- Energy metering and monitoring
- Surge protection
- Earthing and neutral arrangement
- Feeder protection and cable termination
Why MDB Selection Matters
An MDB is not a small branch panel. If it is undersized or poorly designed, the problem affects the whole facility.
A wrong MDB specification can cause the following:
- Main breaker nuisance tripping
- Cable termination problems on site
- Insufficient short-circuit withstand rating
- Poor selectivity between main and downstream breakers
- Overheating inside the enclosure
- No spare outgoing feeders for future expansion
- Confusion between normal power and emergency power circuits
- Failed consultant approval due to incomplete drawings or missing test data
Buyer Decision Information
Before purchasing a main distribution board, confirm these points first.
Decision Item | Why It Matters | Buyer Should Confirm |
|---|---|---|
Incoming power source | MDB design changes depending on transformer, generator, ATS, or utility supply | Voltage, phase, frequency, source quantity |
Main incomer rating | Determines the main switch, MCCB/ACB, busbar, and enclosure size | Rated current, breaking capacity, poles |
Short-circuit rating | A low-rated MDB may be unsafe even if the current rating looks correct | Available fault current at MDB location |
Busbar material | Impacts temperature rise, cost, and long-term reliability | Copper or aluminum, rated current, neutral size |
Outgoing feeder schedule | The MDB must match real downstream loads | Quantity, rating, breaker type, cable size |
Selective coordination | Prevents the whole MDB from tripping for a downstream fault | Breaker curves, cascading, discrimination |
Cable entry direction | Affects installation, bending space, gland plate, and site labor | Top entry, bottom entry, front/rear access |
Metering requirement | Some projects need tenant, energy, power quality, or BMS data | Multifunction meter, CT ratio, communication |
Emergency load separation | Essential loads should not be mixed casually with normal loads | Emergency MDB, ATS, generator feeders |
Expansion capacity | Future feeders are cheaper to reserve during manufacturing | Spare ways, spare busbar space, blank compartments |
Main Distribution Board vs Other Panels
Product | Main Function | Buyer Should Not Confuse It With MDB Because |
|---|---|---|
Main Distribution Board | Main low-voltage power receiving and distribution | It is the upstream distribution point for the facility |
Sub Main Distribution Board | Distributes power to a building zone, floor, workshop, or area | It is downstream of the MDB |
Distribution Board | Feeds final branch circuits such as lighting or small power | Usually lower current and closer to final loads |
MCC Panel | Controls multiple motors | Focus is motor starting, protection, and control, not general power distribution |
Power Control Panel | Controls or distributes power for a specific machine/system | It may not serve as the facility’s main distribution point |
Main Switchboard | Often used for larger service entrance or switchboard assemblies | In some markets, MDB and switchboard overlap, but standards and construction may differ |
Key Specifications for Main Distribution Board
Parameter | Common Options |
|---|---|
Product Name | Main Distribution Board / MDB / Main Distribution Panel Board |
Rated Voltage | 220V / 380V / 400V / 415V / 480V / Customized |
Phase | Single-phase / Three-phase |
Rated Current | Customized according to load schedule |
Main Incomer | MCCB / ACB / Switch Disconnector / Fuse Switch |
Outgoing Feeders | MCCB / MCB / Fuse Switch / Isolator |
Busbar | Copper / Aluminum |
Enclosure | Floor-standing / Wall-mounted / Modular cubicle |
Installation | Indoor / Outdoor |
Protection Level | IP rating based on site environment |
Cable Entry | Top / Bottom / Customized |
Metering | Voltmeter, ammeter, multifunction meter, energy meter |
Protection Devices | Overload, short-circuit, earth fault, surge protection optional |
Standards | IEC 61439 or project-required local standard |
Application | Factory, commercial building, plant room, utility room, infrastructure, water treatment, HVAC system, production facility |
Main Switch and Incomer Options
The main switch is one of the most important MDB decisions.
Typical options include the following:
- MCCB incomer for medium-current MDB applications
- ACB incomer for higher-current systems or projects needing advanced protection
- Switch disconnector when upstream protection is already provided
- Fuse switch where fused protection is preferred
- ATS incomer when normal and generator power changeover is required
Buyer tip: do not only ask for “main switch distribution board.” Confirm whether you need isolation only, overload protection, short-circuit protection, earth fault protection, or automatic transfer.
Outgoing Feeder Design
The outgoing feeder arrangement should be based on the actual downstream load schedule.
Common outgoing feeders include:
- SMDB feeders
- MCC panel feeders
- HVAC panel feeders
- Pump panel feeders
- Lighting distribution panel feeders
- Production line feeders
- Utility and plant room feeders
- Spare feeders for future expansion
For each feeder, confirm:
- Load name
- Rated current
- Cable size
- Breaker type
- Number of poles
- Trip setting requirement
- Whether metering or status signal is needed
Emergency Main Distribution Board
An emergency main distribution board is used when essential loads must remain powered during normal supply failure.
Typical emergency loads include the following:
- Fire pump systems
- Emergency lighting
- Smoke extraction fans
- Critical ventilation
- Security systems
- Essential process loads
- Control room power
Buyer warning: emergency feeders should be clearly separated from normal distribution. If the project includes generator power or ATS, this must be shown in the single-line diagram before manufacturing.
MDB Symbol and Drawings
For engineering approval, the MDB should not be treated as only a product photo. Buyers usually need proper electrical documentation.
Recommended documents include:
- Single-line diagram
- General arrangement drawing
- Main distribution board symbol on layout drawings
- Breaker schedule
- Busbar rating
- Cable entry drawing
- Terminal and gland plate layout
- Metering and CT wiring diagram
- Nameplate list
- Test report
- Packing list
Common Components Inside an MDB
A custom MDB may include:
- Main circuit breaker or switch disconnector
- Copper or aluminum busbar
- Outgoing MCCB/MCB/fuse switches
- Neutral bar and earth bar
- Surge protection device
- Multifunction power meter
- Current transformers
- Indicator lamps
- Control power transformer
- Door interlock
- Cable gland plate
- Ventilation or anti-condensation heater
- Internal barriers and shrouds
- Labels and warning signs
Common Buying Mistakes to Avoid
Mistake 1: Buying by enclosure size only
MDB cost and suitability are determined by current rating, short-circuit rating, busbar size, breaker brand, feeder quantity, and cable space. Size alone is not enough.
Mistake 2: Confusing MDB with SMDB
An MDB is upstream and feeds major downstream panels. An SMDB is a secondary distribution board for a specific floor, area, or load group.
Mistake 3: Ignoring fault level
A 400A MDB with insufficient breaking capacity can still be unsafe. Always confirm the available short-circuit current from the transformer or consultant's design.
Mistake 4: Not allowing enough cable termination space
Large incoming and outgoing cables need bending space, lug clearance, gland plate space, and installation access.
Mistake 5: No spare feeders
Adding spare feeders later is more expensive and may require shutdown. Reserve spare ways during the first build.
Mistake 6: Mixing emergency and normal loads
Emergency circuits should be planned separately, especially when generator power, ATS, or fire safety loads are involved.
Information Needed for Quotation
To quote a main distribution board accurately, please provide the following:
- Project voltage and frequency
- Single-line diagram
- Incoming breaker rating
- Short-circuit rating requirement
- Outgoing feeder list
- Preferred breaker brand
- Indoor or outdoor installation
- IP rating requirement
- Cable entry direction
- Metering requirement
- ATS or generator connection requirement
- Required standard
- Drawing approval requirement
- Quantity and delivery schedule
FAQ
What is a main distribution board?
A main distribution board is the main low-voltage electrical panel that receives incoming power and distributes it to downstream distribution boards, MCC panels, and major loads.
What does MDB mean in electrical systems?
MDB means Main Distribution Board. It is usually the main distribution point after the transformer, generator, or utility incoming supply.
What is the difference between a main distribution board and a sub-main distribution board?
The MDB is the primary distribution board. The SMDB is downstream from the MDB and distributes power to a specific area, floor, workshop, or load group.
What is the difference between a main switchboard and a distribution board?
A main switchboard is often a larger service entrance or main distribution assembly. A distribution board is generally used to distribute power to downstream or branch circuits. In some projects, the MDB and main switchboard may overlap, so the required standard and configuration should be confirmed.
What is the main switch in a distribution board?
The main switch is the incoming isolation or protection device that can disconnect the whole board from the power supply. It may be an MCCB, ACB, switch disconnector, or fuse switch.
How do I choose the correct MDB rating?
Start from the total load, diversity factor, transformer capacity, future expansion, voltage, and available short-circuit current. Do not choose the MDB only by current rating.
Can an MDB feed an MCC panel?
Yes. An MDB commonly feeds MCC panels, HVAC panels, pump panels, SMDBs, lighting panels, and other downstream electrical panels.
Can you build an ABB main distribution board?
We can build a customized MDB using ABB components if specified. The final product should be described as a custom main distribution board with ABB breakers or components, unless the complete system is supplied as an official ABB assembly.
What drawings are required before production?
A single-line diagram, general arrangement drawing, feeder schedule, cable entry layout, and breaker list are usually required before production.
What is an emergency main distribution board?
An emergency MDB distributes backup power from a generator or emergency supply to essential loads such as fire pumps, emergency lighting, smoke extraction fans, and critical control systems.
Is a home main distribution board the same as an industrial MDB?
No. A home's main distribution board is usually smaller and simpler. Industrial and commercial MDBs require higher current capacity, stronger fault protection, better cable space, metering, and project documentation.
Request a Custom MDB Quote
Send your single-line diagram, feeder schedule, voltage, current rating, and installation requirements. Uniregal can help review the specification and provide a main distribution board design suitable for your project.
Contact us through:
Email: info@uniregal.com
Web: www.uniregal.com