MDB, SDB and motor control panels: Q&A, specs and starting prices

What is the difference between an MDB and a motor control panel (MCC)?

An MDB (Main Distribution Board) is the main panel that takes power from the transformer or utility meter and distributes it to the sub-panels in a building. It holds the main breaker, a power meter and a breaker for each circuit.

A motor control panel (MCC) starts, stops and protects motors such as water pumps, fans and aerators. Inside are contactors, overloads, phase protection relays and control switches.

Most of the panels we build are MCCs for clean water, wastewater and stormwater systems, as well as building automation systems. We use standard components and tidy wiring for safe operation.

• MDBDistributes the building's main supply, splits circuits, meters energy use
• MCCRuns and protects motors, pumps, fans and other equipment

DOL, star-delta or inverter: which motor starter should I choose?

It depends on the motor size and how it is used. This is our rule of thumb, which we then confirm on site.

Float switch or level sensor: which is better for pump control?

Electric float switches suit sumps, water tanks and ordinary wastewater pits. They are cheap, easy to repair and site staff can replace them. The pump starts and stops at the levels you set.

If you want to see the water level as a number, check it on your phone, or let a PLC act on several levels, we recommend a 4-20mA or RS-485 level sensor wired to a PLC, which can later be extended to online monitoring.

Our pump control panels are designed to work with both float switches and sensors, and include an alternating function to extend the life of the pumps.

Indoor / Outdoor control panels: what is the difference?

Indoor panels focus on cooling, dust and insect protection, and preventing accidental contact with live circuits. Outdoor panels are designed to withstand sun, rain and water ingress. If the panel is outdoors and exposed to rain, we recommend a roofed or double-door enclosure to prevent water pooling and long-term leakage. For very humid or chemical environments, or where extra durability is needed, we recommend stainless steel.

We design and select enclosures to suit the site, using popular brands such as Denco, Tamco, BAV and KJL. We use a hydraulic punch to cut holes for lights and switches, leaving a smooth finish with no metal burrs that could damage the seals. For special sizes we order from a factory that can laser-cut holes to your specifications.

• Indoor enclosures Indoors and pump rooms: dust and splash protection
• Outdoor enclosures Outdoors, Water treatment area, on rooftops
• Stainless steel Damp or chemical areas, such as wastewater treatment

Why does my panel trip, the pump not run, or the motor overload?

The causes we see most often are: the pump bearings are stuck or drawing too much current, low voltage or a missing phase, moisture inside the panel causing terminals to rust, and components wearing out with age. Panels without a phase protection relay are more likely to damage the motor. Another common cause of motor and magnetic breaker failure is resetting the overload and continuing to run the pump without finding the cause first.

We repair and troubleshoot existing panels, including those built by others. We check the wiring, improve the circuit, replace components and repaint the panel so it works normally and safely again.

Why does a control panel use so many wire colours, and which standard do they follow?

Different wire colours tell the different lines and circuits apart, prevent wires from being connected the wrong way round, and help electricians work safely. Today, wire colours follow the international IEC standard (and the new Thai TIS standard).

We use wire colours according to IEC 60204-1, as follows:

• ●Black AC and DC power circuits
• ●Red AC control circuits
• ●Blue DC control circuits
• ●Orange External circuits that are not switched off from inside the panel