A lot can go wrong with this vital equipment. Here’s expert advice on managing your MCC.

Key Takeaways:

  • Power loss, motor overloading, and relay malfunctions are common and troublesome issues.
  • MCC designs share common components that may cause problems.
  • Maintaining your MCC minimizes downtime and ensures smoother system operation.

Motor control centers (MCCs) are responsible for controlling the speed, direction, and performance of electrical motors essential to the function of sitewide systems like HVAC and server rooms. MCCs are also sensitive and complex collections of hardware prone to various performance issues.

MCCs offer varied designs, which increase the variety of things that can go wrong. A combination of the manufacturer’s manual and strict guidelines from the International Electrical Testing Association sets the standard for how well MCCs should function. This is why only qualified electricians should attempt to diagnose and repair motor MCC problems. Here’s how we do it!

The two MCC classes 

MCCs feature low- or medium-voltage designs. The first type handles voltages upwards of 230V but below 1,000V and are used for AC three-phase motors (where three separate conductors transmit electricity rather than one). Medium-voltage MCCs house bigger motors operating in the 1,000  to 15,000V range.

Knowing a unit’s voltage is very important when troubleshooting. What constitutes overcurrent – a key metric in diagnosing MCC issues – becomes relative. Other design differences include whether the MCC uses fuses or circuit breakers to deal with overcurrent, and if the motors start using variable frequency drives or run at a constant speed via direct-line connections.

Electrical teams must be able to assess the kind of MCC they’re working on. Once they have, they’ll probably find one or more common problems.

Preventing power loss

The best troubleshooting manages risks before problems occur. A big MCC complaint is power loss through overloading and overcurrent often caused by grid outages or power surges. Electrical professionals can sometimes identify damage caused by either problem with an inspection. Loose wires, tripped indicators, or burnt-out components are easy to spot.

Electricians troubleshoot using specialized tools (more on those below). Businesses can protect their MCC against outages and surges by installing the right commercial generator and surge protection devices (SPDs). Generators help keep your MCC running during blackouts while SPDs can protect sensitive motor control parts from overloads and overcurrent.

SPDs can include power strips with built-in surge protection, or heavy-duty surge suppressors fitted to business’ main service panels to withstand bigger surges and ease the strain on weaker SPDs. Combining generators and SPDs with an uninterruptible power supply (UPS) provides triple-tiered MCC protection.

More MCC troubleshooting tips

Electricians will power down the MCC and disengage motors before checking them for mobility issues and looking for warning signs. For example, all MCC motors must be able to rotate freely. Any lag or obstruction will impede performance and/or cause wider damage. These are among the first things professionals look for.

Next, they’ll do a “senses check” on the MCC. An expert’s eyes and ears can often pinpoint trouble without tools. Inspection of fuses, voltages, and resistance levels might reveal loose wire nuts or poorly insulated motor connections.

Megohmmeters and voltmeters are tools used to test insulation resistance and voltage, respectively. Resistance tests check how effectively the MCC is grounded, and how well fuses and motor load lines function. Voltmeters check for voltage imbalances which might be due to excessive current or low motor torque.

Blown fuses are another MCC problem; they need replacement. Fuses may become loose; they’re fixed into spring-loaded tensile holders that keep fuses in position. When these lose tension, the fuse can’t make necessary contact. Fixtures may need repositioning or replacement.

Some situations require infrared thermography equipment which lets electricians investigate MCCs while running at full loads to identify potential overheating. If this is the issue, cleaning, replacing, or upgrading components enables cooling.

Dealing with moisture and other messes

Dust and grime can impede MCC performance; remove it with a soft cloth or a gentle vacuum. Condensation and moisture can trigger leaks and subsequent MCC problems. Rust on an MCC is usually a sign of moisture.

Businesses must carefully monitor the temperature and humidity with electrical equipment that minimizes condensation and ensures the room is free of leaks. The room can’t be too hot or too cold; two site-specific factors dictate the “right” temperature: the MCC’s specified safe operating temperature of the MCC itself, and the size of its room. This reveals the heat load generated and, by extension, how cool the room must be.

MCC moisture can be mitigated when the unit is properly sealed during installation. Failing that, an electrician will have to eliminate moisture and repair or replace water-damaged components before sealing it tightly. They’ll also check for water entry points. Some structural repairs may be beyond the electrician’s job description, so take any recommendations for secondary work seriously!

Call UES for MCC troubleshooting tips and maintenance

Diligent care and routine maintenance can prevent trouble before it starts. Trust this kind of maintenance to the experts. Untrained tinkering could worsen existing issues or cause new ones, or even injure people. Professionals can inspect your MCC safely. Contact us if you’re having problems. We offer a free quote to help you keep your equipment in good working order!