Published · Vili Power Solutions
Safety first
Everything in the first list can be noticed from the outside of the equipment. Opening MCC buckets, removing covers, or racking units in and out is for qualified people using lockout/tagout and the protective equipment shown on the arc flash label. An MCC can deliver a severe arc flash even when it looks quiet.
Signs you can spot from the outside
- Heat. Doors or sections that are noticeably warmer than the rest of the lineup, a room that has gotten hotter over the years, or ventilation openings blocked by dust or stored material.
- Discoloration and smell. Browned paint or labels around a bucket, or a hot plastic or burning smell near the lineup.
- Noise. Contactors that chatter or buzz loudly, or a hum that is louder than it used to be.
- Nuisance trips. Overloads or breakers that trip without a clear reason, especially on starters that have run fine for years.
- Buckets that fight back. Units that are hard to rack, handles that do not operate cleanly, or doors that will not latch.
- Dust, moisture, and corrosion. Buildup on and around the lineup, water stains from roof leaks or wash-down, and corrosion from ammonia or hydrogen sulfide in dairies and digesters.
- Missing information. No current drawings, buckets labeled for equipment that was removed years ago, and no arc flash labels.
What the problems usually turn out to be
- Loose and overheated connections at stabs, line and load terminals, and bus joints. Heat makes them looser over time, and eventually something fails.
- Worn contactors and overloads that have cycled hundreds of thousands of times, with pitted contacts and overload settings that no longer match the motor.
- Motors that changed without the starter changing with them, leaving the overload or the fuse wrong for the load.
- Contamination. Dust and moisture on insulators and bus that can track and flash over.
- Obsolete parts. Lineups that are thirty or forty years old where replacement buckets and components are no longer made, so every failure turns into a search for used parts.
Maintenance that pays for itself
Most MCC failures give warning, and a maintenance program is how you hear it. NFPA 70B, the industry standard for electrical equipment maintenance, lays out the approach. In practice, for most plants and dairies, it comes down to a few things:
- A thermal scan once a year with the equipment running under normal load. Infrared imaging finds hot connections before they fail and gives you a list to fix during a planned shutdown.
- A planned de-energized inspection every few years: cleaning, torque checks on connections, inspecting stabs and contacts, and verifying overload settings against motor nameplates.
- Housekeeping. Keeping the room clean, dry, ventilated, and clear of storage.
- Updated drawings and labels so the next person, at two in the morning, knows which bucket feeds which motor.
Repair, retrofit, or replace
An old MCC is not automatically a replacement. If the structure and bus are sound, individual buckets can often be rebuilt or replaced with modern units that fit the existing sections, and drives or soft starters can be added where motors need them. When the bus is damaged, the parts are gone, or the lineup no longer has room for what the plant needs, replacing it in planned stages during scheduled shutdowns keeps downtime to a minimum. Our motor control center services page covers that work in more detail, and the tripping motor or drive checklist helps when a single starter is the problem.
When to call
Call right away for burning smells, visible scorching, or a bucket that trips and will not reset. Call soon for repeated nuisance trips, chattering contactors, or a lineup that has not been looked at in years. We inspect, thermal-scan, repair, and retrofit motor control centers for plants, dairies, and digesters across Northern Colorado. Contact us or call (970) 685-2068.
