Infrared Thermography for MCC Inspection: Best Practices

Infrared thermography is the most effective predictive maintenance tool for motor control centers. It detects overheating connections, failing components, and load imbalances before they cause failures. This guide covers best practices for implementing a thermographic inspection program for your MCCs.

Why Thermography for MCCs

Every electrical connection in an MCC is a potential failure point. Loose connections, corroded contacts, and degraded stab assemblies all create resistance, which generates heat. By the time a connection is hot enough to smell or see damage, significant deterioration has already occurred.

Infrared thermography detects temperature differences invisible to the naked eye. A connection running 20 degrees C above ambient might look completely normal visually, but it is on a degradation path that will eventually lead to failure.

Return on Investment

A quality thermographic inspection program typically costs $500-$2,000 per MCC per year (including equipment amortization or contractor fees). A single unplanned MCC failure can cost:

• $5,000-$20,000 for emergency bucket replacement
• $10,000-$100,000+ in lost production (depending on the process)
• Potential safety incident costs (incalculable)

The ROI for thermographic inspection is typically 10:1 or better.

Equipment Requirements

Camera Specifications

For MCC inspection, the infrared camera should have:

• Resolution: Minimum 320x240 pixels (640x480 preferred)
• Sensitivity (NETD): 0.05 degrees C or better
• Accuracy: +/- 2 degrees C or +/- 2% of reading
• Temperature range: -20 degrees C to at least 350 degrees C
• Focus: Manual focus capability (autofocus can struggle in MCC environments)
• Image storage: Radiometric image capture for later analysis

Recommended Camera Brands

FLIR, Fluke, Hikvision, InfiRay, and Testo all produce suitable cameras. Mid-range models ($3,000-$10,000) are adequate for most MCC inspection programs.

Additional Equipment

• Visual camera: For reference photos alongside thermal images
• Spot thermometer: For verification of camera readings
• Flashlight: For visual inspection inside bucket compartments
• PPE: Arc-rated clothing per NFPA 70E for the MCC's incident energy level
• IR windows: If installed in MCC doors, these allow scanning without opening doors

Scanning Procedures

Pre-Scan Preparation

1. Verify load conditions: MCCs should be under at least 40% of rated load during scanning. Lightly loaded connections may not show thermal anomalies even when degraded. Schedule scans during normal production hours.

2. Review previous scan data: Compare current conditions to historical baselines to identify trends.

3. Confirm access: Ensure all MCC sections are accessible. Clear any obstructions in front of the MCC.

4. PPE assessment: Determine the arc flash incident energy for each MCC section. Don appropriate PPE per NFPA 70E before opening any doors or panels.

Scanning Technique

Through IR Windows (Preferred) If IR windows are installed in MCC doors:

1. Clean the IR window lens surface
2. Position the camera perpendicular to the window
3. Focus through the window on the internal components
4. Capture radiometric images of each bucket

With Doors Open (Standard) If no IR windows are installed:

1. Follow NFPA 70E requirements for opening energized panels
2. Wear appropriate arc flash PPE
3. Open bucket doors one section at a time
4. Scan from top to bottom, left to right systematically
5. Focus on connection points: stab area, breaker terminals, contactor terminals, overload connections, wire terminals

External Scan (Supplementary) Scan the MCC exterior even with doors closed:

• Bus connection compartments (top of sections)
• Incoming cable connections
• External surfaces that may show internal heating

What to Focus On

Prioritize these connection points during scanning:

1. Stab connections: Where buckets meet the vertical bus
2. Breaker/fuse connections: Power input and output terminals
3. Contactor connections: Line side and load side
4. Overload relay connections: Through current paths
5. Control transformer: Primary and secondary connections
6. Terminal blocks: All power and control terminals
7. Bus connections: Horizontal-to-vertical bus joints
8. Cable connections: Where feeder cables terminate

Interpreting Results

Temperature Criteria

Based on NETA MTS (Maintenance Testing Specifications) and industry best practices:

Delta-T (Above Reference)	Priority	Action
1-10 degrees C	Low	Monitor at next scheduled scan
11-20 degrees C	Medium	Schedule repair within 1-3 months
21-40 degrees C	High	Repair within 1-2 weeks
Over 40 degrees C	Critical	Immediate action required

Reference temperature is typically the temperature of an adjacent similar connection under similar load. Phase-to-phase comparison on the same bucket is the most reliable reference.

Common Findings

Hot Stab Connection: One phase of a bucket's stab connection is significantly hotter than the other two phases. Indicates degraded stab contact on that phase. Solution: clean or replace stab assembly.

Hot Breaker Terminal: One terminal of the breaker is hotter than others. Usually a loose connection. Solution: retorque the connection.

Hot Contactor Terminal: Similar to breaker terminal. Loose connection or degraded contact. Solution: retorque or replace contactor.

Overall Bucket Hot: All connections in one bucket are elevated compared to similar buckets. May indicate the bucket is overloaded or has poor ventilation. Verify load against bucket rating.

Bus Connection Hot: Elevated temperature at the horizontal-to-vertical bus connection. Indicates a loose or corroded bus joint. Solution: de-energize, clean, and retorque the connection.

Reporting and Documentation

Report Contents

• Date, time, and ambient conditions
• MCC identification (location, manufacturer, model)
• Load conditions during scan
• Thermal images with temperature annotations
• Reference temperatures for comparison
• Severity classification for each finding
• Recommended actions and priority
• Comparison to previous scan results (if available)

Trending

Maintain a database of all thermographic findings. Track temperatures over time to identify degrading connections before they reach critical levels. A connection that was 5 degrees C elevated last year and 12 degrees C elevated this year is trending toward failure.

Scan Frequency

MCC Criticality	Recommended Frequency
Critical process MCCs	Quarterly
Important production MCCs	Semi-annually
General purpose MCCs	Annually
Low-priority MCCs	Every 2 years

Increase frequency for older MCCs (20+ years) and MCCs in harsh environments.

Need Help with MCC Maintenance?

When thermographic inspections reveal degraded buckets, MCC Depot provides fast replacement buckets and field services for all major brands.

Call 307-442-0382 or email sales@mccdepot.com for emergency and scheduled bucket replacements.