Why Are There Hot Spots in an Electrical Panel? Thermal Inspection Guide Malaysia
Meta Description: Learn what causes electrical-panel hot spots and how thermal cameras and clamp meters help Malaysian factories investigate loose connections, overload and phase imbalance.
A hot spot inside an electrical panel means one component or connection is operating at a higher temperature than surrounding components.
Possible causes include loose connections, excessive current, phase imbalance, component deterioration, corrosion or poor ventilation.
Thermal imaging helps locate the abnormal area, but the image alone does not confirm the cause. Electrical load, component type and operating conditions must also be checked.
Common Causes of Electrical Panel Hot Spots
The most common causes include:
Loose cable connection
High-resistance joint
Circuit overloading
Uneven phase loading
Ageing circuit breaker or contactor
Corrosion or contamination
Undersized conductor
Poor panel ventilation
Failed cooling fan
High ambient temperature
1. Loose Electrical Connection
A loose connection can create additional electrical resistance.
As current passes through the resistance, heat is produced.
Possible locations include:
Cable terminals
Circuit breakers
Contactors
Fuses
Busbar joints
Motor starters
Terminal blocks
Transformer connections
A thermal camera may show a small, concentrated hot area at the connection.
Electrical connections must only be inspected or corrected by qualified personnel under the approved isolation procedure.
2. High-Resistance Joint
High resistance may develop because of:
Loose fastener
Corrosion
Oxidation
Damaged conductor
Poor crimp
Incorrect termination
Contamination
Repeated heating
The component can become hot even when current is not unusually high.
Compare the suspected connection with similar connections carrying comparable loads.
3. Circuit Overloading
An overloaded circuit may cause the complete conductor, breaker or component to become warmer.
Possible causes include:
Additional machinery
Increased production load
Incorrect circuit design
Undersized component
Mechanical overload on a motor
Changed operating condition
Use a clamp meter to measure actual current.
Compare it with:
Component rating
Cable capacity
Motor nameplate
Previous readings
Similar circuits
Actual equipment load
4. Uneven Phase Loading
In a three-phase panel, one phase may carry more current than the others.
This can cause one phase conductor or breaker pole to appear hotter.
Measure:
L1 current
L2 current
L3 current
Phase-to-phase voltage
Equipment load
A temperature difference may be caused by unequal current rather than a loose connection.
5. Voltage Imbalance
Voltage imbalance can contribute to current imbalance and motor heating.
Qualified personnel should check all phase-to-phase voltages using a suitable digital multimeter.
Voltage, current and thermal information should be evaluated together.
6. Ageing Circuit Breaker
A circuit breaker may develop internal resistance because of:
Ageing contacts
Repeated operation
Previous fault current
Mechanical wear
Contamination
Heat damage
A breaker may appear hotter than similar breakers even at a comparable load.
Do not assume that tightening the external terminal will correct an internal breaker problem.
7. Contactor Problems
Contactors switch motors and industrial equipment repeatedly.
Possible issues include:
Worn contacts
Coil problems
Loose terminals
Contamination
Mechanical wear
High operating frequency
Thermal imaging may reveal uneven temperature between poles or abnormal heating around the coil or terminals.
8. Fuse Heating
A fuse or fuse holder may become hot because of:
High current
Poor contact
Corrosion
Incorrect fuse selection
Damaged holder
Loose connection
Compare the fuse assembly with similar phases and check actual current.
9. Corrosion and Contamination
Factories may expose electrical panels to:
Humidity
Chemical vapour
Dust
Oil mist
Water leakage
Condensation
Contamination can increase resistance and reduce cooling.
Inspect:
Door seals
Cable entries
Ventilation filters
Terminal condition
Panel roof
Nearby water pipes
10. Poor Panel Ventilation
The complete panel may become hot because of:
Blocked vents
Dirty filters
Failed fan
Incorrect fan direction
High internal load
Closed cooling path
Nearby heat source
Use:
Temperature data logger
Anemometer
Thermal imaging camera
Infrared thermometer
Check both component hot spots and overall enclosure temperature.
11. High Ambient Temperature
A panel installed in a boiler room, compressor room or hot production area may operate at a higher temperature.
Record:
Room temperature
Panel internal temperature
Production load
Time of day
Ventilation status
A data logger helps determine whether the problem occurs only during certain periods.
Localised Hot Spot vs General Heating
Localised Hot Spot
May indicate:
Loose connection
Corrosion
Damaged termination
Internal component resistance
Poor contact
General Heating
May indicate:
Overloading
High ambient temperature
Poor ventilation
Multiple heat-producing components
Incorrect enclosure design
The heat pattern helps determine the direction of investigation.
Why Electrical Load Must Be Recorded
Temperature depends partly on current.
A connection carrying little current may not show a clear hot spot even when resistance is present.
A heavily loaded but healthy component may appear warmer than an unloaded component.
Always record:
Current
Equipment status
Production load
Ambient temperature
Inspection time
How to Perform a Basic Thermal Inspection
Step 1: Identify the Panel
Record the panel name, circuit and connected equipment.
Step 2: Confirm Operating Load
The equipment should be under a known operating condition.
Step 3: Scan the Complete Panel
Inspect breakers, contactors, terminals, busbars and cable connections.
Step 4: Compare Similar Components
Compare phases and similar devices under comparable loads.
Step 5: Save the Thermal Image
Record the component, temperature pattern, date and load.
Step 6: Measure Current
Use a suitable clamp meter to check phase and circuit current.
Step 7: Arrange Further Investigation
Qualified personnel should assess abnormal findings and determine the corrective action.
Thermal Camera vs Infrared Thermometer
FeatureThermal Imaging CameraInfrared ThermometerInspection areaComplete temperature imageOne selected spotUnknown hot-spot locationEasier to findMay be missedPanel scanningHighly suitableLimitedDocumentationThermal imageIndividual readingRoutine known-point checkSuitableSuitable and economical
A thermal camera is generally the better tool for locating unknown electrical hot spots.
Choosing Thermal Resolution
Higher thermal resolution generally provides:
More image detail
Better identification of small components
Improved inspection from a greater distance
Clearer maintenance records
MTM Precision offers Wintact thermal cameras including:
ModelThermal ResolutionWintact WT3090120 × 90Wintact WT3160160 × 120Wintact WT3220220 × 160Wintact WT3320320 × 240
The suitable resolution depends on component size, inspection distance, reporting needs and budget.
Useful Electrical Panel Inspection Tools
What to CheckRecommended InstrumentUnknown hot spotsThermal imaging cameraKnown surface-temperature pointInfrared thermometerLoad currentClamp meterVoltageDigital multimeterInsulation conditionInsulation resistance testerPhase sequencePhase sequence meterPanel temperature over timeTemperature data loggerCooling airflowAnemometer
Common Thermal Inspection Mistakes
Avoid:
Inspecting without recording current
Comparing loaded and unloaded phases
Ignoring emissivity and reflections
Measuring shiny metal incorrectly
Looking only at the hottest point
Ignoring ambient temperature
Assuming every hot component is overloaded
Assuming every hot terminal is loose
Using an infrared thermometer without knowing where to aim
Opening live panels without authorisation
Approaching exposed conductors without suitable PPE
Correcting the symptom without investigating the cause
Important Electrical Safety Reminder
Thermal imaging is non-contact, but opening or approaching an energised electrical panel may expose the operator to electric shock and arc-flash hazards.
Inspection should only be performed by authorised personnel following:
Site electrical-safety procedures
Appropriate PPE requirements
Safe approach distances
Permit and authorisation requirements
Instrument limitations
Approved corrective-work procedures
Electrical Thermal Inspection Tools Supplier in Malaysia
MTM Precision supplies instruments for identifying electrical-panel hot spots, motor overloading, phase-current differences, abnormal terminal temperature and ventilation problems.
Our range includes Wintact thermal imaging cameras, Smart Sensor AR600E infrared thermometers, clamp meters, digital multimeters, insulation resistance testers and temperature data loggers.
Contact MTM Precision
MTM Precision Sdn. Bhd.
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
🌐 Website: www.mtmpre.com.my
📧 Email: mtmpre@yahoo.com
📱 WhatsApp: +6016-660 7346
31 Aug 2026
