There is no single maximum electrical panel temperature that determines whether industrial switchgear, MCCs, or panelboards are overheating. Temperature rise, or ΔT, is more useful. Under NETA guidance, a connection more than 15°C (27°F) hotter than a similar component under similar load, or more than 40°C (72°F) above ambient, is a major discrepancy requiring immediate repair.
A thermography report on your switchgear or MCCs lands on your desk with a dozen highlighted hot spots. One connection is 8°C warmer than the one beside it. Another is 25°C above ambient. Which one actually needs attention first?
The answer is not simply whichever component has the highest absolute temperature. Electrical equipment normally generates heat under load, so determining whether a reading is concerning requires context. What matters is how much hotter a connection is running than it should under comparable conditions.
Electrical panels, breakers, switchgear, and motor control centers generate heat while carrying current. A component feeling warm does not automatically mean something is wrong.
Most low-voltage electrical equipment is designed around a maximum ambient temperature of approximately 40°C (104°F), but that does not mean every component inside the enclosure should stay below 40°C. Conductors and terminations have their own temperature ratings, and the equipment configuration and applicable rating determine allowable operating conditions.
That is why an absolute temperature by itself can be misleading. A connection operating at 50°C (122°F) in a 35°C (95°F) environment tells a different story than the same connection temperature in a much cooler environment.
For residential panels that are hot to the touch, smell like burning material, or are buzzing, contact a licensed electrician.
ΔT, or temperature rise, is the difference between the temperature at the monitored connection and a reference temperature. That reference can be ambient air or, preferably, a similar component operating under similar load.
Comparing similar components can make abnormalities easier to identify. If three comparable phase connections are carrying similar loads but one is significantly hotter than the others, that difference can point maintenance teams toward a developing problem even when the absolute temperature does not initially look extreme.
Load matters too. An infrared scan performed while equipment is lightly loaded may produce a much different reading than a scan performed during normal operating conditions. The same temperature reading can therefore mean different things depending on ambient temperature, equipment load, and what comparable components are doing at the same time.
Temperature rise gives maintenance teams a more useful question to ask: How abnormal is this connection compared with what it should be doing right now?
If you are looking at a thermography report right now, the temperature difference can help determine the severity of the finding.
ANSI/NETA MTS Table 100.18 provides guidance for evaluating temperature differences found during thermographic inspections. When available, comparison with a similar component under similar load is the more reliable method.
NETA Table 100.18 Thermography Severity Guidance
| Level | Rise vs. Similar Component | Rise vs. Ambient | Recommended Action |
|---|---|---|---|
| 1 | 1–3°C (2–5°F) | 1–10°C (2–18°F) | Possible deficiency, warrants investigation |
| 2 | 4–15°C (7–27°F) | 11–20°C (20–36°F) | Probable deficiency, repair as time permits |
| 3 | Not specified | 21–40°C (38–72°F) | Monitor until corrective measures can be taken |
| 4 | Over 15°C (27°F) | Over 40°C (72°F) | Major discrepancy, repair immediately |
These levels provide a framework for interpreting a temperature difference, but they are not a substitute for a facility’s electrical maintenance program or qualified technical judgment. The appropriate response should be determined by qualified personnel evaluating the equipment, load, operating conditions, and facility procedures.
Reading a thermography report right now?
IR thermography and continuous thermal monitoring provide different views of equipment condition. An IR scan captures a detailed temperature snapshot during an inspection, while CTM continuously tracks temperature at installed monitoring points between inspections.
For a deeper side-by-side look at detection, visibility, safety considerations, maintenance, and system integration, read IR Thermography vs. Continuous Thermal Monitoring: What Changes When You Add CTM.
A hot connection is often a symptom rather than the underlying problem. Loose or under-torqued connections, corrosion and oxidation, overload, and phase imbalance can all contribute to abnormal heating.
Once a connection begins deteriorating, the problem can compound. Increased resistance generates additional heat, while repeated heating and cooling can contribute to further deterioration at the connection. Resistance can then increase further, allowing the hot spot to continue developing.
We break these causes down further in Top 3 Causes of Overheating in Electrical Panels and How to Stop Them.
Not every developing electrical hot spot produces an obvious external warning, but some conditions deserve attention. Discoloration or scorching, a burning or hot-plastic smell, buzzing or crackling, nuisance tripping, and brittle or melted insulation can all indicate abnormal conditions.
These signs are reasons for qualified personnel to investigate, not instructions to open energized equipment. Only qualified workers following applicable NFPA 70E electrical safety practices should open or work around energized equipment.
The absence of visible warning signs also does not establish that connections inside the enclosure are operating normally. Some developing hot spots remain hidden until equipment is inspected or monitored.
Infrared thermography is valuable because it allows qualified personnel to identify abnormal temperature patterns while equipment is operating. Its limitation is timing.
An IR scan captures equipment at one point in time, under the load and environmental conditions present during that inspection. A connection that begins deteriorating several weeks later can continue developing long before the next scheduled scan. Equipment operating below its normal load during an inspection can also make a developing condition harder to recognize.
Traditional thermography may also require access to energized equipment to establish line of sight to the components being inspected, although infrared windows can provide viewing access in some applications without opening the enclosure.
NFPA 70B includes thermography as part of an electrical maintenance program. Continuous monitoring does not make thermography unnecessary or obsolete. Instead, it provides ongoing temperature information between periodic inspections, helping maintenance teams see changes that a point-in-time scan may not capture.
The two approaches can therefore complement one another. IR thermography provides detailed thermal imaging during an inspection, while continuous thermal monitoring tracks specific critical connection points over time. For a deeper comparison, read IR Thermography vs. Continuous Thermal Monitoring: What Changes When You Add CTM.
You can also read more about the latest maintenance requirements in NFPA 70B 2026 Updates: New Requirements for Thermal Monitoring, Maintenance Programs, and More.
Continuous thermal monitoring (CTM) uses permanently installed sensors to continuously measure temperature at critical electrical connection points while equipment remains closed and operating. This allows maintenance teams to track temperature changes over time and identify abnormal ΔT trends between periodic inspections.
The GraceSense HSM 600 monitors critical connection points such as bus bars, lugs, cable terminations, and insulated conductors. It supports up to 78 monitoring points from a single cable, configurable warning and latching alarm thresholds, dew-point monitoring, cUL Listed 600VAC sensors, and integration through Modbus TCP/IP or EtherNet/IP.
By providing ongoing temperature data, the HSM 600 supports NFPA 70B and IEEE 2969 condition-based maintenance approaches and can flag developing thermal conditions so teams can investigate and plan corrective action.
Learn more about Grace Technologies' Continuous Thermal Monitoring solutions, including the GraceSense HSM 600.
Want to evaluate continuous thermal monitoring on your own equipment? Request an HSM 600 Sample and our team will follow up!
Electrical equipment generates heat under load, so some warmth can be normal. A temperature reading should be evaluated in the context of equipment ratings, ambient conditions, load, and temperature rise rather than judged by touch alone.
According to NETA Table 100.18, a connection more than 15°C (27°F) hotter than a similar component under similar load, or more than 40°C (72°F) above ambient, is classified as a major discrepancy with an immediate-repair recommendation.
Inspection frequency should be determined by the facility's electrical maintenance program and applicable NFPA 70B requirements rather than assuming one universal interval is appropriate for every panel or piece of switchgear.
Yes. Permanently installed continuous thermal monitoring sensors can monitor critical connection points while equipment covers remain closed. Infrared windows can also provide line of sight for thermography in some applications without removing the enclosure cover.
Continuous thermal monitoring uses permanently installed temperature sensors to track critical electrical connection points over time. Rather than capturing a single inspection snapshot, CTM provides ongoing temperature data that can help maintenance teams identify abnormal thermal conditions as they develop.
A hot spot does not wait for the next scheduled IR scan. Connections can deteriorate and temperature rise can develop between inspections, which is why understanding ΔT and monitoring changes over time are important parts of an electrical maintenance strategy.
The GraceSense HSM 600 adds continuous visibility at critical low-voltage connection points so maintenance teams can identify developing thermal conditions and plan corrective action.
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