Heat and Control Panels: How to Protect Your VFDs, MCCs and PLCs in the Summer

In industrial environments, heat is one of the most insidious enemies of control panels and variable frequency drives (VFDs). Every summer, the same symptoms show up again: PLCs in fault, drives tripping on overheat, MCC buckets failing and, all too often, panel doors left cracked open to “let the equipment breathe.” Sometimes thermal overload relays will trip for no apparent reason if the ambient temperature is too high.

Excessive heat inside electrical enclosures is a real risk for the reliability and service life of electronic and thermal components, as well as for the safety of plant employees who may have access to control panels.

In this article, we’ll look at:

• why heat is a problem in control panels and MCCs

• how it affects VFDs, PLCs and protective devices

• best practices for ventilating, cooling and monitoring your electrical cabinets

• the role of thermography in a preventive maintenance program

1. Why Heat Is a Problem in Control Panels and Motor Control Centres (MCCs)

Inside a control panel or motor control centre, heat comes from three main sources.

1.1. Internal losses from electrical components

The following components generate heat, even under normal operation:

• variable frequency drives (VFDs/drives: IGBTs, rectifiers, internal power supplies)

• reduced-voltage soft starters

• programmable logic controllers (PLCs) and I/O modules

• DC power supplies, relays, safety modules, etc.

• any faulty contact point: contactors, disconnects, breakers

• any constant resistive load such as a capacitor bank, heating system, compressor, dust collector, dryer fan, etc.
  

Technical literature (NEMA, IEC, and VFD/PLC manufacturers’ guides) shows that, as a general rule, for certain temperature‑sensitive components (notably capacitors and some insulations), each increase of about 10 °C above the rated temperature can cut service life by roughly a factor of 2.

In practice:

A variable frequency drive that runs continuously at 50–60 °C will not age at all the same way as a VFD kept around 30–35 °C.

1.2. Plant ambient temperature

In the summer, ambient temperature rises:

• in non‑air‑conditioned electrical rooms

• in panels installed high up on mezzanines

• in already hot environments (lumber kilns, ovens, smelters, etc.)
  

2. Typical Temperatures for VFDs, PLCs and Control Panels

Exact numbers vary by manufacturer, but some general ranges are common.

2.1. Internal temperature of control panels

Many component manufacturers specify:

• a target internal temperature of ≤ 40 °C for electrical enclosures
  

• above that level, you often exceed the reference ambient used for CSA/UL certifications and must apply manufacturer derating curves, which reduces component capacity or service life
  

In a poorly ventilated panel with several VFDs side by side, it’s common in summer to see:

• an internal temperature 10 to 20 °C higher than ambient
  

A 30 °C electrical room can quickly turn into 45–50 °C inside the cabinet.

2.2. Programmable logic controllers (PLCs)

• Typical operating range: 0 °C to 55 °C

• Beyond a certain temperature, manufacturers apply derating:

  • reduced current

  • performance limitations
    

2.3. Variable frequency drives (VFDs)

• Many VFDs are rated for 40 °C with no derating

• Above that (50–60 °C), derating and “overtemp” alarms typically appear

• Installation guides are very clear about controlling the temperature inside the enclosure
  

3. Overheating Symptoms in a Control Panel or MCC

3.1. VFDs and electronic protection devices in fault

VFDs and electronic protection devices are particularly sensitive to heat. Common issues include:

• “Overtemperature” or “overheat” faults on drives

• Overload trips without any change in mechanical load

• Sporadic shutdowns of high‑power drives (conveyors, fans, pumps, dryers)
  

3.2. Unstable PLCs and communications

Overheating can cause:

• Unexpected PLC reboots

• I/O module errors

• Loss of communication on industrial networks (EtherNet/IP, Modbus TCP, etc.)
  

3.3. Visible signs inside the panel

• Discoloured terminal blocks or plastic components

• A “burnt” or overheated smell

• “Hot spots” visible with a thermal camera

• Connections loosening due to repeated expansion/contraction
  

4. Why Leaving Panel Doors Open Is a Bad Idea

In the field, we still see far too many:

• control panel doors

• wall‑mounted drive panel doors

• MCC doors left partially open to “let the equipment breathe” (!)
  

4.1. Safety risks (CNESST, CSA/UL)

This practice creates several major problems:

• Exposure to live parts (arc‑flash and electric shock hazards)

• Non‑compliance with CNESST requirements and CSA/UL certifications

• Increased employer liability in the event of an incident
  

4.2. Contamination and reliability

Open doors = more:

• dust

• humidity

• airborne contaminants

• insects and debris
  

Which means a higher risk of:

• short circuits

• contamination of circuits

• thermal instability (uncontrolled and unpredictable airflow)

Leaving panel and VFD doors cracked open is neither a technical solution nor an acceptable safety practice. You need to address the root cause: heat management.

5. Four Concrete Ways to Protect Your Control Panels from Heat

5.1. Measure the internal temperature of your enclosures

Before you start ventilating or cooling, you need to measure:

• use a thermometer or an infrared thermometer (IR gun)  

• record:
  

  • temperature at the top of the panel

  • near the VFDs

  • at different times of day (mid‑shift and end‑of‑shift)

Ideally:

• install temperature sensors and bring the data back to the PLC or SCADA

• include critical panels in an infrared thermography program

• before hot weather starts, if the control panel includes a fan, make sure the filters are cleaned, and do the same for VFD cooling fans
  

At EBI Electric, our Level 2 (Snell) certified thermography technicians can:

• detect abnormal hot spots

• distinguish a real hot spot from a simple reflection

• prioritize maintenance actions
  

5.2. Ventilate and cool panels… the right way

Ventilating a panel does not mean “open the door.” Proven solutions include:

5.2.1. Filter fans

• Air circulation between inside and outside

• Removable filters to reduce dust

• Suitable for moderately dusty environments
  

5.2.2. Air‑to‑air and air‑to‑water heat exchangers

• Air‑to‑air exchangers:
  

  • closed system; transfers internal heat to ambient air through a heat exchanger

  • useful when ambient air is cooler but dusty
    

• Air‑to‑water exchangers:
  

  • very effective if a plant cooling‑water network already exists

  • used in some heavy industries
    

5.2.3. Enclosure air conditioners

In environments where:

• thermal load is high (multiple VFDs, PLCs, power supplies)

• ambient temperature is high or fluctuates significantly
  

Enclosure air conditioners are often the most reliable solution:

• stable, controlled internal temperature

• independent of ambient variations

• dust protection (closed circuit)
  

As a certified Rittal integrator, EBI Electric uses:

• side‑mount A/C units

• roof‑mount A/C units

• air‑to‑air and air‑to‑water heat exchangers

taking into account:

• total power dissipation of panel components

• maximum ambient temperature

• required degree of protection (IP, NEMA, dust, humidity)
  

5.3. Protecting and “tropicalizing” VFDs and electronics

In environments that are:

• hot

• humid

• corrosive (sawmills, lumber kilns, smelters)
  

Conformal coating (“tropicalization”) of electronic boards is recommended:

• protection against condensation

• protection against dust and corrosive vapours

• better performance under combined heat + humidity
  

Two key moments:

• At purchase: choose VFDs and modules with a conformal‑coating option

• During maintenance/repair: when sending equipment to a qualified repair shop, take the opportunity to apply or renew conformal coating, where compatible with the product
  

Be cautious: there must be a proper balance in the conformal‑coating process. If the varnish used on components is poorly chosen, poorly applied or too thick, it can prevent the electronic parts from dissipating heat properly and “breathing” enough. This procedure should be entrusted to repair shops that are qualified in conformal coating.

5.4. Integrate infrared thermography into your preventive maintenance

A Level 2 electrical thermography program allows you to:

• identify:
  

  • overheating connections (loose terminations)

  • hot busbars

  • breakers, fuses, overload relays with abnormal dissipation

  • VFDs or power supplies that are running unusually hot
    

• distinguish:
  

  • a real problem (repeated hot spot)

  • from an artefact (reflection, material effect)
    

• prioritize:
  

  • urgent interventions

  • actions to schedule during the next shutdown
    

Integrated into a predictive maintenance program, thermography:

• reduces heat‑related failures

• lowers the risk of fire in electrical enclosures

• extends the life of key components (VFDs, PLCs, terminal blocks, cables)
  

6. Control Panel Maintenance Best Practices Before Summer

Every time you open a control panel or MCC (safely, with proper lockout/tagout and PPE), take the opportunity to:

• check wire labelling and terminal block condition

• re‑torque critical connections (after de‑energizing and performing proper tests)

• inspect cabinet cleanliness (dust, debris, condensation)

  
  

• check the condition and operation of:

  • panel fans  

  • VFD cooling fans
    

• verify that:

  • doors close properly  

  • door gaskets are intact

  • cable glands and entries are properly sealed
    

7. In Summary: Get Ahead of Heat Before It Damages Your VFDs and Panels

For millwrights, I&C technicians, electricians and electrical engineers, hot weather is a high‑risk period for control panels and MCCs. VFDs, PLCs and electronic protection devices do not handle excessive temperatures well, and every unplanned shutdown translates into lost production.

By combining:

1.  Systematic measurement of internal enclosure temperatures

2.  Proper ventilation and cooling (filtered fans, heat exchangers, enclosure A/C units)

3.  Protection of VFDs and electronics (conformal coating, properly selected products)

4.  Level 2 infrared thermography as part of your maintenance strategy

Thorough inspection and maintenance of panels before and during summer you can dramatically reduce heat‑related failures and extend the life of your critical components.

Finally, at the control panel design stage, if the variable frequency drives in your application are sized a bit too “tight” for the work they’ll be doing, they are likely to run even hotter during the summer. Depending on your applications, in some cases it may be wise to oversize the VFD slightly and also provide a bit more spacing between panel components to help them dissipate heat more easily.

If you’d like to:

• assess the thermal situation of your control panels or MCCs

• integrate appropriate ventilation and cooling solutions

• or plan a thermographic inspection before hot weather arrives

the EBI Electric team can support you, from thermography right through to integrating Rittal cooling solutions, and can assist you in modernizing your control panels and motor control centres.