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Electrical Enclosure Climate Control 101

Graham Zimmerman
Posted by Graham Zimmerman on Jul 22, 2021 9:25:00 AM

It’s summertime, and like it or not, the weather is HOT! We're lucky enough to beat the heat with air-conditioning... but what about our electrical components? Not only are they sensitive to heat and humidity, but they generate heat as they run, all within the confines of an enclosed space. Excessive heat needs to be dissipated to prevent excessive temperatures. But when is it too hot, and what's the best way to cool it down?

In this article, learn why climate control is important, how to know when your enclosure is too hot, and different methods of dissipating the heat. So let’s cool down and dive in.


cold-1293305Jump to a Section:

Why should I be concerned about enclosure climate control?
When is an enclosure too hot?
How do I determine enclosure cooling requirements?
How to cool down cabinet temperatures
   - Active cooling
   - Passive heat dissipation
Summary
Resources

 

Why should I be concerned about electrical enclosure climate control?

Climate control plays an important role to ensure the reliability and quality of communication links in your system because electrical equipment is very susceptible to high temperatures and high humidity. Overheating and condensation shortens the life expectancy of your electrical investments and causes major failures. 

It is generally accepted that industrial control panels need some form of enclosure cooling to ensure internal temperatures do not exceed safe working limits. In most instances, the panel needs to be, at the very least, fitted with cooling fans (but other solutions are often specified).

Climate control is needed because, ultimately, high cabinet temperatures decrease service life, raise the risk of component failure, and affect manufacturer warranties.


When is an electrical enclosure too hot?

landscape-2806202Electrical components are usually designed to operate under a maximum temperature of 50°C or 122°F. This might trick some into thinking they don’t need to worry about climate control but think again. Remember, your components generate heat of their own as they run, and when paired with hot ambient temperatures, enclosure temperatures can easily climb beyond that number.

In fact, if you maintain an internal cabinet temperature of 10°C (or 50°F) lower than your components’ recommended maximum temperature, you will double their service life and significantly decrease the risk of failure. That’s why it’s generally a best practice to keep your control cabinet’s internal temperature at or below 35°C (or 95°F) to ensure the maximum service life for your components.

 

How do I determine enclosure cooling requirements?

The internal temperature of an electrical enclosure is directly related to the heat load inside the enclosure, the ambient temperature, and the rate of heat removal. So let's get started by defining each of these terms.


Internal heat load


The internal heat load is the total heat of the equipment installed inside the enclosure. 
It's determined by itemizing all pieces of equipment and ascertain how much heat they generate.

For many devices, the heat load is obtained from technical documentation. For components like relays and contactors, the heat generated is approximately equal to their coil wattage. For PLCs, the heat load is derived from the consumption of its power supply. Variable frequency drives (VFD), rectifiers, and inverters are slightly more complex because they depend on the device's efficiency at its operating current.

Ambient temperature

 

This is the temperature around the enclosure or general air temperature. This is the maximum expected ambient temperature, as this will represent the worst-case scenario. If using climate data, the average maximum temperatures are never used, as these are always lower than the highest temperatures expected.


External influences


Many other influences affect control cabinet temperatures. For example, whether a control panel is exposed to the sun or heat radiation from nearby equipment must also be factored into the calculation. In addition, the extent of solar radiation, the color of the panel, its construction materials, and if it has insulation all must be equated. 


Calculating enclosure cooling requirements

Although enclosure cooling calculators are available online, these typically generate inaccurate results because all important factors are not known or taken into account. To accurately determine your enclosure cooling requirements, the best course of action is to contact a professional to audit the climate of your facility and enclosures. This allows a professional to walk through your application and measure all applicable data points to calculate your cooling requirements. Professional climate audits ensure cooling requirements are accurate to all temperatures and elements electrical components are exposed to.

Climate Control Audits & Services

 


fire-and-water-2354583How to cool down electrical enclosure temperatures

In principle, there are two ways to dissipate heat from an enclosure: active cooling and passive heat dissipation. Let's dive into each method and weigh the pros and cons of each:

 

Active cooling

Active cooling uses a medium (typically air or cooling water) to convey heat away from the enclosure. This requires additional equipment such as fan-and-filter units, cooling units, or air/water heat exchangers.


How to use the active cooling method


There are many systems available for active cooling, with the main options including:


1081PX_fri171624495_lFans & blowers

The simplest and most cost-effective solution is to use filtered fans. Filtered fans (also blowers, impellers, and direct air cooling systems) provide low to moderate heat removal when used in environments where the ambient air is moderately cool and clean.

1081PX_fri100125895_lAir-to-air heat exchangers

If your environment is cool but also hazardous or has dirty or corrosive air, using an air-to-air heat exchanger provides cooling capacity similar to filtered fans, only they use a closed-loop system to keep contamination out of the cabinet.

air conditionerEnclosure air conditioners

For locations with high ambient air temperatures, enclosure air conditioners can bring the internal temperature down below the ambient air temperature and be used in harsh locations.

1081PX_fri100125796_lAir-to-water heat exchangers

For extreme conditions where air conditioners would be subject to failure, air-to-water heat exchangers are a great solution as no moving parts are exposed to the environment.

 

Other active cooling methods include chillers and thermoelectric coolers, to name a few. If you’re considering applying an active cooling method to your cabinet, do some research, or contact climate control professionals to find the best method for your environment and application.

Active cooling pros: The most simple methods to dissipate heat. Can be easily added to a system after it's already been designed, especially if the enclosure cannot effectively utilize passive heat dissipation.

Active cooling cons: Requires the purchase of additional components and technologies to do the cooling. Special attention is required to ensure uniform heat loss.



Passive heat dissipation

With passive heat dissipation, no extra equipment is necessary because the control cabinet's panels are engineered to dissipate the heat adequately. Thus, the main benefit of this method is that no extra equipment is required, resulting in no extra energy and maintenance costs.

This method also allows for a completely closed-loop enclosure to facilitate electromagnetic compatibility (EMC) protection, protection from dust and debris, and prevent the condensation that active cooling sometimes creates.

Also, passive heat distribution creates uniform heat loss, creating a constant temperature within the enclosure. So components are less susceptible to stresses due to changes in temperature that potentially can occur with active climate control.


How to use the passive heat dissipation method


To utilize passive heat dissipation, the control cabinet needs to be carefully specified to meet the demands of the equipment inside. The material of the enclosure panels, the total surface area of the control cabinet, the ambient air temperature, and the amount of heat the electrical equipment emits ALL need to be considered.
Let’s take a deeper dive into each of these topics around passive heat dissipation:


Enclosure surface area

The enclosure's surface area is important since passive heat dissipation relies on the cabinet walls to dissipate the interior heat. Only panels exposed to open air offer heat transfer, so enclosure baying, wall mounting, or covering a panel of an enclosure reduces the surface area. In general, the larger the surface area of the enclosure, the more it can dissipate heat, so it’s prevalent to use free-standing enclosures when executing passive heat distribution.


Electrical component heat loss

The components' heat loss is the wattage it generates while in use (basically, it’s how hot it gets while running). This information is essential when utilizing passive heat dissipation, and is usually available in your components' datasheets.


Enclosure material

The material of your enclosure exterior has an important influence on passive heat dissipation. For example, spray-finished sheet steel or stainless steel enclosures are common for industrial applications and have a heat transfer coefficient of approx. k=5.5 W/(m2 x K). But the coefficient may change according to the design (for example, with double-walled or insulated enclosures for outdoor applications). The materials used in your enclosure and their heat transfer coefficient are important to calculate the heat dissipation.


Ambient air temperature & other influences

The air surrounding the control cabinet must also be taken into account when applying passive heat dissipation. A cool and climate-controlled room will allow for easier heat dissipation, while a hot environment will negatively impact your cabinet’s climate control. Therefore, it is crucial to use the maximum expected ambient temperature, representing the worst-case scenario. 


Once the above factors have been accurately calculated, the internal temperature of the electrical cabinet is determined. If the results are that your internal enclosure temperatures are too high, fear not. With a few tweaks, you may still be able to utilize passive dissipation. Alter your cabinet design to:


Increase the enclosure surface area

A simple solution to increase passive heat dissipation is to increase your cabinet’s surface area using a slightly larger enclosure. With small enclosures especially, a slight increase in surface area can significantly reduce the maximum internal enclosure temperature.


Tweak cabinet design

Installing components with particularly high heat losses (such as braking resistors) outside of the enclosure is yet another option to consider.


By increasing the size of your enclosure and repositioning the components with the highest heat loss, you might be able to utilize passive heat dissipation after all. And if all else fails, you can always implement an active cooling method to supplement your climate control. If you have trouble implementing passive heat dissipation techniques, contact our climate control experts for assistance with your enclosure design, 

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Passive heat dissipation pros:
Is a closed-loop system that requires no additional energy-consuming components. Creates uniform heat loss.

Passive heat dissipation cons: Requires complex engineering and calculations. Often needs to be considered upon the enclosure's design and is difficult to implement for pre-existing enclosures.

 

In summary

Electrical components produce heat – there’s no way around it. Luckily, there are plenty of ways to keep it under control. With careful planning and a few calculations, you can utilize passive heat dissipation to beat the heat with no extra equipment or energy costs. However, if passive cooling doesn’t keep the internal temperature of your cabinet low enough, there’s always the option to utilize active cooling methods, such as fans, heat exchangers, and air conditioners. Either way, it’s essential to recognize the importance of keeping your cabinet’s temperature under control, especially during the summer when temperatures are at their highest. Keep cool!


Additional resources

 

 

If you have a question or comment about this post, please leave it in the comments below!

 

Contact us 


Ask our Rittal product experts for assistance with climate control.

800-999-7378

CONTACT US


 

 

Topics: Electrical, Explainers

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