You need to cool down – Heat inside an enclosure can decrease the life expectancy of controlling units such as your PLC, HMI, AC drives and other items. Excessive heat can cause nuisance faults from your electrical and electronic components: for example, overloads tripping unexpectedly. Heat will also change the expected performance of circuit breakers and fuses, which can cause whole systems to shut down unexpectedly. So, if you have any electronic equipment or other heat sensitive devices, you may want to consider these enclosure cooling tips.
What Causes All That Heat?
There are basically two sources that can cause the enclosure’s internal temperature to rise above the ratings of the control equipment.
Internal Sources The same items that can be damaged by heat may also be the source of the heat. These include items such as:
- Power supplies
- Servos
- AC Drives/inverters
- Soft starters
- Transformers
- PLC systems
- Communication products
- HMI systems
- Battery back-up systems
External Sources Other sources of heat that can cause the internal temperature of your enclosure to rise above a desired level involve the external environment. These include items such as:
- Industrial ovens
- Solar heat gain
- Foundry equipment
- Blast furnaces
How to Get the Heat Out
How do you get the heat out of your enclosure and away from those critical components? Here are there are three basic enclosure cooling tips and methods.
1. Natural Convection Cooling
If the ambient temperature outside the enclosure is cooler than the inside of the enclosure, then the heat can be dissipated into the atmosphere by radiating it through the surface of the enclosure and through the use of louvers or grilles with filters.
Example – Exhaust Grille and Filter
By placing the exhaust grille on on your enclosure heat will be able to escape though the vents. Add in an approved filter and gasket and you can maintain a NEMA 12 rating.
2. Forced Convection Cooling
If you have clean and cool ambient air outside of the enclosure, then a simple forced-air system may be adequate. A system such as a filter fan and the associated grille with the appropriate filter may be an acceptable option.
Filter Fan A filter Fan will reduced the interior temperature of an enclosure by channeling cooler filtered outside air into the enclosure, thus expelling heated internal air.
3. Closed Loop Cooling
A system that will keep the ambient air separate from the internal enclosure air is needed if the environment is harsh, there are washdown requirements, heavy dust and debris or the presence of airborne chemicals, and the ambient temperature is as high as or higher than the desired internal temperature. Air conditioners are an example of a closed loop system.
Air conditioners are designed to maintain the temperature inside an enclosure at or below a safe level for the enclosed equipment, while maintaining a closed loop environment inside the enclosure.
Originally Posted: September 2014
