In industrial facilities, electronic equipment is frequently used for motor control and most machines are PLC controlled. This use of electronic equipment has increased electrical enclosure heat loads because of the high heat dissipation characteristics of electronic equipment. At the same time, electronic equipment is susceptible to malfunction if allowed to get too hot, so it is widely accepted that electrical enclosure temperatures are kept below 100 ºF (37 ºC) to limit the possibility of unpredictable behavior or failure that could lead to a plant shut-down.
When you require enclosure cooling for your sensitive electronic equipment, dealing with the outdoor elements can complicate things slightly. Without the constant ambient environment present as in most indoor facilities or the shelter provided by the building to shield the enclosure from precipitation and other outdoor elements, the enclosure can be subjected to much more extreme conditions when placed outdoors. Here are some things to keep in mind when planning and designing your electrical enclosure cooling system to be located outdoors.
A NEMA type 4 or 4X closed loop cooling system will prevent any moisture from entering the enclosure during closed-door operation, and dirt and dust from the surroundings will also be kept out. Even so, any time the door is open for emergency repairs or routine maintenance, contaminants have an opportunity to enter the enclosure.
When constructing the enclosure, consider the prevailing wind direction, and orient the door away from the wind, so dirt and dust will not be blown directly into the enclosure. Also consider a secondary shield, such as a tarp or awning that can be erected around the enclosure when repairs will be performed. This way the enclosure will remain cleaner and drier when the door is open.
When deciding which cooling method to use for your electrical enclosure, there are a few options to consider. Among air conditioners, filtered fans, and heat exchangers, there are intrinsic differences which can keep your equipment cool and operating properly if the right cooling method is chosen. If not, the electrical components can be exposed to elevated temperatures or adverse conditions, or the cooling system will be inefficient during cooling operations.
Electrical control equipment is becoming increasingly sophisticated as designers add more features to what used to be relatively simple electro-mechanical control gear. Circuit breakers now have sophisticated electronic controls, variable speed drives and soft starters have replaced motor contactors, and PLC control has supplanted other forms of control.
Although industrial electronic components are generally robust and well designed, they are sensitive to contamination, moisture, and excessive temperature. They need to be kept cool, dry, and free of dust, debris, and corrosive chemicals. These requirements are to a certain extent in conflict because good ventilation is generally required for cooling, but protection from dirt and contamination requires a sealed enclosure.
UL stands for Underwriters Laboratories in the United States, and the initials UL represent their mark of approval. UL has laboratories in several other countries, and in Canada their mark of approval is cUL.
Underwriters Laboratories belongs to a group of nationally recognized testing laboratories; organizations that are accepted by authorities having jurisdiction (AHJs) in terms of the US National Electrical Code to certify equipment as meeting certain specifications. In simple terms, the UL label in the USA and cUL label in Canada on electrical products indicate that the products have been designed, built, and tested to be in accordance with safety standards for those respective countries by Underwriter Laboratories.