6 Common Mistakes of Enclosure Cooling Design
The design and assembly of an electrical enclosure is complicated by the need to comply with various requirements, such as those laid out in the National Electrical Code (NEC), and designers naturally focus on complying with those requirements. Strangely, the NEC makes only one passing reference to the cooling of an electrical enclosure. Perhaps it’s because of this that designers and panel assemblers so frequently underestimate the cooling requirements. Here are six common cooling mistakes that are made when assembling electrical enclosures.
1. Enclosure Cooling Is an Afterthought
Perhaps one of the most common mistakes made is to consider enclosure cooling after the design is complete and the panel is assembled. Sometimes, the need for better enclosure cooling is only discovered when the enclosure’s temperature becomes excessive, leading to the common (and problematic) practice of placing a fan outside an open enclosure door in a futile attempt to cool the cabinet. It’s far better to evaluate cooling options right at the beginning of the design process and incorporate them in the enclosure design.
2. Ignoring Ambient Temperature Range
Another common issue is that the designer is often unaware of, or ignores, the ambient air temperature in the location where the enclosure will be installed. This is a serious omission because many types of enclosure cooling methods, such as fan assisted cooling and heat exchangers, work on the principle that the enclosure will run hotter than the surrounding air temperature. In many locations, the peak ambient air temperatures are close to, if not higher than, the recommended operating temperature of many electrical components, and overheating of the enclosure is likely.
3. Overlooking Effect of Solar and Other Radiation
Another closely related factor is the effect that radiation from the sun, or from equipment such as furnaces and curing ovens, may have on the enclosure temperature. It may come as a surprise to realize that the total heat load in an enclosure placed in direct sunshine may be increased by a factor of 20 to 30 percent. Similarly, the thermal radiation from nearby equipment that is very hot may have a significant impact on the internal temperature of an enclosure by raising the the ambient air temperature.
4. Poor Electrical Enclosure Layout
There is a natural tendency to group similar items of equipment together as this facilitates maintenance and troubleshooting. However, the internal layout of an electrical enclosure should take into account the heat generated by various items of equipment, and grouping heat generating equipment, such as variable speed drives, together in such a way that the hot air from one item flows over adjacent equipment will cause local overheating.
Heat-sensitive equipment should be mounted toward the bottom of the enclosure where the air is cooler and particularly hot equipment located as close to the cool air inlet as possible.
5. Poor Air Flow
In a similar vein, poor airflow design could prevent the cool air from reaching and cooling hot equipment. Cognizance should be taken of the effect that air filters have on air flow, and any barriers that restrict air flow should be removed. These could include items such as document trays, baffles and wiring harnesses. One way to improve airflow is to provide clear channels to direct the air throughout the enclosure.
6. Heat Load Underestimated
The heat load of an enclosure is calculated by adding together the heat losses of each item inside the cabinet. This information is fairly easy to obtain from manufacturers’ data sheets. Typically, the loss for each item is a function of the power required to energize the item. However, there are several items of equipment that don’t follow this rule and it’s possible to underestimate their contribution to the total heat load. These include VFDs, rectifiers, inverters and many power supplies where the heat generated is directly related to the electrical load handled by the device and its efficiency.
Don’t Be Caught Out, Get Help from the Experts
With the high percentage of electronically controlled equipment that’s currently used in electrical enclosures, it’s essential that these enclosures operate within the thermal limits of these devices. The penalties for allowing an electrical enclosure to overheat include high device failure rate, intermittent failures and downtime.
If you are not sure how to manage the thermal design of an electrical enclosure, speak to our Support Team at Thermal Edge and they will help you design the right cooling solution for your enclosure.
