Saving energy with NEMA enclosures

A member of the Control Engineering Automation & Control Facebook site highlights energy considerations related to NEMA cabinets.

02/17/2009


Editor’s note: Discussions on Control Engineering’ s Automation & Control ” group on Facebook, recently led to a posting about energy saving considerations related to NEMA enclosures. The posting, by David Marin from Noren Products , appears below, along with a link to additional tips.
Over the past few decades, the use of electronics for automation, process controls, drives, and PLCs have become more commonly installed in NEMA enclosures (cabinets used to protect electronic devices from the harsh environments encountered in many industries, both indoor and outdoors). Though most electronics can handle temperatures between 40 and 50 degrees C, it’s always a good idea to check with the manufacturer regarding the heat load specifications of the device being used; this will help in making the correct thermal decision for your applications.
Enclosure tips: Correct size, fan filter, cooling
Following is a rundown of the most important issues to consider when investigating the thermal management capabilities of electronic enclosures.

  • Purchasing a cabinet large enough so that natural convection can be used to remove the waste heat through the cabinet. Though this is sometimes a preferred cooling method, be sure to investigate that this approach will not actually cost more money than installing cooling capabilities, due to the cost of the larger metal cabinet.

  • Pay close attention to the fan and filter. This option is the most economical of all, but is not preferred in dirty environments. The extra maintenance needed to clean the electronics within the cabinet defeats the cost savings and puts expensive electronics at risk.

  • Check out the cabinet’s thermoelectric device. A cabinet’s solid state air conditioner can provide cooling, but uses one watt of energy to remove one watt of heat. These devices are typically used in small cabinets and are not very efficient.

  • Investigate the air compressor coolers, which use plant air to create a “cyclone” effect that cools the inside of the cabinet. The cost of plant air should be considered, as well as whether or not the air used is clean. Unclean air can produce an oil mist inside the cabinet.

  • Consider the panel air conditioner. When electronics first came into the plant, air conditioners were used because of the thermal thresholds of the electronics required that the temperatures be below ambient conditions. Now, however, the components are made to withstand more heat. Air conditioner units cost more to install and maintain and use more energy than most other options. Thermostats are a common option to regulate the operation of air conditioners in certain cabinet conditions.

  • Study the heat exchangers or cabinet coolers. These devices are being used more and more because of energy savings and low maintenance. Most heat exchangers are designed to be sealed from dust in the air and some can protect against moisture and corrosion. They are generally easy to install and very reliable. They also can be used with thermostats. Air to water heat exchangers can be used for high ambient applications were water is available.

  • For all outdoor applications, sun load should be a consideration and most enclosure companies or thermal management companies can help with this calculation. Generally it’s a good idea to consider a sun shield.

Also read:
- Enclosures: Improve NEMA designs, enclose wireless equipment, keep cabinets cool .
- Proud of your control panel design? Share your knowledge .

– Edited by David Greenfield , editorial director

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