How to Complete Thermal Management Calculations for Outdoor Electrical Enclosures



The pervasive use of electronics in control systems requires not only technical maintenance of functionality and software, but it raises the priority of temperature control inside electrical enclosures to the top of your to-do list.

You will need to develop a plan for cooling inside the enclosure to properly maintain the right operating temperature or you will increase the risk of system failures. Before you select a system to control temperature, calculate and understand the capacity your outdoor electrical enclosure requires.

Internal Heat Load

Waste heat produced by the equipment inside the enclosure can be accounted for as follows.

  • Find the waste heat by adding the published power dissipation, in watts, of all the equipment in the enclosure, or
  • Find the total amperage draw for each electrical device, multiply that number by the supply voltage and multiply the result by one minus the rated efficiency of the equipment. Add the results for each device to find the total heat load for all equipment.

Figuring Heat Transfer

Ambient temperature is simply the temperature of the air that surrounds the electrical enclosure. However, solar heat can drive temperatures up and must be considered. Heat transfers between the inside and outside of the enclosure. When the air inside is warmer than outside, the heat load transfer is negative. It is positive when the opposite is true.

Calculations should include the following:

  • Enclosure’s surface area
  • Material used to build the enclosure
  • Maximum ambient air temperature
  • Maximum temperature allowed inside the enclosure
  • Insulation used
  • Required constants

Finding the required cooling capacity for an air conditioner comes from adding the heat load and the heat transfer. Capacities for cooling systems have a range of 1,000 BTU/H to 20,000 BTU/H. Finding an accurate calculation is critical as it is all too easy to buy too much or too little cooling capacity for your application.

Selecting the Right System

The right system keeps a lid on operating costs, protects expensive equipment and helps you squeeze every drop out of your investment.

Collecting the right numbers will drive you to the right decision. Follow the steps below with the assistance of an expert in the field and you will buy only what you need.

  • Determine the NEMA rating of the enclosure
  • Calculate the heat load
  • Decide which type of system is appropriate (e.g. heat exchanger, filtered fan or air conditioner)
  • Figure cooling capacity
  • Choose a system that fits the enclosure

Like anything else involving calculations, an electronic helping hand is much appreciated. Gather your data and visit the Thermal Edge BTUH online calculator. Be prepared to enter your enclosure dimensions, ambient and desired enclosure temperatures, heat load, enclosure material, and more information about the location of your electrical enclosures. The calculator will do the figuring for you.

The experienced professionals at Thermal Edge have taken numerous customers through this process and can match the right systems to properly sized electrical enclosures, which prevents further complication that comes from multiple manufacturers. Contact our experts and get an accurate quote for your needs quickly.