Tag: heat loads

Cabinet Coolers: How to Determine Heat Loads

Published on by John BallLeave a comment

As summer continues, electrical panels will continue to overheat and cause problems within your process lines.  Freon-based coolers can be less effective in higher ambient conditions; and opening the electrical panels to have a fan blow inside creates a dangerous hazard.  The electrical industry states that for every 10oC rise above the operational temperature, the life of an electrical component is cut in half.  To reduce loss in production and premature equipment failures, it is important to keep electrical components cool.  The EXAIR Cabinet Cooler Systems are designed to do just that. 

From right to left: Small NEMA 12, Large NEMA 12, Large NEMA 4X

To find the correct type and size, we need some information about your electrical panel.  EXAIR makes it easy with the Cabinet Cooler Sizing Guide.  This sheet goes over the important details to find heat loads, proper NEMA type, and options for easy installation.  With a filled-out form, we can make sure that the correct model is recommended.  First, we have to start with the surface area of the electrical panel.  From here, we can do some heat load calculations to compare it with the proper cooling capacity. 

To properly reduce the temperature internally, we need to calculate how much heat is being generated.  Heat loads come from four main areas; internal, external, fan, and solar.  From these four, we can add them together to get the total heat load.  So, on the hottest day of the hottest month, the EXAIR Cabinet Cooler System will still keep your electronics cool.  Here are some methods to find the information needed for heat load calculations.

Internal Heat Load:  The internal load is the heat generated from inside the electrical panel.  This heat is produced from the inefficiencies of electrical devices.  There are two ways that we can figure out the internal heat load.

Step A: The simplest way is by hanging a piece of metal like a washer inside the panel for about 15 minutes.  We can get an average temperature inside.  In the sizing guide, you can mark the temperature next to “Internal temperature now”.  To calculate the heat load, we will need the external temperature at the same time you measured the piece of metal.  This temperature difference can determine the internal heat load per surface area of the panel.  See the chart below.

Step B:  if you know the electrical components inside that generate heat, a list can be made with volt/amp ratings, or watts.  This is very useful for new panels.  The major devices would be VFD (Variable Frequency Drives), power supplies, UPS, transformers, thyristors, etc.  We can calculate the inefficiency of the electrical components which will give us the internal heat load.

External Heat Load:  To keep the electronics cool on the hottest day, we will need to know the highest external temperature that the panel will see.  This can include the temperature that is near an oven.  This can be marked in the Max External Air Temperature Possible.  We can compare this to the Max Internal Air Temperature Desired.  Most electrical components are designed to operate at 95oF (35oC).   With the same chart as above, you can use the temperature difference to determine the external heat load per surface area of the panel.

Panel Fans:  To control the environment inside the electrical panels, we need to block all openings and vents.  And this will include removing panel fans if they are installed.  The Cabinet Cooler System will blow dry cold air to push out the hot humid air from the electrical panel back through the Cabinet Cooler.  Since we are removing a “poor” cooling device, we still need to add this to the heat that is being removed.  You can either give the diameter of the fan or the flow of the fan. 

Solar Heat Load:  The solar heat is only needed if the panel is located outside without cover and exposed to sunlight.  For this type of heat load, we will need to know the color of the electrical panel.  Lighter colors will not absorb as much heat as darker colors.

Because there is so much information that is critical for proper sizing, EXAIR also created a Cabinet Cooler System Calculator to give you a good recommendation to keep your electronics cool. I gave some examples above on how to find the heat loads.  Electrical shutdowns are expensive and annoying.  If you have interruptions from high internal temperatures, EXAIR Cabinet Coolers are a great solution.  They can be installed quickly and easily.  With no moving parts or costly preventative maintenance needed, they can run for decades in keeping your electronics cool.  For our U.S. and Canadian customers, you will receive an AC Sensor for free, a $65.00 value, as a promotional item from now until the end of August 2022 with qualified purchases.  How can you not give them a try?  If you have any questions about Cabinet Coolers or the Sizing Guide, you can contact an Application Engineer at EXAIR.  We will be happy to help.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Radiant Heat- Where Does It Come From

Published on by Brian FarnoLeave a comment
Even in extremely aggressive environments, EXAIR Cabinet Cooler Systems provide reliable heat protection for your sensitive electronics and controls.

The three types of heat transfer have been discussed here and there on this blog before. One of the most common heat transfer methods that I deal with on a day to day basis is radiant heat transfer. Also known as thermal radiation, the process is actually the exchange of energy by photons. The main difference separating radiant heat from convection and conduction is that radiation does not require there to be a medium to permit propagation of the heat. Any item which contains thermal energy, meaning it is above absolute zero and less than 1,000 Kelvin, will have this thermal energy. This thermal energy is radiated to other items causing a transfer of heat energy to those objects that results in an equilibrium between the items. The equilibrium does not stop the transfer of photons however.

The most common occurrence that most of us get to experience for radiant heat is heat from the Sun. As the sun shines it is emitting heat. On a hot day, generally the sun is a little closer to your geographic location and you feel hot because the sun is emitting more heat onto your surface than what is being emitted by your internal temperature, so your core temp will increase. On a cold day, when the sun is further away, while it is still shining you feel cold because the sun is not in fact transferring as much energy to the surface of your body than what you are internally generating. The same kind of radiant heat transfer can be from a campfire, open kiln, maybe even a hot steel slab coming out of a blast furnace.

The model 1126SSW 1″ Flat Stainless Steel Super Air Nozzle w/ Swivel Fitting cools a flame sensor within an industrial furnace.

Understanding where a radiant heat source is being generated can help tremendously when looking at cooling an electrical enclosure or even trying to keep a part or sensor cool. Radiant heat is one of the few times a heat shield or shade structure can help to eliminate a portion of the heat load being introduced. Other methods to combat the heat load would be determined with the application at hand. For cooling enclosures that are absorbing a solar heat load, we would look at an EXAIR Cabinet Cooler System and the factors that help to appropriately size the cooler. If this is a single component or part, we would evaluate one of the many other EXAIR Engineered Solutions to determine the best fit for the application. To do either of these, all it takes is a simple chat, email, or call to an Application Engineer.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF