The Basics of Calculating Heat Load for Cooling Electrical Cabinets

Is your electrical cabinet overheating and causing expensive shut downs? As spring and summer approach, did your enclosures have seasonal overheating problems last year? Is your electrical cabinets AC Unit failing and breaking down? Then it may be time to consider EXAIR Cabinet Coolers Systems. These systems are compressed air powered cooling units designed to keep your cabinet cool in hot environments. Major benefits include no moving parts to wear out, UL listed to maintain the NEMA integrity of your enclosure (also CE compliant), they are simple and quick to install and they reliably turn on and off as needed (perfect for solving seasonal overheating).

Just one question then; how do you pick which Cabinet Cooler is best for your application? It’s time to bust out ye ole trusty calculator and crunch some numbers. Keep in mind that the following calculations use baselines of an Inlet air pressure of 100 psig (6.9 bar), compressed air temperature of 70F (22C), and a desired internal temp of 95F (35C). Changes in these values will change the outcome, but rest assured a Cabinet Cooler system will generally operate just fine with changes to these baselines.

How the EXAIR Cabinet Cooler System Works


Before we dig right into the math, keep in mind you can submit the following parameters to EXAIR and we will do the math for you. You can use our online Cabinet Cooler Sizing Guide and receive a recommendation within 24 hours.

There are two areas where we want to find the amount of heat that is being generated in the environment; this would be the internal heat and the external heat. First, calculate the square feet exposed to the air while ignoring the top. This is just a simple surface are calculation that ignores one side.

(Height x Width x 2) + (Height x Depth x 2) + (Depth x Width) = Surface Area Exposed

Next, determine the maximum temperature differential between the maximum surrounding temperature (max external temp) and the desired Internal temperature. Majority of cases the industrial standard for optimal operation of electronics will work, this value is 95F (35C).


Max External Temp – Max Internal Temp Desired = Delta T of External Temp

Now that we have the difference between how hot the outside can get and the max, we want the inside to be, we can look at the Temperature Conversion Table which is below and also provided in EXAIR’s Cabinet Cooler System catalog section for you. If your Temperature Differential falls between two values on the table simply plug the values into the interpolation formula.

Once you have the conversion factor for either Btu/hr/ft2, multiply the Surface Area Exposed by the conversion factor to get the amount of heat being generated for the max external temperature. Keep this value as it will be used later.

Surface Area Exposed x Conversion Factor = External Heat Load

Now we will be looking at the heat generated by the internal components. If you already know the entire Watts lost for the internal components simply take the total sum and multiply by the conversion factor to get the heat generated. This conversion factor will be 3.41 which converts Watts to Btu/hr. If you do not know your watts lost simply use the current external temperature and the current internal temperature to find out. Calculating the Internal Heat Load is the same process as calculating your External Heat Load just using different numbers. Don’t forget if the value for your Delta T does not fall on the Temperature conversion chart use simple Interpolation.

Current Internal Temp – Current External Temp = Delta T of Internal Temperature
Surface Area Exposed x Conversion Factor = Internal Heat Load

Having determined both the Internal Heat Load and the External Heat Load simply add them together to get your Total Heat Load. At This point if fans are present or solar loading is present add in those cooling and heating values as well. Now, with the Total Heat Load match the value to the closet cooling capacity in the NEMA rating and kit that you want. If the external temperature is between 125F to 200F you will be looking at our High Temperature models denoted by an “HT” at the start of the part number.

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

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Cabinet Cooler NEMA Ratings Explained

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Temperatures are heating up across the US, when this happens it can wreak havoc on the sensitive electronics in your facility.  If you’re a follower of the EXAIR Blog, you’ve noticed that we’ve spent a great deal of time recently discussing the Cabinet Coolers. From a description of how they work, specific applications, as well as how to determine what size you’ll need, we’ve covered quite a range of topics. Equally important, though, is the NEMA rating of the Cabinet Cooler. I’d like to take a moment to discuss the different NEMA ratings for the Cabinet Coolers that EXAIR has to offer and where each should fit.

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EXAIR’s Model 4008 Nema 12 Cabinet Cooler

NEMA 12 – The NEMA 12 rating is for enclosures that are indoor and provide a degree of protection to personnel against access to hazardous parts as well as prevent any materials from entering the enclosure such as dust, debris, or moisture from light splashing. This standard duty style of Cabinet Cooler is best served indoors on the shop floor where there aren’t any wash-down areas or excessive moisture.

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Model 4880-ETC120

NEMA 4 – A NEMA 4 rated cabinet cooler is designed for either indoor or outdoor use. It, too, provides protection to personnel against access to hazardous parts and prevents dust, dirt, or debris from entering the cabinet. In addition to providing the same levels of protection as the NEMA 12, the NEMA 4 rating also means that the equipment will be protected from water such as rain, sleet, snow, splashing water, and even hose directed water.

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Model 4880SS-316

NEMA 4X – The NEMA 4X carries the same levels of protection as the NEMA 4, but also adds an additional level of protection against corrosion. EXAIR’s NEMA 4X Cabinet Coolers are constructed of either 303 or 316 Stainless Steel.

EXAIR’s Cabinet Coolers are available from stock with cooling capacities ranging from 550 Btu/hr – 5,600 Btu/hr. With a variety of different materials and NEMA ratings, EXAIR has the right Cabinet Cooler ready to ship today to prevent your sensitive electronics from shutting down. Don’t let yourself get frustrated dealing with heat-related issues, get a maintenance-free Cabinet Cooler installed ASAP! Fill out the Cabinet Cooling Sizing Guide and an Application Engineer will be in touch with you within 24 hours with a quote for the most suitable model.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Selecting the Right Cabinet Coolers with our Sizing Guide

Selecting the proper Cabinet Cooler to solve your electrical panel overheating problems is simplified by using the Cabinet Cooler Sizing Guide and allowing EXAIR Application Engineers to calculate which Cabinet Cooler will be best. It is important to size Cabinet Coolers properly to ensure the most efficient cooler is chosen and the proper NEMA rating is chosen for your cabinet. This video illustrates how simple it is to gather the information for a long term solution to heat related problems.

Cabinet Coolers install in minutes, not hours. They protect your electronics from seasonal hot weather spikes, normally high temperature environments, or too much heat dissipation from electrical components in an enclosure. EXAIR’s selection of Cabinet Coolers include NEMA 12, 4 and 4X ratings. They normally operate with a thermostat control to turn themselves on and off as needed throughout the years and this is the most efficient way to run them. They are available from stock to solve your problem quickly and will fit nearly any environment with a variety of materials (Aluminum, 303 stainless steel or 316 stainless steel) and temperature ratings.

If you have any questions, please contact EXAIR.

Brian Bergmann
EXAIR Corporation
Ph. 1-800-903-9247 (U.S. & Canada)   1-513-671-3322
Email: brianbergmann@exair.com

 

An Explanation of NEMA 12, 4 and 4X Enclosure Ratings

EXAIR Cabinet Cooler Systems are rated to NEMA 12, 4, and 4X. But what does that actually mean?

NEMA stands for National Electrical Manufactures Association. This organization, founded in 1926, sets standards for the manufacture of safe and effective electrical products. It is an ANSI-accredited standards developer and, as such, has much credibility in the industries it serves. Many companies require or encourage the use of NEMA-rated equipment. Not having it may limit a company’s access to certain markets. In that testing, if required, is not too involved, achieving a rated unit is actually quite doable and, in the long run, worth it for safety-sake. NEMA-rated enclosures are about controlling a substance’s ability to either enter or exit an enclosure protecting electronics. Keeping you, and the electronics, safe is what this is all about. NEMA ratings are 1 through 13 with EXAIR’s cabinet cooler systems meeting NEMA 12, 4, and 4X.

So, what are NEMA 12, 4, and 4X? Simply stated:

  • NEMA 12 = resistant to dirt and oil
  • NEMA 4 = splash resistant
  • NEMA 4X = splash and corrosion resistant
    • To be rated NEMA 12, the enclosure must be built in such a way to prevent solid contaminants like air-born dust, dropping dirt, fibers, fly-off shavings, and lint from getting inside. It must also prevent dripping or slightly splashing water and oil and non-corrosive coolants from seeping, spraying, or being splashed into it.
    • NEMA 4 must be resistant to splashed or sprayed water and rain, sleet, or snow and not be damaged by ice forming on the outside. It must also prevent entry of solid contaminants like dust and dirt.
    • NEMA 4X is identical to NEMA 4 with the addition that the enclosure must be corrosion resistant.

How does this apply to EXAIR Cabinet Cooler Systems?

With our UL listed NEMA rated Cabinet Coolers, we can cool your cabinet and maintain its original enclosure integrity to protect your electronics just as needed. Our NEMA 12 cabinet cooler system is ideal for general industrial environments. Our NEMA 4 cabinet cooler system incorporates a low pressure relief valve for both the vortex tube and the cabinet air exhaust that closes and seals when the cooler is not operating to maintain the integrity of the NEMA 4 enclosure. Our NEMA 4X cabinet cooler system has the same low pressure relief valve as the NEMA 4 and is made of stainless steel, allowing for protection in corrosive and/or wash-down environments.

To further enhance their effectiveness, EXAIR offers thermostat controls to turn the units on and off as needed, which conserves compressed air. They are available with a simple thermostat (120V and 240V), an electronic temperature control or ETC thermostat (120V and 240V) which is adjustable from outside the enclosure and provides feedback of the internal temperature. Other models include a non-hazardous purge thermostat control, continuous operation, and high temperature versions that comply with NEMA 12, 4, and 4X ratings. We can meet cooling capacities (Btu/hr) at 100psig ranging from 275 to 5600. To assist in determining which system will work in your cabinet, a sizing guide is even available on our website.

Cabinet Cooler Family
EXAIR’s Cabinet Cooler Systems

If you have a cabinet that needs cooling and it is rated to NEMA 12, 4, or 4X, let us know how we can help. Chances are pretty good we can provide the cabinet cooling system you need.

John Pinchek
Application Engineer
johnpinchek@exair.com
@EXAIR_JP