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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Calculating Heat Loads to Cool Electronic Cabinets

With the hot summer months upon us, elevated temperatures can cause shutdowns and interference with electrical systems.  For every 10 deg. C rise above the operational temperature, the life of an electrical component is cut in half.  With Freon-based coolers, higher ambient conditions make them less effective; and opening the electrical panel to have a fan blow inside creates a dangerous hazard as well as blowing hot, humid, dirty air inside the panel.  To reduce loss in production and premature equipment failures, it is important to keep the electrical mechanisms cool.  The EXAIR Cabinet Cooler Systems are designed to do just that.

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. The EXAIR Cabinet Coolers range from 275 BTU/hr (69 Kcal/hr) to 5,600 BTU/hr (1,411 Kcal/hr) in cooling capacities.  And with the filled-out form, we can make sure that the correct model is recommended.  In this blog, I will cover a section of the sizing guide, the heat loads.

To properly cool, we need to calculate how much heat is being generated.  Heat loads come from three main areas; internal, external and solar.  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 the electrical devices.  There are three ways that we can figure 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.  The best place for the washer will be toward the top half of the panel, as heat rises.  In the sizing guide, you can mark the temperature next to “Internal temperature now”.

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.

Step C:  If you know the amount of power going into the panel, and the amount of power leaving the panel, the difference will tell us the amount of power that remains for the electrical components.  We can take a 5% average as the heat loss.

External Heat Load:  The external heat load is attributed to the environment surrounding the electrical panels.  This is a standard temperature reading in oF or oC.  Only with Step A above, we will need to know the external temperature at the time that you measured the internal heat measurement.  This needs to be placed in “External Temperature Now”.  The difference to the internal temperature will give us the heat load per square feet (square meter).  Reference chart below.  We will also need to know the highest external temperature that the panel will see.  So, during the hottest day of the hottest month, the EXAIR Cabinet Cooler will still be able to keep your electronics cool and operational.

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, the Cabinet Cooler Sizing Guide is the best tool to use to facilitate the calculations.  I gave examples above to find different ways to get the proper information.  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 $58.00 value, as a promotional item from now until the end of August 2020 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

Cabinet Coolers Material Selection Focus: 316 Stainless Steel

Industrial environments call for equipment to be constructed of many different materials in order to stand the test of time and to meet standards set by governing agencies. Within certain environments, 316 stainless steel rules the world and there is due cause for it. In given areas, there may be chemical incompatibilities, temperature limits, or even material incompatibilities between parts within a process and the process itself.  This is why the EXAIR Cabinet Cooler Systems are available in 316 stainless steel.

The NEMA Type 4X Cabinet Cooler Systems are standard in 303 stainless steel while 316 stainless steel is also available from stock and can meet or exceed the standards set forth by NEMA Type 4X environments to stand the test of time whether it be chemical/caustic washdowns that generate the need, product material compatibility, or due to being outside.  These systems are offered in both thermostatically controlled with choice of 120 VAC, 230 VAC, or 24 VDC solenoid valve or continuous operation and can all ship same-day on orders received by 3 PM ET for domestic orders.

We also offer Hazardous Location NEMA Type 4X Cabinet Cooler Systems in both 303 and 316 stainless steel to cover even more stringent classified areas that demand UL Classified certifications.   These meet certifications for Class I Div 1, Groups A, B, C and D, Class II Div 1, Groups E, F and G, as well as all Class III environments.  These systems are also offered in the same thermostat control voltages as well as a continuous operation.

The point is, if you have an overheating control panel or electrical panel, we will have a solution that can keep your production running, all you have to do is contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

 

Cooling Electronics Down With Cabinet Coolers

As the summer days have reached maximum temperatures, I find myself busting out my kayak and heading down to the wild whitewater rivers for a weekend full of adventure in the cool water. I personally am not a fan of the heat and as most people enjoy the water and swimming, I partake in the high adventure sport of whitewater kayaking. I’ve been around the sport of whitewater most of my life and have kayaked some of the hardest rivers east of the Mississippi including the well-known rivers of the Upper Gauley, the New River, and the Tallulah.

When the temperature rises and I start to overheat and kayaking is the best way that I enjoy to cool off and enjoy the weekend; splashing around in the wild waves. With plenty of summer heat ahead of us it’s a perfect chance for all to get outside and jump in a lake, swimming pool, or even a river to cool down and take a chance to enjoy a little fun.

Baby Falls on the Tellico River

But what about your electrical cabinets; they deserve to stay nice and cool on the inside as well. All electrical components are not 100% efficient meaning that when an electrical current is flowing through them a certain amount of heat is generated. This phenomenon is commonly referred to as heat loss and VFD’s and other drives are typical offenders. Heat loss is not the only thing that can attribute to electrical cabinets overheating, sun light is another big factor for outside electrical cabinets. Based on the color of a cabinet sitting out in the sun a specific percentage of heat is absorbed into the cabinet; black absorbs the most heat and white absorbs the least. In most cases solar heat can be negated by installing a cover over top of the cabinet to provide shade.

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

At EXAIR we have designed a cost-effective way to cool down these overheated cabinets during these summer months. EXAIR’s Cabinet Coolers are designed to provide cooling using just a source of compressed air; they utilize our vortex tube to provide a constant source of cold air as long as they are connected to a source of compressed air. Our Cabinet Coolers have also been designed to be used in a large variety of environments ranging from standard production to Classified environments.

NEMA 4 Dual Cabinet Cooler System with ETC

EXAIR also can provide our Electronic Thermostat Control system or ETC for short which can give a user much better control over the temperature inside the cabinet as well as visual feedback of the internal temperature. The ETC allows for easy and constant changing of what internal temperature is desired. The ETC will also provide live temperature readings on the internal temperature of the cabinet.

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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Follow me on Twitter
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