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

Intelligent Solutions for Electrical Enclosure Cooling Educational Webinar

Warmer temperatures are quickly approaching, which may seem like a welcome change for personal reasons, but in a processing line, the increased temperatures can wreak havoc on sensitive components found in an electrical control panel.

EXAIR Corporation will be hosting a FREE webinar titled “Intelligent Solutions for Electrical Enclosure Cooling” on May 23, 2018 at 2:00 PM EDT.

(click on the photo to register – it’s FREE!)

By attending this interactive session, you will learn the difference between the 3 most common NEMA ratings for electrical control panels found in an industrial setting, NEMA Type 12, 4 and 4X. We’ll provide examples of traditional, yet unreliable, methods of cooling and the concerns associated with using these types of devices.

Next we will explain how ignoring heat related issues can cause machines to shut down due to failed electrical components, resulting in lost production and increased maintenance costs, negatively affecting a company’s bottom line.

In closing, we’ll show how using an engineered, compressed air operated solution can reduce  downtime by providing a low cost, maintenance-free way to cool and purge control panels with no moving parts.

CLICK HERE TO REGISTER

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Using EXAIR Cabinet Coolers to Replace Fans

3050 with qs
Which device is causing the overheating condition?

When an electrical device mounted inside a control panel goes offline due to an overheating condition, it can be difficult to determine which component in the panel is the root cause.  There may be an intermittent heat load from a variable frequency drive that isn’t present when troubleshooting, making things appear to be OK.  Or, the overheating condition may only happen during peak operation on days with high ambient temperatures.

Fortunately, no matter the root cause, an EXAIR Cabinet Cooler can maintain temperature within the enclosure at a desired set-point, eliminating overheating conditions and lost throughput due to downtime.

IMG_3052
We investigate to determine what is housed inside of our customer’s electrical control panels.

When calculating heat load, EXAIR Application Engineers consider the components within the control panel.  We inquire with our customers regarding devices such as VFD’s, which may lead to temperature spikes, or fans, which actively remove heat (albeit that they often force dirt and debris into the enclosures they’re designed to be cooling).

IMG_3053
To accurately calculate heat load, we require the diameter of any fans installed on the enclosure.

Fans can be particularly important, because with the installation of any EXAIR Cabinet Cooler, all external fans will need to be removed, and their openings will need to be sealed (internal fans can remain in place).  So, this means we have to account for any heat the fans may already be removing from the application, even if it isn’t enough to keep the enclosure cool.

IMG_3051
Measure any fans used to bring ambient air into the enclosure.

In order to determine the amount of heat a fan is removing from an application, we consider the diameter of the fan, which corresponds to a typical air flow volume in CFM (cubic feet per minute).  We then consider that 1 BTU/hr. is the amount of heat required to raise the temperature of one pound of water by 1 degree Fahrenheit, and it is also the amount of heat needed to raise/lower the temperature of one cubic foot of air by 1 degree Fahrenheit in one minute.  This means that for every CFM the fan is moving, we are reducing the temperature of the air by 1°F .  To put it another way, we remove 1 BTU/hr. for every °F * every CFM the fan is moving.

As an example, a 3″ fan will move 22 CFM.  In an enclosure with a current temperature differential of 15 degrees Fahrenheit, this fan is removing 330 BTU/hr.

15°F * 22 CFM = 330°F*CFM

15°F

x 22 CFM X 1 Btu/hr = 330 Btu/hr

CFM °F

The fans holes should be covered up with sheet metal using rivets, caulk/sealant, duct tape or other ingenious methods you know of. But please cover and seal the cabinet as well as you can.

Using the Cabinet Cooler Sizing Guide and the experience of the EXAIR Application Engineers, we can accurately calculate heat load of an overheating electrical control panel.  When you need help with determining which Cabinet Cooler to use, contact an EXAIR Application Engineer.  We’re here to help.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE