Thermal Management – STEGO, Inc.

STEGO USA is based in Atlanta, Georgia, smack in the middle of the Southeastern U.S. It’s March, and spring is right around the corner. Many employees have been using individual office heaters for the winter season to stay comfortable. Facilities managers have strict regulations on the types of heaters that may be used, as there is a risk of fire or high power draw inside an office building.

We have personally experienced this hazard in our own office building. One of our office employees is cold-natured and uses two space heaters to keep her office warm. Recently, on a very cold day, between the draw of extra space heaters and our office thermostat, it tripped our local circuit, cutting power to the heaters, the computer monitors, lamps, printers, etc. for our section of the office. Until someone from maintenance could reset the panel, we could not work.

In electronics enclosures, designers include heaters to avoid temperature drops inside the cabinet, preventing the formation of condensation.

Condensation, if not controlled, can lead to safety or reliability issues for the electronics contained within.

Reliability is sometimes better stated as downtime avoidance – kind of like our office example above. As users, we expect uptime – and so do your customers.

There are many choices in cabinet heater technologies, but the two most prevalent are Resistive and PTC. Both accomplish the same task but in different ways.

Resistive heating is the process of converting electricity into heat energy. Fixed wattage heaters are typically manufactured with resistive wires or etched circuits. A toaster is a great example of resistive heating where the wire in a fixed wattage heater must reach a very high temperature to dissipate the desired temperature across the area to be heated. A thermostat or temperature sensor is used to keep the heater from overheating. This single point sensing method remains one of the crucial problems with fixed wattage heaters.

Any sensor or circuit failure can lead the heater to reach dangerously high temperatures, thus becoming hazardous to the user. Furthermore, the heater will continue to draw power if the temperature sensor does not detect the malfunction.

Other potential failure modes associated with fixed wattage heating include hot spots, broken conductors, and overheating.

PTC

STEGOs Touch safe PTC heater — The CSF 060 is a touch-safe PTC heater for use in enclosures.

Positive Temperature Coefficient (PTC) heaters are self-regulating heaters that run open-loop without any external diagnostic controls. While traditional fixed-resistance heaters employ wires and coils to generate heat, PTC heaters use conductive inks printed on thin, flexible polymer-based substrates.

Scoring high on reliability and efficiency, PTC heaters are ideal for products that require safer, faster, and more uniform heating.

The material properties allow the PTC heater to act as its own sensor, eliminating the need for any external feedback controls. As a result, the heater inherently removes the risk of overheating.

Electronics cabinet designers have multiple competing priorities – uptime, cost efficiency, risk mitigation, and others. By selecting PTC heaters, you’re picking the right solution for you and your customers, reducing your headaches in the short term, and in the long term.

Designing complex electronics that perform perfectly outdoors is, well, complex. At STEGO, we believe that protecting those complex projects from extreme climates should be the simplest part of your design. That’s why we use German engineering to create the highest quality thermal management components to protect your designs from anything Mother Nature throws at it. We’ve been pioneering Thermal Management for over 40 years now. With STEGO parts installed, you can rest easy that your complex design is reliably protected for the long haul.

Computers in College Computer Lab I talked with my children the other day about how quickly the world of information access is changing. They were fascinated to learn about how I went to college in the 1990s (in my head at least, it wasn’t that long ago!), and I had to (gasp!) walk all the way to the computer lab on campus to type my papers, as hardly anyone had a computer of their own. Getting that critical paper completed on time meant pre-planning to make sure it wasn’t too cold or rainy to walk to the lab and that you wouldn’t get to the lab at the same time as the rest of your colleagues. I can distinctly remember forcing myself to learn the new Mac OS because the Computer Science majors occupied all the Windows PCs!

Telecom Network Reliability

Now here we are today, and we don’t usually have to worry about pre-planning to avoid weather or computer lab availability…but watch out if our YouTube cat video doesn’t download and play immediately.

The expectation in today’s world is instant gratification, with no downtime or download delays.

The traditional standard for telecom network reliability, measured at the service level, is six-nines or 99.9999%, which translates to an average of 32 seconds of downtime per year per service.

Electric Vehicle (EV) Charging Network Reliability

It is also interesting to watch the burgeoning EV market. New buyers are entering the marketplace, and some of these consumers have ‘range anxiety’ – the fear of not having enough charge to reach their desired destination. EV Charging companies are mitigating this with more extended range battery packs and a growing number of well-placed EV charging stations.

The expectation of EV Charging uptime is not yet to the “six 9’s” of telecom, but they are not far behind. The CEO of EV Go touts 98% uptime on their fast-charging network. OEM’s in this space are discovering they can tout reliability (uptime) as a market share growth strategy.

Uptime Risks

Because Telecom and EV Charging cabinets both involve outdoor exposure, precautions must be taken to ensure hardened designs. One failure mode that isn’t as well documented is induced condensation.

Electronics enclosure designers must minimize the chance for induced condensation, as this could lead to electronics failure. The formation of condensation is one of the biggest dangers for electrical enclosures. Condensation is caused by hot, humid air coming in contact with a surface colder than the ambient air dew point. When the humidity is high, it does not take a significant temperature change to cause condensation to form inside the cabinet.

If condensation occurs, potential failure modes include:

Short circuits
Corrosion
Premature breakdown
Contamination by mold and other organisms
Water drainage from enclosures
Risk of electrical shock to employees

Uptime Risk Mitigation

There are different tools to minimize condensation inside electronics enclosures. The most effective tool is a comprehensive design that considers both temperature and condensation. DC Heaters like those offered by STEGO are an excellent fit to minimize condensation buildup. STEGO products include PTC, touch-safe PTC, and flat heaters, as well as an explosion-proof option.

By thinking ahead and planning for condensation, designers can maximize uptime for their clients, leading to enhanced market share and customer satisfaction. You’ll be able to use your mobile phone to see more cat videos and get fewer panicked calls to diagnose what went wrong in the field!

Are you a wizard? If you watch pro football, you’re probably familiar with Tony Romo. He’s the former Dallas Cowboys quarterback who has seamlessly transitioned into broadcasting. Tony has an uncanny gift for predicting plays before the snap, so much so that people joke that he must be a wizard. Check out this clip https://tinyurl.com/4rr5khbe from the Patriot’s win over the Chiefs in an AFC Championship Game, and prepare to be amazed.

Much of Tony’s gift comes from his experience under center, coupled with an ambiguous term called “Football I.Q.”

When it comes to designing cabinet enclosures, especially when doing thermodynamic calculations – there’s a bit of wizardry. Some of what is considered best practices are things you learn in university. But the lion’s share of knowledge comes from experience. Like in most industries, electronics design is going through an upheaval in the workforce as veterans of the trade retire, while young engineers enter the workforce to pick up and carry the workload.

Today we’re going to talk about cabinet thermostat heaters – the “do’s and don’ts” we’ve collected over our years of experience from talking directly with customers around the world. Allow us to impart some of our wizardry:

You may ask yourself – did someone violate the last “DO NOT” instructions and mount their heater near a flammable surface? The answer, believe it or not, is YES. No one was injured, but on a recent field visit, we found a thermostat heater mounted on a wooden 1×4. Yikes!

While there will still be those that cut corners, touch-safe heaters from STEGO are manufactured with safety in mind. The design of the heater utilizes natural convection, which results in a circulating current of warm air. The surface temperatures on the accessible side surfaces of the housing are minimized because of the heater design. This STEGO heater is suitable for permanent operation. If you follow the operating instructions, you can install a touch-safe heater and know you’ve done all you can to protect anyone working near the cabinet internals.

We’re not wizards, but hopefully, this information helps you keep your design safe from spells and incantations!

In the ever-increasing demand for power and data, mission-critical telecom and electric vehicle (EV) charging stations share one common need: absolute reliability. Both telecom and EV charger manufacturers want a solution that they can rely on to perform flawlessly.

The rapid growth of EV’s such as Tesla, Lucid, VW, and Renault-Nissan is expanding the need for EV charging stations, and drivers expect “five 9’s” reliability when they pull up for a battery charge. In a recent Spring 2021 Financial Times article, the CEO of EV GO, Cathy Zoi, was quoted as saying, “… we have a sophisticated network of fast chargers across the country that we keep running at 98% uptime. We are more than just a commodity supplier, operating chargers that are reliable….”

For EV Charging companies and for the EV owner, it’s simply unacceptable for a charging station to be out-of-order, especially as new EV drivers grapple with potential range anxiety.

Telecom

As the insatiable need for data increases, particularly with the advent of 5G networks- and 6G right behind it, telecom operators need to know their towers work with…wait for it…five 9’s reliability (sounds familiar, right?).

This brings us to another commonality; the risk presented by environmental exposure. We’re not talking about force majeure here (i.e., a hurricane, a 100-year flood, or record high temperatures; those are one-offs) – we’re talking about relatively predictable temperature and moisture exposure. In a previous blog on this site and numerous technical articles, we’ve documented STEGO’s thermal management expertise in combating temperature and moisture. Today’s blog post will focus on the thermal side of the equation (with a nod or two to moisture and condensation).

The goal is to select a solution that will avoid temperature drops in your equipment, preventing the formation of condensation. STEGO offers a wide range of technologies, including PTC heaters, convection heaters, and panel heaters/enclosure heaters. Each offers a unique feature set designed to solve your enclosure heating needs. In addition, we have built-in solutions for varying enclosure profiles, different voltages, mounting technologies, and the ability to interface with sister assemblies such as thermostats.

If your current design philosophy doesn’t include comprehensive thermal management, you may have a ticking time bomb. Don’t risk your user’s satisfaction, your technician’s safety, or your company’s time trying to figure out that intermittent failure that keeps popping up on the network. It can be confusing, but here at STEGO, we’re here to help; just reach out to one of our experts.

As we get ready for all things Fall & Winter, it’s time to start thinking about things like football, Halloween decorations, and cooler temperatures. Not everyone likes these cooler seasons as much as I do (my wife, for example, would prefer only two seasons: Hot and Hotter), but whether you like it or not, Old Man Winter comes every year.

When it comes to your electronics enclosure, we encourage our clients to think holistically. You need to consider both temperature extremes and condensation risks. Today’s post will focus on cold temperature exposure, but with a wary eye on the risks associated with condensation.

Cold Weather Packages For Your Outdoor Enclosure

If you’ve forgotten more than you remember about thermodynamics, that’s ok, because we’re here to help. Beyond simple online heat dissipation calculation tools, there are other questions to consider so that you have a complete solution set for your unique application.

Can one wattage/voltage design work in all geographical locations?

A solution that works only on the test bench but doesn’t consider regional power connections could be problematic. We suggest customized solutions that are specific to your location.

Will AC power always be available?

You may need to consider backup / DC power to maximize uptime.

Have you considered Touch-Safe / maintenance crew safety?

“Even minimal-voltage installers can still be subjected to alarming jolts, especially if they are working in a hazardous environment such as when they are ungrounded or standing on a wet spot…” says the NECA Executive Director of Standards and Safety.

Does my design need two heaters?

Sometimes one heater is not enough to keep electronics safe in frigid temperatures.

The answers to these questions will determine how best to design a solution that can likely handle anything Mother Nature throws your way. Depending on how you answer these queries will help us guide you down the right hardware path, a path that might lead to a solution involving a:

Our goal at STEGO is to make sure your design avoids potential blind spots. We offer a comprehensive review that takes into consideration both temperature and condensation. We want to minimize the risk of failure, allowing for maximized uptime. Contact us today for a consultation, so you know you’ve selected the right thermal management solution, despite temperature and condensation exposure.

My Dad is the smartest man I know. He majored in Physics and graduated near the top of his class, in an era before laptops, graphing calculators, and the Internet. Even more amazing to me,

Backgrounds and textures: group of old slide rules, or slipsticks, retro science abstract

he did all his calculations using a slide rule (pictured left). I now have my Dad’s slide rule proudly on display in my office; it reminds me of my Dad and all the lessons he taught me. Today we rely on computers to do the heavy lifting when calculating heat transfer rates and other thermodynamic data. Thank goodness we don’t have to remember how to use a slide rule!

Here’s the key, though – whether using a slide rule or your iPad, there are fundamental principles that still must be respected, no matter how you get to the answer. In other words: how you get to the solution doesn’t matter. All that matters is that you make the right engineering decision. That choice needs to consider the system requirements AND the total system cost.

In terms of electronics thermal management, we need to challenge certain assumptions to design the most cost-effective solution that will protect your device from temperature extremes.

Changing the paradigm: Active vs. Passive Enclosure Cooling

Air conditioning is considered active cooling. Like in your home in the heat of summer, you simply set the temperature and the unit maintains it, just like you programmed. Simple right? Not so fast!

As humans, we like a specific temperature to function at our peak. The same applies to the electronics inside your enclosure. However, although air conditioning may work fine in your design, it might be overkill. Consider these factors:

Power requirements:

An air conditioner will require the most power compared to other (e.g., passive) technologies.

Cost:

Active cooling solutions cost the most initially and on an ongoing / maintenance basis.

True system requirements:

Many times, your electronics need only to be slightly cooled, not requiring a very tight window of control or not requiring a temperature significantly below ambient.

Condensation risk:

Air conditioning removes humidity from the air, but that condensate has to go somewhere. So you’ll have to engineer some way to handle this thermal “waste stream.”

A filter fan may be a better choice. Filter fans are used to provide cooling via forced air circulation. The interior temperature of an enclosure can be reduced by channeling cooler, filtered outside air into the enclosure, and pushing hot air out of the enclosure. The resulting airflow prevents the formation of localized hot pockets and protects electronic components from overheating.

A filter fan can protect your enclosure from high-temperature exposure with:

Fewer power requirements.
Less cost to install and maintain.
Less mess, with no troublesome condensate to be managed.

Our takeaway: don’t always assume you need to design an air conditioner for your electronics enclosure.

We can help you select the right thermal management solution. Contact us today for a consultation.

We get it. We’re in the thermal management business, and we’ve heard the jokes about fans versus air conditioners. Usually, it’s someone asking about, for example, getting in a vehicle on a hot Summer day in the South and instead of turning on the air conditioner… why not just crank up the fan instead (cue laugh track)? When it comes to controlling the environment inside an enclosure, it’s a similar question:

Aren’t you just replacing hot air with more hot air?

Geek humor! But seriously, we do get this question from enclosure designers, who want to know why they don’t just go ahead and design in an air conditioner. In this case, the temperature desired for a human body is much different than what is necessary to maintain the integrity of electrical and electronic components. So essentially, an A/C is overkill for most NEMA enclosures needing environmental control.

STEGO offers a wide variety of Filter Fans that provide a net cooling effect via forced air circulation. The interior temperature of an enclosure can be reduced by channeling cooler, filtered outside air into the enclosure, thus expelling hot inside air. The resulting airflow prevents the formation of localized hot pockets and protects electronic components from overheating.

So, no, our technology doesn’t just move hot air. Instead, it modulates the air inside the enclosure to a cooler state. This, in turn, enhances the longevity of the components inside and the working life of the overall enclosure. Furthermore, with the addition of new air-flap technology on the air outlet side, we have achieved an unparalleled high degree of airflow.

What’s the difference between FPI or the FPO system (FPI = “in”, FPO = “out”)?

This is another question our tech support teams get asked regularly.

There are two distinct filter fan options. The FPI system is the more commonly utilized installation system. A filter fan located in the lower part of the enclosure draws cleaner, cooler air into the enclosure (airflow direction “In”). This system consists of a filter fan and an exhaust filter.

With the newer FPO system, the filter fan will be located in the upper area of the enclosure to draw warmer air out of the enclosure (airflow direction “Out”). The FPO system consists of an intake filter and exhaust filter fan.

For a video explanation of how this all works, check out this link: STEGO Filter Fan Plus Animation

The answer to the title question is simple economics: it’s just not feasible to power, control, and manage an air conditioning unit inside most NEMA enclosures. Also, it’s overkill!

For more questions about thermal management, reach out to one of our experts.

Although you may not have grown up in the ’80s, you’ve likely heard of the 80’s rock band, Def Leppard. One of my favorite hit singles from the same-titled album is “Hysteria.” Take a trip down memory lane and give it a listen (or, if you’re * ahem * much younger, just give it a try anyway, and don’t rub it in on us older folks!)

Hysteresis… isn’t that a Def Leppard Song?

This isn’t about big hair bands and one-armed (but still awesome) drummers. It’s about hysteresis. An understanding of application-specific hysteresis is one of the design features of the STEGO Compact Thumbwheel Thermostat.

To get a better understanding of this feature, let’s start with a definition. The dictionary defines hysteresis as retardation of an effect when the forces acting upon a body are changed.

Hmm… that is still a bit confusing.

Let’s look at our homes since the thermostat in your house’s HVAC offers a good example.

Say you like your home temperature at 72 degrees. If the A/C tries to keep that nice, even 72 degrees while it’s 98 degrees outside, the system will struggle to keep up and will constantly turn on and off.

With a hysteresis thermostat, you can set your temperature to 72 degrees and be better able to maintain it. Why? The temperature will go up to 74 degrees before cooling it down to 71 degrees, allowing the HVAC system to relax. This saves on wear and tear and fosters energy efficiency.

Thus, you can stay cool while you air guitar to your satellite radio’s “Big 80’s on 8”.

Now – back to electronics enclosure design, where we have a similar goal. You need to maintain a temperature setting, but a very tight temperature window could overtax your system, potentially leading to poor energy efficiency. At STEGO, we know thermal management, and we’ve built in ‘smart hysteresis’ into our thermostat design. Sometimes a picture is a better way to visualize a concept, so see this chart below for an example:

The image above depicts the expected closed/open contact state for a 20℃ setpoint across an operating temperature range. Note the expected results given the hysteresis 7K with a tolerance of 4K. The tolerance can be confusing to interpret, so feel free to give us a call to help further explain.

There are other key features of this product, including anti-frost assurance and high switching capacity. For more information, see the full datasheet here (https://www.stego-group.com/fileadmin/Languages/English_UK/STO011_STS011_EN.pdf).

The compact thumbwheel thermostat is but one example of the many tools we offer at STEGO. The continual battle against heat and humidity to keep your control enclosure running smoothly is annoying and costly. Our German-engineered thermal management solutions will do that fighting for you, so you can spend your time designing instead of monitoring and fixing (doing damage control).