It’s no fun operating with one hand tied behind your back. It’s also not smart, as it presents serious limitations. Yet, panel builders and cabinetmakers often effectively do just that because they don’t implement good thermal management practices.
Specification overkill is one culprit, which can happen when the application involves extreme environmental conditions. In the Middle East, for example, the temperature can reach 60° C (140° F).
In this case, the engineers may be tempted to focus on the external maximum temperature. That may lead to the specification of beefy active cooling for a cabinet that actually sits indoors in a location where staff will still be present. So, the actual external temperature the cabinet endures will not be anywhere near the external maximum. This temperature over-specification costs money.
Know the conditions
Understanding the true requirements of an application is the key to writing a proper spec. That requires detailed measurements, including interior spaces, as well as the temperature, humidity, and dew point.
This data may help in identifying opportunities for a significant savings in capital expenses (CAPEX) and operating expenses (OPEX). That ensures a more reliable, efficient and competitive installation.
For example, the data may show that a passive cooling solution will work, thanks to the difference between the actual temperature outside the cabinet and what the equipment inside will tolerate. The result of using fans and airflow only for cooling can be an energy savings of 70%, lowering OPEX, and the elimination of air conditioning units, lowering CAPEX.
Couldn’t you achieve the same thing by just blindly cutting out any large margin of safety? That would seem to save money, but if you don’t fully understand the requirements of an application, you’re taking the risk of thermal related failure. And that failure could be very expensive indeed, as shown in the table below.
Once you know what the conditions will be outside the cabinet, do the following to avoid over- or under-specifying:
1) Maximum, minimum and average values of temperature and humidity
Ideally there should be a temperature difference from inside to outside the cabinet of at least 5° C. As an example, say the maximum rated temperature for a component is 35ªC, a typical figure. Ambient air should then be no more than 30o C on the outside. Be sure to validate this delta T.
2) Air quality: Particle size and composition
There are many different types of particles. They can be dust, paper, cardboard, flour, milk, wine, oil, grease, cement, or even conductive ferrite.
Interior fans, electrical connections, busbars and other electrical and electronic components may be damaged or malfunction if exposed to ferrites or other particles. So, evaluate critical components carefully to determine if it’s acceptable to allow outside air into the cabinet.
A thermal calculation program, such as Schneider Electric’s ProClima, can guide you to right-size a solution for ventilating or cooling. And that’ll give you a cabinet that, as Goldilocks would say, is just right.