Overlooked Enclosure/Cabinet Internal Climate Issues

Items to consider in Climate Control

I often get involved in evaluating temperature problems on installed enclosures/cabinets. Frequently after "turn over" to the client, some cabinets start to develop hot spots.

One item repeatedly overlooked is properly evaluating specifications for inside and outside plant Cabinets and Enclosures operating temperatures. We know that the components installed are generating heat and regulating the temperature is necessary to keep condensation down, as well as operational safety and equipment life, inside the enclosure. Furthermore controlling temperatures inside, calls for implementing some form of enclosure cooling or heating. 

The physical size of the enclosure is the primary factor in determining its ability to dissipate heat. The larger the surface area of the enclosure, the lower the temperature rise due to the heat generated within it. The temperature in Sealed Enclosures is difference between the air inside, a non-ventilated and non-cooled enclosure and the ambient air outside the enclosure. The result is a calculation of the heat generated within the enclosure.

Installed Systems

Heat is much easier to evaluate and calculate on the panel shop floor, but extremely difficult if installation teams are not aware of some common mistakes that can be prevented.

Positioning of devices and equipment:

Sounds simple, such as in the case of a Drive System, providing the “best fit” cooling solution starts with keeping some distance from heat producing devices. Cooling components with bottom-up air flow (in the correct air flow direction) is the first item to consider. Furthermore, keeping clearances for ventilation allows the air to flow around the device. This is where incorrect distance between components will cause an issue. 

Recommendation: Keep 100 MM spacing

This may sound easy, but if the panel layout does not take this into account, then inside climate control can only be achieved by moving to larger mounting panel.

Recommendation: Look to vendors like Rittal that have modular enclosures that have larger mounting panels in the same physical space.

Recommendation: Do not cover the air vents

Without proper knowldege installers may be placing components and cables in this area. A cable duct on a mounting plate is not a clearance! You will find that air duct systems need to be mounted so the air flow is not blocked.

Heat Dissipation in Sealed Enclosures

As Heat Dissipation in Sealed Electrical Enclosures accumulates it shortens the life of the inside components, but may also be a safety issue during a catastrophic failure. Engineers can consider different types of Enclosure Materials. When Higher temperature rise unfinished aluminum and unfinished stainless steel enclosures due to their material’s have less efficient radiant heat transfer. Non-metallic enclosures have similar heat transfer characteristics to painted metallic enclosures. Also, unless you have a single component in the enclosure some type of climate control will be required., Ventilated, Fans, or AC units.

Some Items to look at, Enclosure Surface Area

For very hot modules, use an air deflector, air routing products help to ensure consistent climate control throughout your electronics enclosures.

Vent clearance is important and often as additional items are installed or left behind the Enclosure/Cabinet the vents get blocked.

Recommendation: Keep clearance at 300 mm

Typical Faults

After installation some basic items should be physically looked at and corrected before the components are powered up. Most common are covered vent slots and can be corrected fairly easy with the correct cable lengths and wire trays.

I also find that air inlets are covered and you will find all sorts of items blocking them such as spare parts, documentation,tools, and more. Consider a document holder on the doors, or side panels, enclosure manufactures such as Rittal support quite a bit of weight on the side panels and doors.

As the density of the electronics inside increases heat load and cooling the internal electronics requires air flow patterns inside the cabinet.

Some installations use natural convection in the enclosure and works well when the enclosure has a few heat-generating components and the outside ambient air is cooler. Fans can be used used to move air through the cabinet but in the case of contamination from harsh environments, enclosures will most likely be sealed and any outside air will be filtered.

In review

Cabinet Heat Load: The total heat load in the Enclosure/Cabinet, determines what type of enclosure cooling will work. 

Equipment heat load: This is the heat generated by the internal components mounted inside. Higher density equipment generates a significant amount of heat.

External heat sources: When installed outside Enclosure/Cabinets are exposed to temperature swings, which can increase the heat load by more than 20 percent.

Ambient temperature: In the summer ambient air temperature can top 104 °F in many parts of the country, becoming another heat load variable.

Together, these factors can cause the internal temperature of outdoor cabinets to reach extremely high levels unless effective cooling solutions are used.

Recommendation:

Look for vendors who can provide temperature evaluations. Rittal has a program to evaluate your climate control proving a useful view of your installed Enclosure/Cabinets.

Additionally use a calculation program for the climate control of enclosures like Rittal's Therm software package. It guides you to the most suitable, climate control component. At the end of the calculation, you receive detailed documentation that you can either print out.

At a minimum physically inspect your Enclosure/Cabinets, look for blocked vents, evaluate duct systems to direct the air flow.

Rittal invites you to learn more at: www.Rittal.us