Control cabinet cooling to exhaust warm air

Cabinet cooling lets electronic components live longer

With a cabinet cooling with fan, the cool outside or ambient air is filtered and then sucked in by fans in the lower area. Inside the cabinet, the clean air is routed through the heat-emitting internals. It absorbs the waste heat of the components. The heated air rises automatically and is pushed outwards via an outlet grille installed in the upper part of the control cabinet. The control cabinet creates a permanent overpressure that prevents the ingress of dust and contamination. The greatest possible distance between the air inlet and exhaust air device increases the service life of the components. The performance and durability of the installed parts are significantly affected by the advent of dust. As a rule, the devices installed in the control cabinet are designed for a maximum operating temperature of 50 degrees Celsius. As this temperature increases, the life decreases and the performance decreases. Even a slight reduction in the temperature inside means a longer life and better performance. For the correct design and calculation of the air volume for ventilation and cooling in the control cabinet, the required air volume must be calculated. The following values are required for the heat calculation:

• Watt: Thermal heat emission of the installed devices in the control cabinet, also called power loss.
• degrees Celsius: Maximum allowed temperature inside the cabinet.
• Degrees Celsius 2: Maximum ambient temperature outside of the cabinet.
• Air Constant: This is expressed in Kw / h and refers to the decreasing / decreasing air pressure as the altitude rises above sea level.
• HxWxD: Cabinet dimensions or effective surface. Decreases when multiple cabinets are side by side.
• k: Heat transfer coefficient depending on the material used to make the cabinet = 5.5 for painted or coated sheet steel, 3.7 for stainless steel, 12 for aluminum, 3.5 for plastic and polyester, and 2.5 to 3.5 for wood.
• Qt (Pv): Power loss of the installed component.

In addition, the calculation should take into account day and night temperatures as well as differences in the temperatures due to seasons and climatic zones.

Passive cooling in the control cabinet has limits

The passive control cabinet cooling takes place solely via the outer walls and does not require any additional equipment. It usually takes place via ventilation slots in the housing walls. In order to prevent heat build-up, users often only have the option of banishing hot components from the control cabinet to the outside. But limits are set to cool the cabinet with passive cooling. Passive cabinet cooling works best when the outside temperature is significantly lower than the inside temperature. As a rule, passive cooling is only possible with small control cabinets. Optionally, the enlargement of the control cabinet is possible with the same components. But here, too, the natural limits of temperature equalization are quickly reached.

Control cabinet cooling with fan

The active cabinet cooling can be carried out by means of air or cooling water. For this, additional devices must be installed in the control cabinet, such as filter fans, cooling units or air / water heat exchangers. For filter fans it is important to clean the filter regularly. For this, it must be removed, washed out or renewed if necessary. Corresponding instructions can be found in the operating instructions of the manufacturer. Active options also include the use of air / air heat exchangers, air / water heat exchangers and refrigerators. Active cooling in the control cabinet has many advantages, such as:

• Ensuring the constant air temperature.
• The improved performance of the components.
• Compliance with the statutory IP degree of protection.
• The longer life of electrical components.
• Keeping the air clean through high-quality filter fans.
• Small footprint and easy installation.
• Pressure-stable and even cooling.

High cooling efficiency is becoming increasingly important

Refrigeration cabinet manufacturers have increasingly invested in new products in recent years. The development has focused primarily on the efficiency of the ventilation motors and the optimal air distribution in the control cabinet. Other criteria are often a low noise level, high pressure build-up, high air output and high efficiency. Depending on the manufacturer, there are fans that move the air in the axial, radial or diagonal direction. At one of the leading manufacturers there are different designs for fans to find. In doing so, the company is responding to the growing demands of customers for efficient and powerful cooling of control cabinets and server racks. Filter-free fans with standard protection IP 54 are suitable for tool-free mounting. Optionally, customers can also get this model with an EMC shield. Depending on the requirement, control cabinet cooling can be either

1) As a complete fan unit for tool-free installation with air capacities from 20 m³ / h to 900 m³ / h,

2) As a complete fan unit for tool-free installation in areas with air capacities from 20 m³ / h to 900 m³ / h, or

3) As an energy-efficient version with tacho signal for controlling and monitoring the fan with air capacities from 55 m³ / h to 900 m³ / h.

Above all, fan units without installation effort are popular with customers

They have a number of advantages, such as:

• Fast mounting on the cabinet without tools in just a few easy steps.
• Quick change of the air delivery direction by turning the fan module.
• Fast filter mat change due to lamellar grid mechanism.
• Electrical connection via cage clamp without tools.
• Higher energy efficiency through pressure-resistant diagonal fans.
• Effective prevention of hotspots.
• Individual positioning of the voltage connection.
• Constant air flow when installed and with dirty filter mat.
• Diagonal discharge direction to the outside ensures uniform air distribution.
• Low installation depth.
• Reduced maintenance intervals.
• Flow-optimized air flow.
• Inexpensive possibility of cooling.

Homogeneous climate in the control cabinet prevents hotspots

While ever smaller components and power electronics are hidden in the control cabinet, the problem of heat loss has not automatically decreased in parallel. The thermal stress on the components leads to shorter life and reduces the performance of the components. Customers especially want a small-sized cooler unit and efficient cooling performance. A typical mistake often shows in the oversizing of cooling units and that these are powerful but also energy hungry. Flow-optimized coolers ensure that it can not come to the extremely high temperature and heat, the so-called hot spots, in the control cabinet. Air standstill in the control cabinet must be prevented in any case, because the air circulation is essential for the uniform heat distribution. The more efficiently the heat can be released to the environment, the lower the risk for hot spots. In addition to the hot spots, so places in the control cabinet at which particularly high temperatures can occur, there is also the risk of heat testers. One more reason for the use of efficient cooling in the control cabinet and server rack. Due to the increasing power loss of the electrical components with poor cooling, dangerous heat esters are frequently formed. If several heat-producing components are spatially tight, then the heat problems can multiply. Quick local temperatures of up to 100 degrees Celsius are possible. Heat testers result from the renewed intake of already discharged hot air. This affects above all the upper areas in the control cabinet, while the components in the lower housing part are sufficiently cooled. The so-called Kaltganghausung prevents the discharged hot air passes through gaps in the cooled interior of the cabinet. When installing the control cabinet ventilation, this technical feature must be taken into account. Setting the correct temperature for the air in the so-called cold gear prevents the formation of hot spots.

Cabinet cooling provides more power and longer service life

Just one degree less inside the control cabinet can significantly increase the efficiency of the components. The data center feel-good temperature is BITKOM from 22-27 Centigrade. In addition to the impact on efficiency, the control cabinet cooling makes sense also from environmental aspects, because the longer the components are in operation, the less hardware has to be produced and purchased.