FEATURE CABINETS, RACKS & ENCLOSURES
HOW TO CHECK COOLING OUTPUT M
Enclosures protecting delicate equipment need strictly controlled environments. Jason Swann of Rittal offers practical tips on evaluating climate control through a series of simple checks
anufacturing automation systems are delicate and very expensive
pieces of kit which perform vital functions for the businesses they serve. The enclosures that protect them must have strictly controlled internal environments with interior temperatures that are carefully maintained within a few degrees. If not, the impact can be harmful to the inverter drives, power supplies, contactors, PLCs and other electrical and electronic components operating within them. This requires careful control of the climate within the enclosure. As with all electrical equipment, drives create heat and they therefore have a major influence on the temperatures inside enclosures. Drives are often quoted as having efficiency of 97% so one with a rated output of 150kW can produce as much as 4.5kW of heat. In addition to the heat loss inside the
enclosure, ambient temperatures within a production facility will impact on the temperatures that a drive is operating within. A typical enclosure climate control system is designed for an internal enclosure temperature of 35°C. This means that the performance of a cooling unit should be specified so that the average internal enclosure temperature of 35°C can be guaranteed under all load conditions and ambient conditions that could be met at the machine’s location.
CHECKING THE ENCLOSURE TEMPERATURE The first check is to measure the temperature within the enclosure to
GRP INSPECTION DOOR FOR OUTSIDE ENCLOSURES
Intertec’s new GRP inspection door comes with a window frame made entirely from glass reinforced polyester offering a high degree of protection against corrosion combined with excellent thermal insulation. The design offers a more durable alternative to the conventional aluminium or stainless steel window frames commonly used for field equipment in harsh environments, helping to extend the lifecycles of business-critical process control and instrumentation equipment. Doors are available with IP54 or IP65 ingress protection. Intertec's GRP inspection doors are suitable for
enclosures and cabinets containing control and instrumentation equipment fitted with user interfaces, indicators and displays. This embraces a broad range of commonly-used field equipment including process transmitters and PLCs. A lot of this type of equipment is increasingly
being located deeper inside the processing areas of a plant where environments can expose the equipment to harsh and corrosive atmospheres. Two variants are available with window frames
measuring approx. 50x35 or 67x47 cm (19.7x13.8 or 26.4x18.5 inches). Intertec can fit these frames with acrylic safety glass or insulated glass panels to suit the application. Options include an insulated glass panel filled with Argon which has a significantly lower thermal conductivity than air. The U-value of the Argon-filled panel is 1.7 W/m²K. The inner glass pane features a heat-reflecting coating offering a g-value of 50% to reduce the impact of solar energy heat transmittance. An antistatic version of the door is available for hazardous area applications.
Intertec
www.intertec.info
period of time. If the sensor records air temperatures of well over 35°C (set point) then the output of the cooling unit should either be considered insufficient or that there has been a malfunction of the cold air routing in the enclosure. This means that the cooling air cannot (or only partially) reach the temperature- sensitive components.
assess its climate control capability. Temperature sensors should be placed in a position within the airflow of the enclosure not on or near direct airflow from high temperature components; otherwise readings can be found to be inaccurate. The sensors should be left to monitor the temperature trend over a
A rough check of an enclosure’s climate control system can be made using infrared thermography
CHECKING CONTROL BEHAVIOUR OF COOLING DEVICES A further easy way of checking an enclosure climate control system is to observe the cooling unit’s control behaviour. Unlike speed-controlled cooling devices such as the Rittal Blue e+, conventional enclosure cooling units begin with the two-point regulation of the cooling operation when a temperature inside the enclosure gets above of 35°C and finishes when the shutdown temperature of 30°C is achieved (at a typical hysteresis of 5K). If a cooling device does not reach the shutdown temperature a conventional cooling unit will therefore continue to operate. If this happens it’s a good indication that the cooling unit has an insufficient output and suggest that there is likely to be a deficiency in suitable cooling air to the components inside the enclosure. You can simply touch a device to determine a refrigerator’s operating status: the activity of the refrigeration compressor during cold production is accompanied by a slight vibration of the refrigerator housing that can easily be felt. Alternatively, the exhaust temperature of the cooling unit in the external air circuit may be measured. During active cooling operation this will be significantly higher (potentially, anywhere between 10° and 40°C) than the ambient temperature.
LOCATING HOTSPOTS
You can carry out a rough check of an enclosure’s climate control system with infrared thermography which measure the surface temperatures of the components inside the enclosure and these are recorded with an infrared camera. If any areas have significantly elevated
temperatures (hot spots) it is an indication that they are not being supplied with enough cooling air.
Rittal T: 01709 704000
www.rittal.co.uk
28 AUTUMN 2017 | IRISH MANUFACTURING / IRISHMANUFACTURING
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