FEATURE ENCLOSURES
How to check that the cooling output inside an enclosure is sufficient
Jason Swann, product manager for Climate at Rittal, offers some practical tips on how to evaluate an enclosure’s climate control through a series of simple checks
an insufficient output and suggests that there is likely to be a deficiency in suitable cooling air to the components inside the enclosure. The activity of the refrigeration compressor during cold production is
accompanied by a slight vibration of the refrigerator housing, which can easily be felt. Therefore, you can simply touch a device to determine a refrigerator’s operating status. 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°C and 40°C) than the ambient temperature.
M
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. Without this, the impact can be harmful to the inverter drives, power supplies, contactors, PLCs and other electrical and electronic components operating within them. Like all electrical equipment, drives create heat and therefore have a
major influence on the temperature inside an enclosure. Drives are often quoted as having efficiency of 97 per cent, so one with a rated output of 150kW can produce as much as 4.5kW of heat. As well as the heat loss inside the enclosure, ambient temperatures within a production facility will also have an 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 under all the ambient conditions that could be met at the machine’s location.
CHECKING THE TEMPERATURE The first check is to measure the temperature within the enclosure to assess its climate control capability. Temperature sensors should be placed in a position within the airflow of the enclosure and should not be placed on or near direct airflow from high temperature components. Otherwise temperature readings can be found to be inaccurate. The sensors should be left to monitor the temperature trend over a 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, alternatively, that there has been a malfunction of the cold air routing in the enclosure. This means that the cooling air cannot reach the temperature-sensitive components.
CHECKING THE CONTROL BEHAVIOUR OF COOLING DEVICES Another 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 new Rittal ‘Blue e+’ cooling units, conventional enclosure cooling units begin with the two-point regulation of the cooling operation - when the temperature inside the enclosure gets above 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 is a good indication that the cooling unit has
1 MAY 2017 | ELECTRICAL ENGINEERING 8
LOCATING HOTSPOTS You can also do a rough check of an enclosure’s climate control system with infrared thermography, which measures the surface temperatures of the components inside the enclosure. 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
www.rittal.co.uk
ATEX IP68 FRAME AXIAL FAN
Following extensive market research, the Axair Group, which is made up of Axair Fans and Axair Refrigeration, have developed and now stock ATEX IP68 Frame fans. The product is not only ATEX (explosion proof) but is EC, meaning the new product uses 80 per cent less energy than its AC counterpart, keeping in line with Axair’s strong social responsibility policy and goals to reduce customers energy consumption. The Axair branded fan is 120 x 120 x 38 and is available in three
speeds. The fan can be used in a whole host of applications including commercial refrigeration, electronic cooling and enclosure cooling. Axair continue to operate in a large section of the industrial and OEM market, catering to applications such as thermal management, fume extraction and Biomass, in addition to General HVAC components. Managing director, Grant Edwards, comments: “Following the
launch of Axair Refrigeration, our focus has been on delivering products that the market needs. The Launch of our ATEX IP68 compact axial fan fills a gap in the market that is required in many potentially hazardous applications.”
Axair Group
www.axair-fans.co.uk
/ ELECTRICALENGINEERING
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