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Energy-effi­cient fans for refrig­er­ated cabi­nets in super­mar­kets

Eco-refrig­erant for use in super­market refrig­er­ated cabi­nets can become highly flam­mable during malfunc­tions. EC fans have set new stan­dards in the fields of safety and effi­ciency.

The fans used in refrig­er­ated display cases and bottle coolers in the commer­cial food sector have very long oper­ating times; and so they offer great poten­tial for saving energy. Thanks to their high effi­ciency levels, EC fans have set new stan­dards in this field. Versions conforming to the Euro­pean stan­dard EN 60335-2-89 are even suit­able for appli­ca­tions involving the use of flam­mable refrig­er­ants such as R290 (propane), which can form explo­sive mixtures with air in the event of malfunc­tioning. What’s more, their intel­li­gent networking capa­bility simpli­fies servicing and main­te­nance. Fans have become indis­pens­able features of super­mar­kets, as the compact refrig­er­ated cabi­nets for medium and low temper­a­ture refrig­er­a­tion systems could not operate without them. On the one hand the fans ensure that the air circu­lates around the device, thus keeping all the stored prod­ucts equally cool. In plug-in refrig­er­ated cabi­nets they are also used to dissi­pate heat to the surround­ings, or to the central condenser in the case of so-called remote systems. Up until a few years ago, shaded-pole motors were the stan­dard method of driving the fans. There were good reasons for this: Such motors are cheap to make, robust and long-lasting. Their low level of effi­ciency of just about 20% however means that they are no longer accept­able these days. They have a high current consump­tion and also produce waste heat that has to be dissi­pated from the refrig­er­ated cabinet. And so the use of shaded-pole motors is now gener­ally restricted to just a few niche appli­ca­tions.

The energy-saving solu­tion: EC motors as the driving force

Picture 1: Oper­ating with an effi­ciency of more than 70%, the power consump­tion of the ESM motor is only a third of that of a compa­rable shaded-pole motor and it offers the option of demand-based speed control.

Instead, modern fan concepts are based on the far more effi­cient elec­tron­i­cally commu­tated EC motor, requiring roughly 70% less energy than the old motor design. As motor and fan specialist, ebm-papst has several such energy-effi­cient motor versions in its range that are posi­tively predes­tined to be used as fan drives in refrig­er­ated cabi­nets: More than ten years ago, the energy-saving motor – known as ESM – was already setting new stan­dards in fan tech­nology for refrig­er­a­tion appli­ca­tions (picture 1). Oper­ating with an effi­ciency of up to 70%, its power consump­tion is only a third of that of a compa­rable shaded-pole motor and it also offers the option of demand-based speed control. The lower power loss of the EC motor saves yet more energy in refrig­er­ated cabi­nets. It has a design service life of more than 40,000 hours, corre­sponding to approx. 5 years in contin­uous oper­a­tion. The compact EC motors are avail­able both as OEM compo­nents for combi­na­tion with a sepa­rate impeller and as complete plug & play systems with perfectly matching indi­vidual compo­nents. The axial product range with sizes of 130, 154, 172, 200, 230, 250 and 300 is intended for instal­la­tion beneath the shelves of refrig­er­ated and freezer cabi­nets. By contrast, the fans with diag­onal impeller of sizes 200 and 250 were designed specif­i­cally for instal­la­tion in the back wall of refrig­er­ated display cases, where instal­la­tion space is often at a premium (picture 2). Thanks to their extremely shallow design, these fans fit in confined spaces and the diag­onal fan design makes them well equipped to deal with the higher back pres­sure encoun­tered in such situ­a­tions. Tangen­tial blowers, which like­wise operate with EC motors and circu­late the cold air in the form of an air curtain, have also been success­fully used as effi­cient solu­tions for refrig­er­ated cabinet appli­ca­tions for many years now. These are partic­u­larly space-saving and quiet-running (picture 3).

Given the energy savings that can be achieved, it is even well worth converting older refrig­er­ated cabi­nets. ebm-papst can offer the energy-saving NiQ motor for this purpose (picture 4). Depending on the ambient condi­tions, the service life of the NiQ motor may exceed 40,000 hours. It is mechan­i­cally compat­ible with existing shaded-pole motors, has a high effi­ciency level of up to 70%, and its iden­tical instal­la­tion dimen­sions permit simple 1:1 replace­ment. Axial impellers with a diam­eter of 154 to 254 mm can also be fitted on the NiQ motor to provide a power-saving solu­tion.

Reli­a­bility: Keeping a constant watch on the fans

Along­side the lowest possible energy consump­tion, reli­a­bility is another impor­tant aspect with regard to refrig­er­ated cabi­nets in super­mar­kets. The 1.25 m long stan­dard elements are normally fitted with one to two fans. If a fan fails, it is impor­tant to localize and rectify the fault quickly without any adverse effect on the cooling chain and before any food perishes. Preven­tive main­te­nance and fan moni­toring are also useful.

Picture 4: The power-saving NiQ motor is mechan­i­cally compat­ible with shaded-pole motors and permits simple 1:1 replace­ment.

Networking via the serial inter­face for commu­ni­ca­tion via MODBUS-RTU is helpful in this case. It permits the imple­men­ta­tion of numerous surveil­lance, control and regu­la­tion func­tions in real time by way of remote moni­toring. For instance, it is possible to monitor motor oper­ating times with regard to preven­tive main­te­nance and to simply localize the fan concerned when service work is needed. Networking via the MODBUS-RTU commu­ni­ca­tion protocol also permits rapid adap­ta­tion to changes in oper­ating condi­tions, for example the cooling temper­a­ture can be attained more quickly after defrosting cycles by increasing the fan speed.

Does it really always have to be ATEX?

A further major issue with regard to refrig­er­ated cabi­nets is the refrig­erant used. Modern refrig­er­ants must be safe for the envi­ron­ment and have a low global warming poten­tial, whilst at the same time providing good refrig­er­a­tion perfor­mance. Since January 1, 2015 this has been regu­lated by the direc­tive (EU) 517/2014, also known as the fluo­ri­nated gas direc­tive. Along­side ammonia and CO2, natural refrig­er­ants such as isobu­tane, propane and propene are thus becoming increas­ingly popular as an ecolog­ical alter­na­tive to (partially) halo­genated refrig­er­ants. In the event of malfunc­tioning, the non-toxic hydro­car­bons can however form readily explo­sive mixtures with air.

Regu­la­tion (EU) 517/2014 on fluo­ri­nated green­house gases

Direc­tive (EU) no. 517/2014 on fluo­ri­nated green­house gases, also known as the fluo­ri­nated gas direc­tive, has been in force since January 1, 2015.

Motors and complete systems from ebm-papst are made to satisfy the require­ments of the Euro­pean stan­dard EN 60335-2-89 (house­hold appli­ance stan­dard) and so can safely be used for cooling appli­ca­tions in this sector. This is fully adequate for the majority of refrig­er­ated display cases, as their cooling circuits work with the 150 g maximum refrig­erant quan­tity set down by the stan­dard. Using ATEX compo­nents makes no commer­cial sense in such cases. It is also not suffi­cient to just use a motor with an ATEX label. The entire fan must have the appro­priate approval and the oper­ator has to define an explo­sion hazard area. The latter is often partic­u­larly diffi­cult to imple­ment in super­mar­kets. In the case of high-capacity refrig­er­a­tion circuits it may there­fore be appro­priate to split up the circuits. If that is not feasible, another prac­tical energy-saving alter­na­tive does exist with which users can be on the safe side even with refrig­erant quan­ti­ties exceeding 150 g: ebm-papst can also offer fans with an energy-saving motor with ATEX approval II 3G nA IIA T4. The fans are conform to the ATEX stan­dard EN 60079 and are there­fore also autho­rized for use in large refrig­er­ated display cases as well as composite and cascade systems.

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