Case story. Focus on oil level control, a contributing factor in Advansor's success in the development and production of transcritical CO₂ systems.

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1 Focus on oil level control, a contributing factor in Advansor's success in the development and production of transcritical CO₂ systems. When Kim G. Christensen and Torben M. Hansen founded Advansor in 2006, they were particularly focused on the components needed to ensure unrivalled operational reliability... One of the greatest challenges in the design of CO₂ systems is ensuring refrigerant charge during down time. The system thus becomes easy to service, by a pump-down can be performed to the receiver. However, for ambient temperatures of up to 40 C, it means that the system must be designed for a pressure of approx. 100 bar, which must also be taken into account in the selection of sensors. Advansors transcritical CO₂ systems and HB Products sensors has been designet to the high pressure.

2 The oil carry over from the compressor in transcritical CO₂ systems is greater relative to systems with less pressure or other refrigerants. With the compressor sizes available today, the systems are most often designed with several compressors in parallel; therefore correct oil control in the compressor casing is essential for ensuring adequate lubrication and for avoiding damage. Case story CO2 refrigeration systems put great demands on oil management in the compressor "Reliability is of the greatest importance in our CO₂ systems, and we have realized that the HB Products sensors, which are used in all our systems, offer the best and most reliable option for monitoring and control, and therefore play a role in ensuring the longevity of the compressors," says Torben Hansen. Development of HBOC Oil Control Sensor in conjunction with Advansor Since there were no products on the market which matched Advansor's requirements, Advansor and HB Products began joint development in The goal was an advanced stand-alone sensor with level control for decentralised oil control. A further requirement was that it would be able to prevent compressor damage independent of malfunction or breakdown in the main controller. HBOC has been designet for the majority of compressor manufactures.

3 Development of HBOC Oil Control Sensor in conjunction with Advansor The result of the development collaboration with HB Products was a success. Today, we use HBOC for decentralized level control on our smaller and very popular "compsuper XS" models, which are our supermarket systems for smaller supermarkets. Apart from ensuring correct oil levels, it is cheaper and easier to install. It is also simple to setup the parameters" says Kim G. Christensen. HBOC offers a series of advantages, which makes it both unique and universal. It is designed with the focus on easy use and installation. A 24V power supply cable to the sensor is all that is required. The solenoid valve, which opens and shuts for the return of oil, is controlled and supplied directly from the sensor. Since HBOC is a stand-alone unit, there is therefore no need to install any extra "oil management" modules or special PLC programming, which typically are necessary when using common rack-controllers. "It has been an exciting development project, and HB Products has been very responsive to our requirements for easy installation and userfriendly PC setup. Today, we receive them pre-configured for the systems we have, so it is really a plug-and-play solution for us," says Mads Holst Nielsen, head of electrical department at Advansor. HBOC mounted on compressor with direct control of solenoid valve.

4 Specifications for HBOC Stand-alone principle: Making it simple and reliable Flexible: Can be used for level control on both compressors and separators Variable parameters: Oil cycle, alarm, open/close times, etc. Maximum pressure: 150 bar, usable with all common refrigerant oils Easy to connect: Directly supplies the solenoid valve for oil regulation Easy assembly: Can be mounted on all common types of compressors and oil separators Configurable: From a simple PC program, no training needed Also designed for use in oil separators During development of the sensor, we also took into account that it should be possible to use it for oil draining on oil separators. Using the PC program, the same sensor can easily be configured for use on separators. In this "mode", the variable parameters such as oil cycle, alarm, open/close times, etc. are also individually set up. "Since the product was launched in 2011, we have supplied more than 50 systems in which we have installed HBOC for oil control in each compressor all in all more than 180 HBOCs," says Kim G. Christensen. HBOC mounted on oil separator for automatic regulation of oil level.

5 About Advansor & HB Products Advansor develops, produces, and sells sustainable thermal systems for heating and cooling in Power plants, the food processing industry, the chemical industry, air conditioning of office buildings, and refrigeration in supermarkets. Advansor was founded in 2006 by Kim G. Christensen and Torben M. Hansen, both of whom have worked as managers at the Danish Technological Institute. In 2011, the company was acquired by Hill Phoenix, an American group with a wide range of competences within refrigeration. Read more at or The company is based in Århus, Denmark, and has more than 20 years experience in the development and production of electronic sensors for the refrigeration industry. The activities began in 1989 in the company Hans Buch & Co., upon the request of the world renowned refrigeration company, Sabroe A/S. HB Products is EN ISO9001:2008 certified, and can provide products that are certified to fulfil the requirements of ATEX, culus, and IECEx. Read more at