Fruit and vegetable wholesaler relies on propane

GERMANY: A propane chiller has replaced an R404A refrigeration system at a fresh produce supplier’s warehouses in central Germany, reducing operating costs and improving the overall carbon footprint.

Family-owned business Fruchthof Northeim delivers fruit, vegetables, and fresh convenience foods to restaurants, catering companies, large-scale caterers, and food retailers.

The FrigoNatura propane liquid chiller from Frigotec GmbH was chosen for the first phase of the modernisation project of two cold stores.

Frigotec GmbH develops and manufactures the liquid chillers at its headquarters in Landsberg, Saxony-Anhalt. The liquid chillers of the FrigoNatura series have been optimised for the use of propane and are available in four capacity steps.

The chiller uses 4-cylinder Bitzer Ecoline Pro reciprocating compressors, specially developed for the particular requirements of hydrocarbon refrigerants.

The system supplies a total refrigerating capacity of 61.8kW, divided across two refrigerant circuits. The selection of fruit and vegetables, which varies depending on the season, is stored in two cold stores with a total area of 167m² and at a constant temperature of +4°C. This ensures that sensitive refrigerated good such as mushrooms, carrots, parsley and asparagus retain their high quality. 

Northeim is one of three Fruchthof locations in central Germany, handling a total of up to 15,000 tonnes of fruit and vegetables daily.

With the dismantling of the existing system being carried out gradually, the space available for the new refrigeration system was extremely limited – meaning that compact dimensions were required. 

The new propane liquid chiller is installed outside in front of the building. On the cold-brine side, the system is connected to two storage tanks, each with a capacity of 2,500 litres. The storage tanks are located in a separate machinery room set up as a container solution right next to the liquid chiller. The ethylene glycol is conveyed to the evaporators in the two Fruchthof cold stores via speed controlled pumps. Connections for additional pumps required in future modernisation work have been prepared in advance. Air cooled condensers have also been used in this project.

To allow a sustainable reduction in energy consumption and the associated operating costs, Frigotec focused on selecting energy-efficient system components, as well as optimised control technology. 

In addition to the inclusion of Bitzer’s IQ Module CM-RC-02, which optimises compressor installation, operation, maintenance and retrofitting, the system also includes a Siemens MLV702 magnetic expansion valve to ensure system stability and efficiency. 

The liquid chiller also features heat recovery, allowing the waste heat generated by the refrigeration system to be used for heating the building.

Frigotec uses Bitzer’s CM-IO-B Premium extension board in all liquid chillers in the FrigoNatura series. This means that compressors in the new Fruchthof Northeim system are equipped with application limit monitoring, a DP-2 differential oil pressure switch, discharge gas sensors, and additional temperature sensors to measure suction gas temperature and monitor wet operation. Varistep mechanical capacity control is also used for efficient part load operation. In the current application case, this facilitates a reduction in refrigerating capacity to 50% of the compressor capacity. In relation to the total refrigerating capacity of the liquid chiller, this results in a reduction of the total capacity to 25%.

In order to ensure safety with propane, the refrigeration system is equipped with a gas warning sensor, an exhaust fan and a warning light with siren. 

The Ecoline Pro compressors offer the advantage of enhanced tightness in accordance with EN1127-1, with no need to assume an ATEX zone around them.

Due to the sensitivity and high value of the refrigerated goods, the system control needs to be able to react promptly in the event of system failures. The system control, programmed by Frigotec, provides detailed insights into crucial system parameters at all times. Any error messages are forwarded directly via the Frigotec Connect app to ensure that appropriate steps can be taken quickly. In conjunction with the Bitzer’s BEST Software or app, the compressors’ IQ Module also allows continuous access to compressor operating data to support evaluation, analysis and optimisation. 

The installation of the refrigeration system was successfully completed within three weeks with no interruption to active operation. During this time, the goods from the two cold stores that required retrofitting were temporarily stored in a third cold store. Additional cold rooms will soon be upgraded in the same way to future-proof the site.