Article: Multi Air stream Technology - Biddle - #9

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Maintenance Depending on use and the humidity levels in the loading hall the unit needs to de-frost. This is done automatically when the cold store door is closing. Under normal conditions this should be done every 24 hours but at least once per 5 days of continuous operation of the MAT. After about 15 minutes of de-frosting the unit is ready for use again. The maintenance of the MAT unit is limited to a regular check if all fans are working properly. Depending on the location of use, an annual or bi-annual cleaning of the fans with high pressure air is all you have to do. The advanced controller can show a sequence of possible error codes and at any moment all kinds of parameters giving the status of the unit can be displayed. Picture 9 – 10: The difference between a standard air curtain (left picture – the doorway is filled with fog) and a MAT air curtain (right picture – the doorway is clear) Can the MAT be used under all conditions? There are a number of design guidelines which should be kept in mind to optimize the use of the MAT. The mounting height (and thus the maximum height of the cold room doors) is limited. Depending on the conditions of the loading hall this maximum mounting height can range between 3 and 4 meters. Higher doors require such a high volume of air to block the convection forces (and as a consequence a very high heating capacity) that the application of this technology becomes less efficient. A part of the B-stream heating needs to be cooled away by the cold store. Even though the MAT offers a fog free and clear doorway at higher mounting heights, the energy consumption involved to do so would be too high to create a costs effective solution. There is a trend in cold store design these days which incorporates higher doors, this to allow the use of higher forklifts. However, the energy loss through these high doors is enormous. 9