The festive season was just around the corner and the temper­a­tures in Vander­bi­jl­park, south of Johan­nes­burg, made it seem like it was summer. It was bad news when the cold water system in Pick n Pay branch, one of the largest South African super­market chains, reached the end of its service life at this time: sweaty Christmas shop­ping trips and major conver­sion measures were not an option for Pick n Pay.

However, the condi­tions in the oper­ating room did not make it easy for Douglas Scott, Mechan­ical Engi­neer at refrig­er­a­tion and air condi­tioning company HCM, to bring the system up to date with a vari­able refrig­erant flow: Pick n Pay wanted new, energy-saving air condi­tioning and EC fan tech­nology. A partic­ular chal­lenge was that, previ­ously, a single large centrifugal fan sucked air in through the heat exchangers in the oper­ating room, supplying the existing pipe system and consuming a large amount of energy in the process.

More power under the same ceiling

But replacing it was not so easy: the fan was located in the middle of the spacious room, which had a suspended ceiling. Scott explains, “A typical FanGrid was ruled out because any pres­sure built up in the room would simply escape through the ceiling. In addi­tion, we would have had to extend the fan wall either up to the ceiling and change the ceiling design, or alter­na­tively build a smaller fan room and modify the existing cable system.” There were no options, consid­ering the time-consuming conver­sion measures that would disrupt busi­ness.

Turning one into nine: Where once a single large centrifugal fan sucked in air via the heat exchangers and supplied the existing duct system, now there is a fan cube with nine new power packs. (Photo | HCM)

But Scott had an idea: why not use the old centrifugal fan’s existing housing? After all, it was already connected to the pipe system. It was big enough to fit in and offered plenty of space on the flat side walls for the ebm-papst fans’ panels, which are easy to install. If a FanGrid would not work, what about a cube?!

The dice are rolled

Dewald Hattingh, Sales Engi­neer at ebm-papst South Africa, was on hand to imple­ment the ambi­tious idea, “We consid­ered many reasons why a fan cube would not work, but, in the end, HCM and ebm-papst estab­lished a theory that, as pres­sure sources, the fans would generate pres­sure that was turbu­lent yet so high that the fans would fulfill the system’s flow require­ments,” says Hattingh.

In the housing of the old centrifugal fan, nine RadiPac EC fans now ensure the right temper­a­ture in the chilled water system. This makes shop­ping fun again. (Photo | HCM)

There was not much time for simu­la­tions, so it was impor­tant to find out quickly whether the theory would work in prac­tice or the nine RadiPac EC fans in the cube would work against each other. But every­thing went well: the cube works perfectly.

Scott sums up: “The project would not have been possible without the impec­cable service from ebm-papst South Africa. The expert personnel supplied HCM with soft­ware and hard­ware and provided invalu­able advice on the possible prob­lems that could occur when using fans in this uncon­ven­tional way. They worked with HCM to test the solu­tion in the field, provided local stock to ensure a quick turn­around, and provided support with commis­sioning the system.”