Grundfos Pumps keep up pressure in new Rosebank blocks

To reliably serve the water needs at three recently constructed multi-story apartment buildings in Rosebank, Johannesburg, ACS Consulting Engineers has installed a range of the latest pumping solutions from Grundfos.

Reaching heights between 10 and 22 floors, the three buildings required domestic water reticulation, hot water production and drainage solutions, according to Willem Strydom, senior design engineer at ACS Consulting Engineers. “The domestic water supply throughout the buildings required pressure boosting due to the building heights and insufficient municipal pressure,” says Strydom. “A break tank in the basement of each building was used to disconnect municipal pressure – and will also limit the impact of any water outages.” In terms of the system design, Grundfos vertical multistage booster pump sets were installed to transfer water from the basement tank to a secondary roof storage tank. This increases the storage capacity during water outages, while boosting pressure due to the geodetic height of the roof tank.

“A second Grundfos booster pump set – with its suction connected to the roof tank – was then situated in the basement plant room to supply hot and cold water throughout the building,” he explains. Water heating is achieved by heat pumps in one of the buildings, and gas boilers in the other two, with open hot water tanks used as ‘batteries’. For this application, Grundfos TP hot water circulating pumps – which are vertical in-line units – circulate water from the tanks through the boilers and back to the tanks. “This keeps a constant temperature of 55 to 60 degrees Celsius in the tanks,” he says. “Water is circulated from the hot water storage tanks through heat exchangers using Grundfos TPE pumps.” These Grundfos TPE units feature an on-board variable speed drive incorporated into the motor, says Nick Pluck, associate sales engineer CBS South Africa at Grundfos. This allows for automatic or manual set-points to speed up or slow down the motor to achieve the required pumping duty. “If the temperature drops, therefore, the pump can accelerate to maintain the necessary temperatures in the hot water supply system,” says Pluck. “Conversely, it runs slower as the hot water supply temperature to the building rises. This increases the energy efficiency of the system by reducing pump speed during low hot water demand periods.” Thermostatic hot water balancing valves are used in conjunction with the hot water circulating pumps to increthe ase effectiveness and efficiency of the circulating pumps. The contract also required a solution to the risk of flooding in the building basements, in the event of heavy rain or a leak in the water storage tanks, says Strydom. “The underground parking basements, where the plant rooms are situated, are all well below the municipal sewer