Energy-efficient pumping
With energy costs on an upward trend, Glynn Williams discusses the benefits of variable-speed pumps in hydronic systems.
Despite fluctuations in energy costs, the general trend is upwards, so it is necessary to make sure that the specification choices made regarding major mechanical items in commercial buildings will deliver the best solution.
For many years pumps and pumping systems have been oversized. To overcome this problem, pumps and pump systems have been throttled back during commissioning to get them into the operating range required to match the system requirements.
We are all aware that speed-controlled solutions in variable-demand applications save enormous amounts of energy (and therefore money) as well as increasing comfort levels. A wide range of such pumps is now available to the market. A lot of recent improvements can be attributed to developments in software that can change the performance curve of a pump to operate as required within any given situation.
Controlling the speed of a pump can be achieved in a number of ways, including using frequency converters — a technology used by Grundfos for almost 25 years and which became integrated into pump solutions in the early 1990s with the development of its first e-pumps.
The benefits of increasingly intelligent software can be seen not only in integrated pump solutions, but also in other associated pump equipment. An example is where, for a whole host of reasons, consultants, either by choice or through necessity, continue to select fixed-speed pumps and use external frequency converters to gain the control required.
This technology has just been taken to new levels by the latest addition to the Grundfos e-solutions pump programme — the CUE. This product is a versatile, wall-mounted frequency converter with e-pump functionality. It is applicable to new applications involving Grundfos pumps, but can also be retrofitted into a whole range of applications where an integrated system either will not fit, is undesirable, is prohibited or the pumps required are above the usual 22 kW e-pump power range.
The CUE range offers a built-in PI controller that offers the same functionality and user interface as e-pump solutions, and has a hundred different configuration possibilities covering a power range from 550 W to 250 kW. The range offers five different power supplies, two enclosure classes (IP20/21 or IP55) and 24 different output powers.
The range brings the advantages of speed control to many installations previously not covered by e-pumps — including: submersible installations, wastewater, water supply, ATEX (explosive atmospheres) areas and sanitary installations.
To keep things as uncomplicated as possible the CUE makes installation and commissioning a simple operation. Only a few settings need to be specified by the installer on site as the rest of the set-up is either done automatically or is pre-set at the factory.
These frequency converters have an operating panel with a graphical display with a backlight and buttons that control start/stop navigation and menu settings. Another plus means that these solutions automatically detect the rotation during set-up and ensure the pump always runs in the right direction.
These units can be fitted retrospectively to fixed-speed pumps that only need to operate at part-load.
Booster sets also benefit from such smart software. For example, Grundfos Hydro MPC booster systems have control systems to assist with all the operational requirements from installation to operation, and beyond, for up to six pumps in parallel. The CU 351 will control the number of pumps in operation, the speed of each pump and automatically adjust the performance of the system to meet the variation in demand.
The control unit has an installation wizard to guide the user through a series of steps that ensures all settings are completed in the correct sequence, which in turn means that the system performance — as well as any required protection settings such as water-shortage protection — are set up step by step.
These booster sets can be linked via a BMS to a remote computer for continuous monitoring and data collection on a huge range of operational areas, including system performance and energy consumption. Controllers can also be prepared to communicate with a wide range of different protocols.
The increasing sophistication of software combined with advanced pump technology increases the options for tailoring pump solutions to meet specific demands.
Glynn Williams is director of sales for commercial building services with Grundfos Pumps Ltd.
