Variable-speed drives are a certain energy saver
An office block in Manchester is looking forward to a £29 000 reduction in its annual electricity bill following the installation of ABB variable-speed drives in its HVAC system.
For several years, Jackson House had suffered problems with air flow throughout tenanted areas.
A particular problem was that the fans in the main ventilation plant constantly ran at full speed. The plant has four fans — two for supply and two for extract and rated from 45 to 120 kW. Constant running at full speed created so much noise that local residents had instigated a noise-abatement order to restrict the operation of the plant to certain times, which restricted letting potential.
The building also has a variable-temperature heating system with two duty and two standby pumps, which also used to run at full speed all the time. During refurbishment work, a BACnet-based building-management system from Delta Controls was installed. Installer Building Environment Control was ask to install variable-speed drives that could be integrated with the new control system to better manage the ventilation.
Nick Payne of BEC tells us that the ABB drives on the air-handling fans resulted in a 49% energy saving — amounting to £27 914 a year, based on electricity at 7 p/kWh, and a payback period of about 11 months. The pressure control of the fan has been improved, enabling accurate air balance to be achieved on the floors.
Energy savings for the heating-system pumps amount to £1572 a year. Other benefits include improved pressure control of the pumps, enabling accurate water control on the floors.
Soft start, a standard feature of ABB drives, minimises the peak demand of electricity.
Nick Payne comments, ‘The ABB drives and the Delta BMS were very easy to integrate with each other, and the building remained occupied during the installation period.’