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An office block in Manchester is set to save over GBP29,000 on its annual electricity bill following the installation of ABB variable-speed drives on its HVAC system.

For several years, Jackson House had air flow problems throughout the tenanted areas.

One such problem was that the main ventilation plant’s fans were running constantly at full speed.

The plant consists of four fans, ranging from 45 to 120kW; two for supply and two for extraction.

The block also has a variable-temperature heating system comprising four pumps; two duty pumps and two standby pumps, also running at full speed.

Another problem was the high noise level of the fans.

Local residents living near the office block had instigated a noise abatement order, which restricted the operation of the plant to certain times.

This in turn restricted the letting potential of the property.

Part of the refurbishment of the office block involved the installation of a BACnet-based Building Energy Management System (BEMS) from the Canadian manufacturer, Delta Controls.

Staffordshire-based Building Environment Control (BEC), which installed the BEMS, were asked to install variable-speed drives that could be integrated with the control system to improve the management of the building’s ventilation.

Nick Payne of BEC says: ‘ABB drives are straightforward to program with a simple menu structure that makes them easy to set up.

‘A big advantage is that they include the flexibility of inbuilt BACnet compatibility.’ BEC’s analysis of the fans and heating pumps’ duty cycle was based on 2,600 hours per annum, assuming an electricity cost of GBP0.07/kWh.

For the air handling fans, installing ABB HVAC drives on each of the four fans resulted in a 49 per cent energy saving.

This equates to annual cost savings of between GBP4,000 and GBP10,700 per fan, depending on rating, giving a total saving for the air handling unit of GBP27,914 per annum.

The payback period is about 11 months.

The pressure control of the fans is improved and allows accurate air balance to be achieved on the floors, reducing noise, draughts and improving temperature control.

Similarly, the heating system pumps save GBP1,572 per annum following installation of ABB HVAC drives.

Another benefit is the improvement in the pressure control of the pumps, allowing accurate water balance to be achieved on the floors.

In a way similar to the air handling fans, this will reduce noise and improve temperature control.

Additional energy savings are achieved as heating will only be pumped around the building when it is required to match the building demand.

‘Soft start’ is another standard feature of the ABB drives, which provides a controlled slower startup to minimise electricity peak demand.

Peak demand is normally penalised by electricity providers and can affect the tariff set by the utility provider.

ABB Automation Tech – Drives and Motors

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