During an audit of the BMS controls function of a four storey building in Gatwick Airport it was discovered that the chilled water plant (rated at 250kW input power) was being triggered by a fixed-time regime and that frequently, the chilled water plant was being enabled when no demand existed.
The principle observation that confirmed this was a very minor temperature differential between the flow and return temperatures that was mainly attributable to pipework losses, rather than actual plant demand.
A review of the software revealed that the only interlock present was a low-ambient hold off setting.
The software control was modified to include demand logic from Fan Coil Units (FCUs) and Air Handling Units (AHUs).
It was established through the monitoring and normalisation of electricity consumption that this enhancement of the software resulted in an 8% reduction in the chilled water electrical load over the year.
Measurement of Savings Achieved
Annual Energy Reduction = 55,000kWh
Annual CO2 Reduction = 30 tonnes
Annual Cost saving = £4,400
Cost of implementation = £1,500
Return on Investment
Payback period = 4 months