Enthalpy - In an air handling plant there is a point in time during hot weather when the outside air has more heat energy in it than the air which is already in the working space. An energy efficient control system should know this from the readings of its sensors. It should then switch the air damper system to recirculate a lot of the air in the building if cooling is required at that time. This causes the system to only cool down the recirculated air instead of the outside air to achieve a cooler building thereby saving chilled water energy. Often such a scheme is either not in place or not functioning correctly.

Fans and Pumps - Often these motors operate as a fixed speed system ( with or without a variable speed drive ). By installing a pressure sensor as well as a variable speed drive these motors can be set up to control automatically to a pressure set point. This causes them to run mostly at lower speeds than would be the case with a fixed speed scheme thereby quickly paying their way in energy savings.

Boilers - If there are two or more boilers in the building they should be set up to operate on water temperature controlled boiler sequencing. This means that only one boiler will operate in conditions of low demand. This prevents the standby boiler firing unnecessarily and wasting oil or gas.

Valves - The heating, ventilation and air conditioning system for your workspace may have heating and cooling valves as part of the control scheme. These valves should be able to operate correctly over their full range from tight shut off to fully open. This is known as valve stroking. In a poorly maintained scheme its is often found that a cooling valve may be partially open while a heating valve is also open thereby wasting energy unnecessarily.

Chillers - If there are two or more chillers in the building they should be set up to operate on water temperature controlled chiller sequencing. This means that only one chiller will operate in conditions of low demand. This prevents the standby chiller starting unnecessarily and wastefully using electricity.

Optimization - Time schedules or time switches can be replaced with optimizer schedules. Optimizers automatically work out what time to switch on the heating, ventilation and air conditioning plant in order to bring the temperature up (or down) to the exact temperature required just in time for people to occupy the building. This saves a lot of energy compared to the fixed time starting which is in operation in a lot of buildings.


De Stratification Fans - These fans are designed for high roofed buildings such as large retail shops to circulate the air from high up to low down in order to heat the space evenly. Without them all the heat would rise to the top of the space and the occupied space lower down may be too cold. They are often used in conjunction with unit heaters. They are sometimes found running unnecessarily due to a poorly maintained, designed or sited control system thereby wasting energy.
Swarpro Limited, 71-75 Shelton Street, London, WC2H 9JQ

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