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How do variable-speed drives benefit HVAC cooling towers?

Variable-speed drives are used in a huge number of electric motor-driven industrial and commercial applications around the world. By accurately controlling electric motor speed, drives enable users to tightly regulate energy consumption in processes such as pumps, mixers, grinders and conveyors to name just a few. In addition, they’re an invaluable device in HVAC cooling towers. Read on as we explain.

What is a cooling tower?

A cooling tower is a heat rejection device that extracts waste heat to the atmosphere, normally by using air to reduce the temperature of circulating cooling water. When air and heated water come into contact, some of the water evaporates which lowers the water temperature. The cooled water is then pumped back into circulation where it absorbs more heat, and the process is repeated.

Where are cooling towers used?

Cooling towers are used in many heavy industrial applications including petrochemical plants, oil refineries and thermal power stations. They are also used as part of heating, ventilation and air-conditioning (HVAC) systems in office buildings, shopping centres and hospitals.

Why are variable-speed drives so useful in HVAC cooling towers?

Although electric motors can only run at their rated speed, the HVAC systems they drive rarely need to operate at 100 per cent capacity. This means that most of the time, HVAC equipment is wasting energy as the electric motor runs constantly. Traditionally, additional measures are used to control airflow such as cycling fans on and off or varying the pitch of fan blades. However, this is extremely inefficient and places strain on components.

Variable-speed drives enable users to control electric motor speed according to changing conditions, making them ideal for HVAC applications. For example, VSDs allow fan speed to be precisely adjusted, with just a 20 per cent reduction in speed cutting energy consumption by 50 per cent in many cases.

A VSD can also sense unwanted fan rotation, such as reverse movement due to windmilling. The drive will recognise that this is happening and slow the fan to a stop before rotating it again in the correct direction.

VSDs can be installed in new cooling towers as well as being retrofitted to existing applications, and along with saving users energy, they reduce wear and tear on the motor and HVAC system components.

Gibbons Engineering Group are the preferred supplier, installer and maintenance specialist for HVAC drives due to our considerable expertise in both fields. Not only do we have a dedicated HVAC Services division, with vast experience operating in the commercial and industrial sectors, we’re also an ABB Authorized Value Provider for variable-speed drives.

This exclusive position gives us access to a global network of products and expertise for ABB drives, allowing us to deliver state-of-the-art equipment within the shortest possible time, with a wealth of support available.

To find out more about the benefits of variable-speed drives for HVAC cooling towers, call Andrew Knight on 07850 204915 or email

HVAC Services, Variable-Speed Drives

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