For example, a pump and fan control feature enables one drive to control several pumps and fans, and an automatic start feature ensures fast reconnection of freewheeling fans and pumps, should a power interruption occur. The AC drive also has a high power factor and no reactive power compensation is needed, avoiding the need for power factor correction equipment and the risk of penalties from the electricity supplier. It also includes soft start, which reduces the stresses on mechanical components, reducing maintenance, and enables starting of air conditioning compressors without manual adjustment of inlet vanes and piping valves. Intelligent drives that plan ahead Variable speed drives can also introduce new features to the HVAC system. For instance, if the contract with the electricity company stipulates that only a certain amount of power may be drawn during peak hours, the drive can be programmed to temporarily lower the capacity of the HVAC system to avoid penalties.
Drives can also help apply a more comfortable indoor climate.
Studies have shown that people prefer slightly drier and cooler air in the winter and slightly warmer and more humid in the summer. The drive can accept signals from outside sensors and achieve this automatically. Many HVAC systems today are overacting, causing unnecessary cool conditions in the summer and too hot in the winter, which makes people uncomfortable and wastes energy. Correct humidity is also important from a health point of view, as bacteria and viruses thrive when the relative humidity is below 40 per cent or above 60 per cent. Humid air also requires more energy to heat than dry air, so from an energy efficiency point of view, correct humidity is important.