By what percentage can the speed of the driven unit be varied with a variable drive?

When using a variable drive, the speed of a driven unit can typically be varied by a significant percentage, often up to 30%. This capability allows for greater control over the operation of HVAC systems, enabling adjustments to match the specific demand for heating, cooling, or ventilation in a building. Such flexibility is beneficial for energy efficiency and improved system performance.

Variable drives work by altering the frequency and voltage supplied to the motor, which in turn adjusts the speed of the connected equipment. This can lead to optimized system operation and reduced energy consumption when compared to fixed-speed operation. The 30% variation represents a common benchmark in many systems, allowing operators to effectively balance performance and energy use.

The other percentage options, while they might suggest varying speed capabilities, do not generally reflect the standard range provided by variable drives in HVAC applications, making 30% the most accurate choice for this context.