Conventional damper and inlet guide vane control systems are increasingly being replaced by variable speed control systems. There are understandable reasons for this, as energy consumption during variable speed control is only as high as actual required during operation. This results in energy savings and an improved energy balance sheet.


Damping with a damper or louvre damper is the easiest way to reduce flow, but the most inefficient in terms of losses. The further the damping elements are closed, the greater the pressure loss. Whereas the additional resistance alters the plant characteristic curve, the fan’s power requirement curve remains unchanged.

Inlet guide vane control generates a pre-whirl through adjusting of the guiding vane. Both the plant characteristic curve and power requirement curve of the fan are altered, relative to the adjusting angle and swirl.


100 % needs-based consumption

Linear control characteristic 

Quiet running

Perfect start-up behaviour

Mechanical smoothness 

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In variable speed control, the pressure is only increased by the exact amount at the respective operating point needed by the system as resistance to realise the required volumetric flow. In ventilation systems with a parabolic characteristic curve, this means savings in excess of 80 per cent at individual operating points without any reduction in efficiency.

REITZ fan systems with variable speed control consist of three precisely coordinated components. Additional costs for the variable speed control system amortise on average within two years through the savings effects.

Existing ventilation systems can be retrofitted with variable speed control during partial modernisation. Talk to your → REITZ Retrofit contact!