Controlling efficiency

Saving energy costs instead of building up excess pressure – this was Wilo’s primary objective in the development of p-v synchronous control. The new control mode represents a major step towards meeting future legal thresholds for energy efficiency according to the energy efficiency index (EEI). “Due to the extension of the already available operating modes with p-v synchronous, the energy efficiency of the entire system is optimised. This way, unfavourable operating conditions can be avoided”, explains Product Manager Roman Zielinski. “The control mode p-v was developed under the premise that pipe friction losses of the system to be supplied are in a positive correlation to the volume flow.” This means that at low volume flows the likewise lower pipe friction losses can already be compensated by a lower hydraulic power. Instead of a horizontal constant pressure curve, the system moves along a pressure-variable straight line as a function of the volume flow, the gradient of which can be parameterised in the switchgear. This is done by defining the pressure set point at zero flow rate relative to the set point at maximum flow rate. The new mode is standard on SiBoost Smart Helix VE, SiBoost Smart MVISE and SiBoost Smart Helix Excel boosters.

Optimal combination for energy efficiency

The control mode consists of two parts: the p-v control and the synchronous operation. Compared to p-c control (constant pressure), p-v control discharges pressure changes linearly with flow rate and thus ensures a variable pressure. Due to the lower discharge pressure in the partial load range, power and energy can be saved – at the same time there are fewer pressure fluctuations at the tapping points. The new synchronous operation, which is integrated in the multi-pump systems at the same time as control mode p-v, optimizes the operation of several pumps with regard to overall efficiency and susceptibility to faults. In contrast to the already known "Vario" operation, the speed-accurate control is not only performed by the peak load pump, but by all active pumps at the same speed. “With the previous procedure, the pumps were started up gradually which means that one pump was most of the time running at a lower speed than the others. All pumps running at the same speed is not only energetically more sensible, it also consumes less power and is more hygienic, as there is no more “stirring” at minimum speed without flow”, says Zielinski. Depending on the number of pumps and the pump type, the EEI can be reduced between 9% and 11% by using the p-v control mode. A further reduction between 5% and 7% is then made possible by synchronous operation. Thus resulting in an overall reduction of approx. 16% - which is a big step towards meeting future efficiency thresholds on the European and international market. This means an average reduction of energy consumption and energy costs by 16%, which represents both a considerable economic and ecological advantage. In addition, the new operating mode minimises noise and vibration levels: "Our tests with the new control mode also showed that we were able to reduce vibrations in the plant, which of course also means less wear and tear on the components," explains the Wilo expert. "For more comfort, the noise level during operation is also significantly lower, as the pumps have to run at maximum speed much less frequently".

Always in control – the Wilo Assistant

The pipe friction losses and thus the correct setting of the control curve are different for each building - the Wilo Assistant (app) with the integrated tool “Set-up optimiser SiBoost” offers a simplified calculation and outputs the percentage value of the zero flow pressure compared to the nominal pressure to be set as the result, typically between 75% and 95%. During the first quarter of this year an introduction and short instructions will be published. The Wilo Assistant delivers the whole world of highly efficient pump technology on smartphones and tablet PCs of HVAC installers and TGA planners. The free app Wilo Assistant is an easy-to-use mobile application and supports planning, customer advice and installation.