Open-loop control or closed-loop control – what is the impact of this on efficiency and convenience?

iTechnology sets new standards, not only in terms of overall DHW convenience, but also when it comes to energy efficiency. Equipment levels "fully electronic closed-loop control", "electronic closed-loop control" and "electronic open-loop control" determine the stability of the outlet temperature and hence the degree of DHW convenience. The temperature at the draw-off point is influenced by various factors. These can be corrected by different sensors. The more “high end” the appliance, the more sensors control the water temperature and the more precisely the DHW temperature is maintained, which is particularly energy efficient.

4-fold intelligence for limitless premium comfort
For fully electronic closed-loop control, STIEBEL ELTRON relies on 4i technology. This combines three sensors and a motorised valve. The sensors capture the inlet temperature, outlet temperature and flow rate. Continuous set/actual comparisons ensure accurate temperature delivery. When the appliance is at its maximum output, greater DHW consumption could automatically result in a drop in temperature. To ensure that the required temperature is still maintained even in this case, the motorised valve automatically finely adjusts the amount of water delivered. This means no more unpleasant temperature shocks when showering. The process is totally automatic and not perceived by the user. This considerably increases the comfort factor, especially when several draw-off points need to be supplied at once. 4i technology maintains the required temperature with constant precision, regardless of showering patterns or external influences. There is no need to mix in cold water. As a result, only the actual energy required is used, which translates into high efficiency. STIEBEL ELTRON's premium model, the DHE SL electronic comfort, provides this exclusive level of comfort based on 4i technology.

3-fold intelligence for a high level of convenience
The appliances with electronic closed-loop control feature 3i technology. This comprises temperature sensors at the inlet, the outlet and a flow sensor. It enables the instantaneous water heater to maintain a constant and accurately held outlet temperature. In exceptional circumstances where the appliance is at maximum output – for example extremely low inlet temperatures in winter – the user can regulate the amount of water using the tap, to ensure accurate temperature delivery. 3i technology is also highly efficient overall, as only the amount of energy and water actually required is used. In this respect, it is on a par with the technology found in the premium class.

2-fold intelligence for everyday DHW convenience
The instantaneous water heaters with electronic open-loop control are equipped with 2i technology, comprising an inlet temperature sensor and a flow sensor. This system calculates the heating output required subject to the selected temperature. Up to three fixed temperature levels can be selected (approx. 35, 45, 55 °C). If a different temperature is required, the temperature can be manually adjusted by mixing in cold water. The energy efficiency of 2i technology is optimised to the energy consumption of the temperature levels.