✅ Boiler flow meter.✅ Instructions for use: Set the scale slider to the appliance's nominal flow rate.✅ Let hot water run into the container, moving the slider until the water inlet and outlet stabilise without overflowing.✅ At that moment the slider will show the appliance's consumption flow rate in litres per minute.✅ Calculation formula.: Useful power = Atº x 60 minutes x litres H2O.