Technical specifications: Operating voltage: 5 VDC Operating current: less than 10 mA Operating temperature: -25 °C to 70 °C (non-freezing) Make-up water flow rate: greater than 5 L/min at 1 bar Flow frequency: F1 = 8.1Q − 3                   F2 = 13Q − 6.5 (F is frequency in Hz, Q is flow rate in L/min)