The OPTIMA PLUS has two pumps: a powerful submersible pump in the storage tank and a centrifugal pump in the rainwater unit. Depending on the operating mode, only one of these pumps is in operation at any given time. In "rainwater mode", the submersible pump in the storage tank pumps up to 60 litres of water per minute to the extraction points. In this mode, the pump in the rainwater unit is out of operation and no pump noise can be heard in the house. The submersible unit is powerful enough to pump water through long supply lines of more than 25 m in length between the storage tank and rainwater unit. It is only in top-up mode that the submersible pump in the storage tank is shut down and the centrifugal pump in the wall-mounted rainwater unit starts up to keep the rainwater circuit supplied with water.
If the rainwater in the storage tank runs out during a prolonged dry spell, the system switches automatically to mains water operation. The low water level in the rainwater tank is sensed by the float switch. The rainwater units can also be switched manually to mains water operation at any time. A small top-up tank in the rainwater unit ensures an uninterrupted supply of water from the rainwater circuit.
The control systems of many makes of rainwater unit consume up to 15 watts in standby mode, by day and by night, 365 days of the year. This standby power consumption accounts for a large share of the energy required to operate a rainwater harvesting system. To solve this problem, WISY partnered up with the Mittelhessen University of Applied Sciences to develop the highly efficient ZETA 02 pump controller. This innovative device has reduced standby consumption to below 0.2 watts, a small revolution in its own way. Compared to conventional rainwater units, the ZETA 02 uses 97 % less energy in standby mode. The ZETA 02 is a standard component in all WISY rainwater units.