iStop® is the winner of DESIGN PLUS AWARD powered by ISH


DESIGN PLUS AWARD powered by ISH competition rewards products that intelligently combine technology and design. A key role in the assessment was played by innovation, sustainability and energy efficiency.

iStop® for energy transition. Our antifreeze valve is the ideal solution for protecting domestic heat pump systems, especially in case of no electrical power. It has also been recommended by major heat pump manufacturers.

Europe has the ambition to create a zero-impact society from 2050. Many measures have been taken to make this transition a success. For example, many efforts are being made to make construction more sustainable: many owners assess their traditional boilers and replace them with heat pumps, also thanks to bonuses.

An overall assessment of individual situations helps better define how to structure a system and how to ensure that it is protected and will provide a long service life.

Currently, self-contained heat pumps are widely available on the Italian market. TThese are the ones with an external unit connected to the system through hydronic flow and return pipes. It is these systems that are subject to the risk of freezing. To prevent it, many installers opt for heating cables, but this solution is not optimal, especially where power failures are possible.

The antifreeze safety valve designed by Caleffi, on the other hand, is mechanical, so it works perfectly even without electricity.

The antifreeze valve is a mechanical protection system that can drain the water contained in the circuit. When the temperature of the water in the pipe drops below 3 °C, the obturator of the antifreeze valve opens and drains off the water (an automatic filling unit is essential). The obturator closes when the medium temperature returns to 4 °C.

The device must be installed vertically at the bottom of the pipes, leaving at least 15 cm clearance from the ground so that the block of ice that may form underneath cannot prevent the water from draining from the valve.

If antifreeze valves are used, the minimum set point for the cooling function must be at least 2 °C higher than the nominal drain temperature of the valve. Otherwise, the antifreeze valve may drain while the heat pump is operating in cooling mode.

To overcome this problem, the market offers types of antifreeze valves complete with air sensor for managing operation in the summer season. When the outside temperature is over 5 °C, the air temperature sensor prevents the antifreeze valve from operating. This prevents the valve from cutting in during operation in cooling mode during the summer.

Antifreeze valves 108 series