Vaillant VRC 400 - 20010843 - DISCONTINUED Weather compensation can offer fuel saving benefits by taking into account the outside temperature and reducing the boiler heat output accordingly. The VRC 400 has a flexible 7 day or 24 hour time control with independent time control for heating and hot water. When used with ecoTEC combination boilers, the hot water program can be used to provide time control of the 'AquaComfort' system. When used with ecoTEC combination boilers, the hot water program can be used to provide time control of the 'AquaComfort' system. When used with a system or open vent boiler and additional VR 65 Control centre the VRC 400 hot water channel can be used to time the hot water cylinder charging. The programmer has 3 independent on/off periods per day, central heating advance function, holiday set-back function, adjustable set-back temperature and 3 room temperature profiles. There is also a calendar function for automatic summer/winter changeover. The VRC 400 can be used with all ecoTEC boilers.