Vent-Axia 563552 Ambient Response Humidity Sensor. Vent-Axia Has Been The Leading Manufacturer For 75 Years When It Comes To Ventilation. With This Experience Behind Them, It's No Surprise That They Are Innovators As Well, Continuously Producing New Lines With Energy Saving, Lo-Carbon Products. With A Vast Range Spanning Cool Air To Electric Heating, And Everything In Between, You Know Vent-Axia Is A Name You Can Trust With Your Ventilation Needs. The Va 563552 Is An Ambient Response Humidity Sensor, Which Is Designed Specifically For The Lo-Carbon Product Range. Featuring A Pullcord Override And A Neon Indicator, This Self-Programming, Electronic And Wall-Mounting Humidity Sensor Reacts To Any Rapid Increase In Humidity And Temperature By Switching A Vent-Axia Fan ‘On’. This Helps To Reduce Moisture Laden Air In Kitchens And Bathrooms And Restore A Fresh And Healthy Environment. The Sensor Is Convenient And Intelligent, With A Night Time Rh Increment Setback Feature, Which Suppresses Nuisance Tripping When The Humidity Level Gradually Rises As The Temperature Falls. A Changeover Relay Switch Is Also Included For This Sensor, Which Has An Operating Range Of 30% - 90% Rh. Dimensions: 87 X 87 X 33mm (H X W X D)