ESR 125A Changeover Switch (ECO125) Product Information Change from mains to generator power easily during a storm with this 125 amp changeover switch. Built to work safely in your home, this is for DIN rail mounting in an enclosure with at least 4 empty single pole modules. This two position switch has two normally open contacts and a pair of normally closed contacts. It is compliant with UK Amendment 3. ESR 125 amp 240 volt changeover switch. Suitable for switching between mains power and generator supply. 2 Position switch. Din rail mounting, can be mounted in a consumer unit or separate enclosure.