Have just got this unit but my original unit (honeywell CM67) only has two wires coming from the combi boiler (Alpha CB50). By the diagram the BDR91 requires a 230V supply & my original wires should go to terminal A & B. I have two questions:1. can the 230V come from a seperate fused spur & 2. Do my original two wires go in either terminal A & B?