While you wait for answers, we may have found some information which could help you.
Click here for Light Work Upstairswiring horstmann centaurstat 7?
Horstmann Economy 7 problem?
Whats wrong with my Vokera Mynute EHE boiler?
horstmann economy 7 heaters not coming on?
horstmann ChannelPlus H37XL?
Horstmann channelplus model H37 - ch won't come on?