went to a job today , heating not working , anyway fault was found as a faulty programer, but anyway, it was a solid fues system with gravity hot water and pumped heating with a indirect cylinder, the cylinder was piped up in 28mm and heating in 22, there were 2 stats on the gravity , one high limit on the hw flow set to 80oc and low limit on the hw ret set at 40 oc , cananybody tell me excactly what these do , there was also a room stat but no cylinder stat, and no motorised valves, there was an electrician on site, but he didnt know how it worked.............!!! also has anybody got a decent wiring diaram fo one of these?? thanks guys as always!!!