I am trying to sort a heating problem for a freind and I suspect that there may be a wiring problem. Her setup is as follows: Flow from boiler to cylinder cupboard then in to pump. From pump to a 22mm T, one side of the T goes to the cylinder heating coil other side of the T goes to heating flow but via a zone valve. Most of the diagrams I have seen have either a 3 port valve of 2 zone valves so I'm a but stuck and I don't know which wiring diagram to refer to. She also has a cylinder stat and room stat. Also what position do zone valves default to? I'm assuming that when power is removed they close, is this correct? Thanks chaps.