Hi. I have an open vented central heating system with a Glowworm Fuelsaver boiler, Drayton Flowshare 2 diverter valve and an ancient looking Randall 4033 timer. The problem is this: If I turn off the hot water at the timer or turn tank stat low then the heating works fine switching on and off correctly with the roomstat - no problem. If the heating is turned of or roomstat set low then the hot water works fine - being regulated by the tank stat. However with the heating and hot water on together ( stats not made temp yet ) the hot water stat seems to overide the heating stat with the diverter valve staying in the heating position ( no hot water being made at the tank so it stays cold ). This means that the heating stays on permanently even if the room stat is set to zero until the hot water stat is turned down or switched of at the timer. At this point the heating control is returned back to normal. So to put it simply if someone has a bath the heating goes into a permanent on condition until the hot water is manually switched off at the timer. Also to heat the hot water the room stat has to be turned to zero.
Apart from this the system works fine. We have had this problem since we moved in but I'm getting a bit tired of it now.
Hopefully this is just a wiring issue and someone can point me in the correct direction. Thank you for any help.