We have a gas central heating & hot water system with a back boiler. The boiler is downstairs, the hot water tank is upstairs. There is a room thermostat and a cylinder thermostate. A three way valve (honeywell 4000-3916-003) is there along with a Siemens RWB9 programmer.
The problem is the central heating only comes on if the cylinder stat is calling AND I force the Honeywell valve open using the leaver on the side. As soon as the hot water tank reaches temperature, everything goes off.
The Siemens programmer says the CH should be on but it seems to be impossible to put it on by itself. As far as I can tell the room stat does nothing at all.
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