I have a Danfoss CP16 controller. Even with heating and hot water both off, and no red lights showing, the boiler is still firing and the radiators getting hot. I presume this is down to a faulty controller as, looking at the wiring diagram, the power to fire the boiler comes from the controller via one or other of the zone valves?
No, the fault is not with the controller. You have a fault with one of the zone valves. The boiler and pump are switched by the valves, the controller only operates the valves via the stats, it does not control the boiler.
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