It's that time of the year - old and the heating is playing up!
We have Danfoss FP715 CH controller. The boiler is gas and it's a separate boiler with the hot cylinder in the airing cupboard.
No problems at all with the hot water. Set the water on on the controller and we get hot water. Set the CH on on the controller and we get cold radiators! Have CH on and water on on the controller and we get warm radiators.
So basically the central heating doesn't work without the hot water being on. The boiler doesn't fire and the pump doesn't seem to come on either. I have a suspicion that when the hot water is on and CH on together that the heating isn't as efficient as it used to be (though that may just be my imagination). The whole installation is just over two years old.