Hi, My Vaillant heat pump system is timed to come on during the night, it normally comes on as planned and I wake up with a warm house, this morning the house was cold and my water was not heated. It was -3 outside last night, this is the second time this has happened over the last few months. The unit is reporting no fault, do I need to reset something, also my frost protect delay is 4 hours, I’m not even sure what a frost protect delay is, thanks for any help, Ady