Our Honeywell ST9400C seemed to be working perfectly well until a few days ago when we tried to put the water on for an extra hour. I tried pressing the "Extra Hour" button on the left hand side of the front console and the display came up "Not Valid" and the same with the Override switch too. I tried the heating side too and it's the same.
Can't find anything in the instructions but don't understand why it's been working fine and then suddenly we don't have any hot water? The heating works but no hot water!
Is this a problem with the system or something else?
Can't find anything in the instructions but don't understand why it's been working fine and then suddenly we don't have any hot water? The heating works but no hot water!
Is this a problem with the system or something else?
