I have a Vaillant 824/624 turbo max, problem is when the ch on and i run hot water this disconects the ch but hot watrr stays on ie the hot water light still flashes. The only way to reactivate ch on, is to unplug the wires. Ie you want hot water reconect the wire ch unplug wire. I had a new mb fitted a water sensor fitted a new control panel to no avail. Considering a new boiler, unless some1 can give any hint to what problem could b. Thanx