I currently heat with an outdoor wood boiler. This maintains the water temp going through my WM-ultra at about 180°. The heating limit on the ultra is set to 150° as a backup if the fire goes out. At this setting, when the house calls for heat, the boiler does not fire. The readout says that the system is satisfied. When the hot water tank calls for heat, the boiler fires and maintains 190°. I have the setting on the DHW at 140°. Any idea why its firing to 190° when I have it set for 140°?