A zone heat problem was not letting the gas boiler work efficiently. This is an older home with an upgraded system, It was determined that there were TWO issues; a failed [open] circuit on one zone and a failed [ancient] thermostat on the other. Although either ONE problem was a simple fix, TWO SIMULTANEOUS problems made the fix more complicated. The Milani tech hunkered down and, using some logic, sorted out the issue within 20 minutes, installed the needed thermostat and recommended a thorough look at the ancient wiring on another visit. The system is now operating normally !!