Arrived on site for a report of no heat on the first floor and in the living room, along with a loud chattering noise coming from the zone control board. Inspection showed the control board was experiencing fluctuating power. Whenever any of the Nest thermostats called for heat, zones 3 and 4 would intermittently lose their call, which was consistent and repeatable. After extensive wire tracing, I identified all zone valves, zone separations, thermostat locations, and their corresponding zones. Based on system behavior and testing, my current hypothesis is that the system is experiencing an intermittent zone control board failure, compounded by three Nest thermostats operating on two-wire configurations. These thermostats appear to be drawing excessive power, causing voltage instability and disrupting calls from other zones. Further diagnostics and discussion of a long-term solution will be required, and a return visit is necessary. At this time, I confirmed proper operation of the f