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I recently purchased a home with 4 zones of hot water baseboard heating connected to 4 different Taco zone valves. I am not too familiar with the wiring for these zone valves as I have been spoiled in the past with the combined forced hot air/AC units. The NEST thermostats worked fine for about a month but now they all enter low power mode for about 8 hours each day to recharge. I am trying to determine the best approach to fixing the problem. Here is what I am working with
Zone 1: 2 wire from Taco/4 wire from AC handler
Zone 2: 2 wire from Taco/4 wire from AC handler
Zone 3: 2 wire from Taco
Zone 4: 2 wire from Taco
Is it possible that 4 thermostats is too much for the same 24V transformer?
Based on Google searches, it appears that I can add a common wire from the air handler for zones 1&2. Will the thermostat use the power from the common while the thermostat is in heating mode? Will it stop drawing power from the 2 wire?
Final question: Will my 2 wire zones draw power while the heating system is not in use during the summer? I am not sure when the Nests draw power to charge.