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I want to ask HVAC experts how to troubleshoot my floor heating system. I have a Lynx-85a boiler, pumping hot water into three zones, one per room and three zone valves. For some reason, original builder installed four thermostats. There is a main thermostat in front of the boiler room. It controls cental air conditioner that has no zones.

I tried to replace living room thermostat and it only has ~2V. Yet, it works just fine. It has two AA batteries and seems to be able to control zone valve. The other two room thermostats and main one have ~24V. I am confused about how the system is set up.

help grealy appreciated.

i took a picture of my zone valves and a page from lynx manual. i am not certain how it is setup.

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  • If the thermostat uses 2 wires, connect to R and W. A third wire C is usually needed for digital stats. Voltage is checked between R and W or between R and C. Look for 24v a.c. when the stat is off. Your diagram shows 2-wire stats. A 3-wire setup would include a C wire from the bottom of the transformer winding. The cool stat would also include a Y wire for cooling call. – John Canon Dec 30 '18 at 5:12

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