Control 4 Thermostats draining batteries

BJonesNYC1

I have a radiant heating system. 4 zones. Heat only HVAC.
A Taco controller tied to a Triangle Tube HE Prestige Condensing boiler.
Zones are; 0= Wall mounted radiators for cellar/basement
1= Radiant manifold for 1st Floor- split into three separate thermostat controlled sectors (front/middle/rear)
2= Radiant manifold for 2nd floor-split into three separate thermostat controlled sectors (front/middle/rear)
3= Radiant manifold for 3rd floor- split into three separate thermostat controlled sectors (front/middle/rear)
There is a temperature sensor in each of those sectors that feeds data to the nine (9) thermostats that control the front/middle and rear on each floor. No problem for 8+ years. This heating season the 2nd zone has been faulty. It started with not supplying sufficient HW to the rear sector, and that thermostat constantly dying. Replaced thermostat. Repeatedly replaced battery. No change. No ALL three thermostats are failing. I replace the batteries and the system works perfectly. But then the new batteries are drained within a day and the zone fails again. I obviously have a short or some sort of electrical issue in that zone. But I have checking checked and reversed the polarity of the sensor wiring to the thermostat several times. No other wiring has changed so I cant imagine why I would get a short anywhere else. No other zones have problems.
The thermostats are Control 4. Tied to a whole house system so that I can monitor/change from smartphone. Have had four visits from my HVAC company. inexperienced/young technicians. Thoughts????

BJonesNYC1

HVACNUT

Check the transformer powering those thermostats. 

Jamie Hall

And if that doesn't work, you're going to have an interesting time finding the power drain.

The first and perhaps only rule is -- assume nothing. Imagine nothing. I'd start out by isolating any wires and wire pairs at both ends (labels, please) and checking for shorts between wires and to ground. Any wire with less than a megohm minimum between it and any other wire or ground is shorted and needs to be replaced, regardless of what else is found. Do the same thing for any connectors (Molex plugs are often bad actors, but any connector can be bad). Next step is a bit painful but may be necessary -- arrange each thermostat so you can measure the current on each wire. There may be a small current on the power feed and common return, if these are powered by a transformer -- but it must be the same on both for a given thermostat, and very very close to exactly the same on feed and return when the thermostat isn't calling. There should be no current at all on any controlled wire.

That should do for starters...

HomerJSmith

Could it be a bad thermo actuator? But a thermo actuator should run off of a transformer. Try disconnecting one at a time and check the results. Disconnect it at the control.

Try moving the switch (enable/disable) several times, it may be not making good contact.

mattmia2

How old are the thermostats? Perhaps the power supplies that make the power to run the tstat off of the 24vac are failing and forcing the thermostat to run off the battery.