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Zoned System - 24V transformer or ZVC to wire a new smart thermostat?

6 years ago

Hi All,

My wife and I bought our house 3 years ago. It has two zones using Erie Zone Valves (I'll be adding one to make it three within a year or so) and is a Burnham Series 2 natural gas boiler. When we moved in, both zones used the old style mercury thermostats, with only two wires. Both zone valves are wired to an external 24v transformer that's mounted to my wall.

I have since pulled an 18/5 wire from my upper level thermostat down to my utility room, ready to go! I also bought the Ecobee3 thermostat, which I have on hand. At this point, I'm ready to try and connect the thermostat, however I have a few questions:

  1. Should I be using just a 24V transformer, or should I spend the extra money and get something like a Taco Zone Controller? I feel like this makes the wiring less of an engineering task and everything is rather simple. However, I don't know if my system can handle it. I have a separate hot water heater so I don't need priority or anything like that...
  2. If I stick with wiring it using the 24v transformer, I plan to upgrade the transformer to a newer honeywell thats 40va to make sure it can handle the load. I have no problem buying and replacing it. However, I am TOTALLY confused on how the thermostat is wired. My wiring is like a rats nest (granted all zip-tied at this point). Can anyone point me in the direction of a wiring diagram that could simplify this for me?

I have 4 wires, two black and two red. I know the two blacks are for the thermostat wiring and the reds are for the boiler wiring. Since I haven’t removed anything yet, I can make a wiring diagram and take pictures to get it back to where it was. I just am not clear on where the extra C-wire gets wired to. Do I just wire-nut it to the same lead that goes from the Zone Valve to the common side of the transformer and then pigtail those two to the transformer?

Any help is appreciated! Thank you!

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