St-2e

[Kvothee531]

Hi, I just moved into a new ( to me) home that was built back in '06. It has the st-2e board there are 2 thermostats on the second floor, one wired as a master (rwygob) and one with just the three wires. On the main floor there is another thermostat wired as a master. In the basement (finished) there is another wired as a slave. I have no idea how this zoning makes sense. There are two ac/air units outside, obviously no heat pump (oil heat and central air). I was planning to upgrade the board so I can start using smart thermostats but I don't want to have to rewire the house. Any ideas?

[Steven W.]

You will need to replace your ST-2E zone board with the NCM-3z. NO new wiring if you are not putting a WIFI stat on the 2nd zone. If you are planning on putting a WIFI stat on zone 2 then "Yes" you will need to run more then 3 wires to that zone.