I have a vacation home with 2 zone heating. In the winter, it would be nice to be able to have remote access to the thermostat and 'turn on the heat'. Normally when vacant the 2 zones will be set to 52 degrees and it is 2 wire. I was thinking of installing a 3rd thermostat wire (with C wire) and one of the new thermostat ecobee/nest/etc that I could access remotely.
However, is there a way to wire this to essentially 'override' the 2 existing (manual) thermostats so that when we get there we can manually use the 2 zones separately. I'm just trying to avoid an additional $250 and the next to impossible addition of a C wire to the existing thermostats.