I just removed my old dial thermostat for my oil-burning furnace. There's a white wire and a red wire, but beyond that I can't tell what the wires are for. Neither the wires nor the old t-stat are labeled.
Also, how do I (safely) tell if my system is millivolt/24/120/240?
with just those 2 wires it is no different then a light switch being wired up.if you ever want to install a digital stat in the future you would need a 3rd wire to power it up..all your doing is closing the 24V control circuit for the boiler.