The existing Ecobee set up employs the PEK because I do think there are only four or 5 wires going from the thermostat into the furnace but I am able to relatively very easily include much more wires if required to get two stages (thermostat is sort of right previously https://copyright-dosage81111.bloguetechno.com/copyright-side-effects-things-to-know-before-you-buy-70870021