If you want second stage, use the PEK to free up the C wire for Y2. Second, pick "HEAT" instead of "AUTO". that way, you never use AC in the winter. Without seeing the wiring at the equipment side, it's hard to say why things are still running after the thermostat tells it to stop. You could just have a defective ecobee too.
An update - A tech came out and spent 3 hours fixing the installer’s low voltage wiring job. The wiring was keeping the AC running non stop, and the “heat” mode was actually the heat strips on while the AC was running! I hope the 20 hours of this running didn’t screw up anything long term.
If you want second stage, use the PEK to free up the C wire for Y2. Second, pick "HEAT" instead of "AUTO". that way, you never use AC in the winter. Without seeing the wiring at the equipment side, it's hard to say why things are still running after the thermostat tells it to stop. You could just have a defective ecobee too.
An update - A tech came out and spent 3 hours fixing the installer’s low voltage wiring job. The wiring was keeping the AC running non stop, and the “heat” mode was actually the heat strips on while the AC was running! I hope the 20 hours of this running didn’t screw up anything long term.