The new communicating, wireless, 2wire, 3wire and zoning systems do not allow the customers to shut off or put their thermostats and sensors into emergency heat during a power outage. The display on most of these models go blank during a power outage making the switch impossible until the power comes back on and it is too late! So, if you have one of these, you need to turn the breaker to the outdoor unit off. When power comes back on, you can switch the thermostat to emergency heat then reapply the power to the heat pump. After the recommended time by the manufacture has elapsed then you can turn your thermostat back to the auto mode.