I have a question regarding 'emergency heat' with respect to HVAC systems. I had a new Unico system installed with an American Standard 15 SEER compressor and an electric duct heater. The duct heater has separate electric elements (three stages) We had a cold nght the other night, about 12 degrees, and woke up in the morning with the house a cool 54 degrees.
After talking to the installer - he informed me that I need to switch the unit to 'emergency heat' in order to maintain the house internal temperature during very cold nights. They also informed me that the supplemental heat does NOT run when the heat pump is running and will not automatically switch to a second stage electrical heat when the heat pump can't keep up.
I had thought that the heating cycle would be a multi range cycle:
1) heat pump only
2) heat pump & 1st stage electric
3) heat pump & 2nd stage electric
4) emergency heat (in the event of a heat pump failure of some sort)
Is this correct or should the duct heater only run when manually switched 'on'? Also - what would be the lowest outside air temp that I can expect the heat pump to generate heat? I have heard as high as 28F to as low as 6F.