The Remote Outdoor Air Temperature Sensor for e-Series heat pumps is required when the heat pump
intake air is ducted from a remote location, such as when the heat pump is installed in a mechanical room but is fully ducted to the outdoors.

It is also recommended in applications where the air temperature at the intake of the heat pump deviates from overall ambient conditions when the heat pump is off. This could be due to hot or cold air from other intermittent sources, local solar gain, etc.