Does fan run during defrost cycle?
Likewise, does condenser fan run in defrost mode?
It is normal for the outdoor fan to run while the outdoor unit compressor is running AND the system is in heating mode, not in defrost mode. When your heat pump is in heating the outdoor unit (compressor condenser) is extracting heat from (even chilly) outdoor air.
In respect to this, how long should heat pump stay in defrost mode?
A typical heat pump will go into defrost every 30, 60, or 90 minutes if the outdoor coil temperature stays below setpoint (~31° F). MacFarland's system goes into defrost mode only when necessary.
There are timers built in to the computer control of the unit that restrict how often defrosting can occur. Generally a unit must run for a minimum of around 35 minutes after starting up before completing its first defrost. From there defrosts should occur no more frequently than approximately every 35 minutes.