I live in NJ.  I have a geothermal heat/ac unit with no conventional heat backup.

FHP model SX048-1, Pump HR003-1XXX-XXX

intermittent lockout problem, usually only occurred when large differntial between thermostat temp and house temp, only with heat

this solution typically worked:  pull thermostat remove battery to clear memory, reset breaker and reinstall battery and reinstall thermostat

system takes 10-15min to reset then works, has happened a couple times this summer, there is a specific sequence to resetting thermostat and breaker and I always forget and usually just try multiple methods, i.e., reset therm first, or turn breaker off, etc.

The breaker is never actually tripped

This is not working today,

any ideas

Is your filter clean and the condensate pan draining ok?
joe