I have never set a 4 digit security pin on this thermostat and all thermostat functions are presently accessible. I may want to set a security pin number but noted that the factory default digits are 0000. If I set a pin number (say 1234), then at a later date decide to eliminate a security pin number, will returning the pin number to 0000 eliminate the requirement for a pin number or will the new required pin number then be 0000? The manual does not address this question. Thank you.