What kind of “boot loop” you are in?
If you give me more detail a may give you some guidance….. anyhow to run an opensprinkler without a RTC is not advisable!
In theory NTC should provide right time syncronisation, but since the unit restart very often and syncronisation require more trials……
By the way , I will upload a new release of ESP8266 OpenSprinkler at the end of the week, it will include several improvements:
OTA upload capability to upload firmware by TCPIP
WiFi Manager to select WiFi SSID and password without USB connection
other minor and bug correction.