We have to reset daily A-7 - Bosch AquaStar 2400ES-NG

Before calling service technician, open following link for troubleshooting resources including error codes, manual, links to bosch, phone number, :
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

A7 is outlet temperature sensor fault.
Temperature below freezing or above 210 degrees F

1) Check red wire connections at hot water temperature sensor. Clean terminals with an eraser. If badly corroded, replace sensor and wire harness. (See Fig. 63, page 46 in manual).
2) Sensor may trip if water temperature drops below freezing to protect heater from freezing conditions. Any damage due to freezing conditions is not covered under warranty.
3) Clean inlet filter screen and clear any debris out of shower heads, faucet aerators and whole house filters.
4) In areas where water has a high mineral content, periodic descaling may be necessary.