Code 14 comes up on the remote what does that mean

Before calling Rheem or service technician, open following link for troubleshoot resources including error codes, Rheem chat, typical required maintenance manual, and possible product manual:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf

Error codes are start point for troubleshoot.
Error 14 is 'overheat wrap fault.'
This can include venting problem, failed heat exchanger, bad safety circuit, gas problem.
Rheem does not have a service manual posted for this specific problem.

Additional information: Tankless water heaters consume large amounts of gas during combustion. The combustion burns away hydrogen and the remaining poisonous byproduct is vented into the atmosphere at each home day and night.
Byproduct includes acidic water vapor that condenses along the vent pipe and drips back down vent.
Each tankless vent pipe has a drain line that directs acidic water into household drain.
If this drain line becomes clogged, or if vent was not installed correctly, then water drips down into heat exchanger and can erode or crack exchanger.
The typical maintenance manual above shows steps that can solve many tankless problems before they happen.