The reset button has popped for the last 3 nights and I have reset it each morning. It doesn,t do this during the day when water is being used. Also the water is scalding hot with the temperature setting just above the hot mark.

there must have been a power interruption during fill or while there was a flow (Water will not flow when power returns)
1. Turn of all hot water fixtures. Next press the ON/OFF button on the temperature controller twice. Will reset the fault.
Hope this does it. Let me know please.
Happy New Year!

PDF]Tankless Electric (RTE) Troubleshooting - Rheem

www.rheem.com/docs/FetchDocument.aspx?ID=87d15e35-5adf-4e9f...
Tankless Electric (RTE) Troubleshooting. Technical Competence .... For four chamber units (RTE18 & 27) go to paragraph 4T. 9. Conduct OHMS resistance ...

Rheem RTE 27 Series ' Use and Care Manual

https://www.manualowl.com/m/Rheem/RTE-27-Series/Manual/296033
Rheem RTE 27 Series ' Use and Care Manual - Page 1. Use & Care Manual Electric Tankless With Installation Instructions for the Installer Water Heaters The ...

It still has to heat the water for demand. It will cycle even when there is no demand.

You flooded water heater wiring compartment with detergent, and the wires were shorting so you turned off power and cleaned detergent. Now water heater doesn't work.

1) The heat from shorting might have tripped ECO reset button.
Open top cover on water heater, and push in red reset ECO button.
http://waterheatertimer.org/images/Jly-022-thermostat2-175.jpg
Be sure to re-install insulation and cover.

Other steps:
2) Turn off power. Remove wire nuts. Cut off copper ends of wire, and re-strip each wire so fresh copper shows. Make sure no detergent is on the copper. Use new wire nuts and twist very tight against copper wire.
3) Cut back burned ground wire. Remove ground screw and clean thoroughly. And then reattach clean copper to ground screw.
4) Turn power back on.

5) If water heater still does not work, then test across top two screws on upper thermostat for correct voltage.
http://waterheatertimer.org/images/Jly-022-thermostat3-175.jpg
http://waterheatertimer.org/Test-electricity-to-water-heater.html

Add a comment for more help.

Take a moment and rate answer for accuracy:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

You posted under tank-type electric water heater.
1) Check the circuit breaker.
2) Open top cover located on side of tank and push in reset button.
3) If these two actions do not restore function, then open following link for complete troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-water-heater.html

There is a solution.
Ordinary tank-type electric water heaters are fully repairable by homeowner.

You have a new heater that works fine most of the time, but reset button trips.
That says tank is getting correct electricity.
It says that elements are good.
And you don't have sediment problem with new tank.

If you do not want to test parts, then replace upper and lower thermostats for $28.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html
The reason I suspect defective thermostat is that tank has 4 parts: 2 elements and 2 thermostats, and you have plenty of hot water so elements are probably good.
The reason I replace both thermostats is to avoid uncertainty.
Tighten screws very tight against copper wire.
Be sure to put back insulation and covers on water heater so thermostats not exposed to cool air which can lead to overheated water.
Then send bill for $28, plus labor and aggravation to Rheem
Your plumber should have done this for you as part of warranty, but sometimes self-sufficiency is valuable.

If you want to test water heater parts before replacing anything, then buy multimeter and take 30 minutes to become electric water heater expert:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html
Buy cheap multimeter at home center.
When testing continuity or testing elements, rotate multimeter dial to Ohms.
When testing for voltage,, rotate multimeter dial to 240-250-277 VAC

You can also double check anything fixya or plumber tells you by posting question on professional water heater forum like the Tank:
http://www.thetankatwaterheaterrescue.com/forums/forum3/

The problem I have encountered in this is the thermostat is going bad and tripping out. Inspect the ends of the elements and make sure ther eare no black ends on the wires showing elements may be shorting out causing thermostat to trip. More than likely change the thermostat out and you should be good to go.
They are not to exspensive and local hardware stores carry them.

My guess would be that the heater elements are coated very heavily with calcium deposits and are not oeperating effecient enough to keep up with use. These can be removed and replaced or cleaned but the tank itself would also be suffering the same problem. I have never tried decalcifying a tank because the age of water heaters are usually more energy and money saving to just replace. sorry

Teresa, the same exact thing happened to me this morning.... please let me know what you find out.... :o)

If you reset the water heater the first time you were without, Then odds are it is the water heater. probably an element went back. If the power off check for continuity.

Please rate this response and Good Luck, Phil