No hot water

possible bad power transformer or unit is overheating

PDF]Operation and Installation Manual Outdoor Tankless Water ...

https://www.rinnai.us/.../U287-1932(00)_Outdoor_...

Rinnai America Corp.Temperature controlled continuous flow gas hot water system. .... This water heaterwill attempt to provide hot water at the temperature setting even when the ...

Hot water system temperatures and the code ' Plumbing ...

plumbingengineer.com/content/hot-water-system-temperatures-and-code

Feb 1, 2015 - There have also been incidents where the circulating pump stopped ...before it connects back to the cold water inlet to the water heater. .... Is there a maximum temperature limit for domestic water heaters? ... a means to limit the maximum setting at the valve to 120°F (49°C) or ... Some do and some don't.

[PDF]User's Operation Manual - contents - Navien

You might have crossover problem caused by bad faucet cartridge.
http://waterheatertimer.org/Crossover.html

The green standby light should come on when 240Volt power is applied. Page 6 manual.
Both red lights should come on when tankless is activated. Page 6 manual

RTE 13 requires 60 amp breaker and 6 gauge wire
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html
http://waterheatertimer.org/pdf/Rheem-TanklessElectricUC_AP15447.pdf

Factory temperature setting is usually default 120 degrees.
Adjust temps page 11 manual
Thermostat calibration is always approximate.
120 degrees is not hot enough to burn the skin.
Exceptionally cold incoming water temperature can cause tankless not to heat enough hot water: install tempering tank to preheat water to room temperature.
Tankless cannot be exposed to more than 11 grains hardness in water. Delime tankless yearly, clean water filter monthly, do not install low-flow restrictions or conserve water since the flow rate must remain high for tankless to activate.
Rheem does not post service manuals for their tankless water heaters.
Call Rheem 800 432-8373

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

The manual says:
http://www.coinwash.com/temp/rinnai.pdf

"For the name of the Authorized Distributor or Installer nearest you, please contact your local HVAC dealer or gas service technician, visit the Rinnai website (www.rinnai.us), call Rinnai at1-800-621-9419 or write to Rinnai, 103 International Drive, Peachtree City, Georgia 30269"

Manual says that the remote is for setting temperature.
When you turn on hot water spigot, tankless water heater will heat the water to the set point temperature.
If water heater is not set up to use remote, then tankless unit will heat to 140 degrees F.
"With the MCC-45-4US remote control installed the water temperature is adjustable from 96
to 180°F. The water temperature cannot be set to a temperature other than 140°F
without the use of the MCC-45-4US remote control unit. If you require a temperature
other than 140°F you must install the MCC-45-4US remote control unit."

"Error messages are displayed on the remote control units, simplifying service calls."

Page 9 of manual shows hot to set temperature using remote.
Water taps must be shut off to set temperature.
Circulating pump must be turned off.
"Simply press the H or C button until desired temperature is displayed"
"green in-use indicator will display"

If your unit is not working, the manual says to contact local plumber.
Fixya has specialists who will talk to you by phone about your problem for a fee.

check to see if you have a blocked line on the hot water side

Power outage will reset Rinnai unit to that temperature. Read manual for more info.

check the error codes on it by pressing the on off button for 2 seconds then while holding the on/off button press the up button this should display the last 9 error codes let me know what they are

Its A Possibility The Left Over Water In The Hot Is Frozen. If Your Line Is Exposed Outside Somewhere It Can Easily Freeze Up. Turn On The Hot Water Everywhere In The House And If Accessible Check The Lines To See Where The Warmth Ends. You Can Leave One Off Over Night In Hopes That It Will Eventually Defrost.