Only heats water to 1oo degrees and temp on remote is set at 140 ?

There is no real proper temperature for a water heater. THe limiting factors are whether or not there are children in the home. IF there are, the temp is supposed to be set to 120 degrees F or less. IF you are concerned about germs etc and have no children then you can set it to 140 to 160.

Raising temperature above 120 degrees requires service call.
Or change dip switch settings and risk voiding warranty and causing service call expense.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html#temperature

Earliest versions of Rheem tankless 2006-8 let you set temperature up to 140 degrees F using remote.
However the hotter setting caused error codes because the burner cannot keep up with both high temperature and large volume of hot water rushing through pipe. Especially in winter with cooler incoming water that must be heated more to reach temperature set point.
The burner simply cannot keep up.
So Rheem changed maximum temperature at remote control to tepid 120 degrees, which is not hot enough for folks wanting hot shower, or folks filling whirlpool tub because water in tub cools before tub fills.

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

hold the up button until it flashes 140 then release it and while it is still flashing just punch the down button. this will set it for 140 degrees

You posted under water heater.
Open following link for adjusting water heater temperature on typical gas and electric water heaters:
State electric has ABC
White Rodgers gas thermostat has ABC
Honeywell gas valve has ABC
Each is shown on following link:
http://waterheatertimer.org/How-to-adjust-temperature-on-water-heater.html

60 degrees C is 140 degrees F.
You can get burned pretty quick at 140 F.
I suggest 125-130 F and see if that works
First aid for burns is to apply cool water immediately.

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.

if you dont have a remote controller, behind panel in upper right corner there should be a small plastic bag with probes in it...140, 160..just look at about 3 oclock and there should be a place to insert probe.

Remove cover plates from front of heater, usually four screws each.Seperate insulation enough to see and you will see the thermostat. It is factory pre set at 120 degrees and normally be adjusted to 140 degrees. Use a small blade screw driver to adjust settings. Ihope this helps you. Thanks

you shouldn't have to set your heater to 135. dishwashers have a built in heating element for just this purpose.

once you start going over 120 degrees on your water heater, you start creating scalding problems.
130 degree water can cause second degree burns in 30 seconds
140 degree water can cause second degree and even third degree burns in 6 seconds
150 degree water can cause third degree burns in 2 seconds.

be very careful !

I think some one mis informed you, the normal temp on any water heater from the factory is 120, it should not go above that for reasons of sevear burns, as far as it't smart part it's just a name, you will lose a couple of degrees just comming torm the tank to the faucets, the water heater will allways keep the temp in the tank at what ever it is set at, it doesn't have the brains or computer to know what time of day it is but when the cold water comes in to the tank it comes thru a dip tube that goes to aprox 1 inch from the bottom of the tank, if you take a long shower and do not have a energy efficant shower head you can use up to 5 gals, per min of hot water where an energy efficant one only uses 2.5 or less and still has the same pressure at the shower head, the temp in your water heater tries to stay at the setting it is at depending on how much is used at one time meaning washing machine, filling tub or dishwasher at the same time, it lets more cold in as the hot goes out and as you know it can only heat up so much at a time and the cold water is just going across the bottom of the tank, so the name is just that no diffrent then any other water heater unless you went to a tankless water heater.

i guess it is electric ,check bottom element reset button .remove bottom cover with power off look for a button on bottom thermostat or limit if find push it to reset ,,then set the thermostats , set top to desired temp and the bottom at least 10 degrees more ex. top 130 bottom 140 this might prevent problem reoccurring if this not problem bottom element could be burned out.replace ele