Why is a new pc board set to the same as the board that it replaces

SOURCE: not enough hot water

Makes you feel good to save some money right? Have a great day!

SOURCE: rheem 92 gal. no hot water. breaker not tripping.

Have you checked to make sure that the elements are good by checking the ohms. Be sure that the power is off and the wires are disconnected from elements and then also be sure to check the ohms across the tank to make sure there is not a dead short in the element reading through the tank. If both elements are good then I suggest replacing both thermos then they will both be new and should work for you . Thermos can be problematic when trying to test them sometimes they won't always give you correct readings. Make sure you have the breaker off whenever you mess with a waterheater, and make sure you install the thermos correctly with the right wires going where they should.

SOURCE: low pressure on hot water taps and showers

Many states building codes require a pressure regulator and expansion tank for hot water heater installation. Check the pressure regulator if you have one as this would only affect the hot water pressure. Adjust or replace. Rap the expansion tank like knocking hard on a door. Hollow sound is good. Dull thud means it needs to be replaced as it is filled with water.

SOURCE: warm water only

You can eliminate the shower control knob possibility by turning on your hot water anywhere else in the house. If you get hot water in other places, then it could be the knob causing it. A substantial lime buildup in the tank can also cause poor heat transfer from the elements to the water.

SOURCE: rheem tankless water heater error code C4 13??

check diaphrapm valve or micro/switch best of luck