Have a Richmond tankless water heater. How do you know if it's in bypass. And how do you get it out if it is.

SOURCE: water heater not heating it's a richmond water heater

Now change the thermostats........this is the only other thing it could possibly be.

SOURCE: Paloma PTG 74PVN Tankless Water Heater

did you check the filters on the the water valves, i am not exactly sure about your codes that are shoeing but if you could read it and post them, i know on some of the units 76 means there is low water pressure and the filters are behind 2 caps one on each side above the shut off valve take off the caps and remove the screens, clean them and replace them ,, make sure you turn off the water on both side first or you will get wet

SOURCE: Paloma tankless, gas, water heater, error code C7 76

If you look on the left hand side of the burner control module you'll see 4 capacitors - the capacitors have most likely failed...pretty sure anything code 76 is P/S failure. It may also be covered for manufactures defects. If the cap is blown..the top will be slightly raised as apposed to flat like the other nearby caps - they are called top blow capacitors...the damage should be evident.

SOURCE: power vent tankless heater has a down draft

I HAD THE SAME PROBLEM ON 2 OF THESE. I CALLED THE COMPANY AND THEY SENT ME A COMPLETE NEW VENT KIT WITH A DAMPER AT THE OUTSIDE WALL. HAVE HAD NO TROUBLE SINCE INSTALLING

SOURCE: rheem gas tankless water heater with error code c4 13

problem is inside burner compartment o2 sensor dirty or block..need to have a qualify technician clean it.