I NEED THE OWNERS MANUAL FOR RHEEM RTG-74XN-2 TANKLESS WATER HEATER

SOURCE: Rheem tankless rtg 74pvn - heater hot water shuts

This is something you will have to contact rheem about due to the fact you don't have a fault code

SOURCE: Tankless Hot Water Heater Rtg-74pvp-2 7.4 Gpm: hi i have a rheem tankless water heater, with flas...

Sounds like you may have the wrong type gas going to this? Is this an LP gas or natural gas unit? will say on label. Natural gas units run only on natural gas ditto for LP. Could be issue with manifold pressure settings. Could be obstruction in exchanger or vent. Have a authorized technician check over

SOURCE: We have enjoyed a Rheem Thermostat and a Paloma

Before calling service technician, open following links for Rheem troubleshooting resources, including generic error codes and contact information for Rheem and recent manuals:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://www.fixya.com/tags/rtg_74pvn

Error codes are start place for troubleshoot, and multiple error codes can indicate bad PC board.
Same error code on one machine can be different cause and solution than another machine.

Error 76 is usually communication problem with remote control.
Disconnect wires from machine, and clean terminals is a start point.
Wire between machine and remote might be bad, or remote control is bad, or PC board or wiring connections are bad.

The problem might be solved by having technician catch the machine up on yearly maintenance.

Manual for same-similar product shows maintenance and troubleshooting and a few error codes, but not 76:
For the most part, the manual recommends calling service technician instead of offering DIY details.
http://waterheatertimer.org/pdf/DirectVentManualRTG-74PVN-1.pdf

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