Rheem heat pump kicks on 410a unit comp & os fan run also inside fan. Vapor line gets hot and then comp shuts down os fan continues to run also inside fan. No warm air inside air just circulates? You can SD & repeat this in about 5 min but same results? Suspect something is protecting system from LP or HP ????? It ran in A/C ok a month ago?????

SOURCE: rheem power vent water heater shut down due to toxic vapour

Are you getting an error code? I could just be the pressure switch on the unit not allowing it to come on. You can try removing the hose from the inducer and blowing into and drawing air in and out of the tube. You will hear a clicking noise when you do this. Reattach the hose and try the system. Also, you have to unplug the unit for at least 10 minutes and then plug it back in to reset the controls. If the "Guardian" system still senses the fumes, it will not allow the unit to kick on. I could be awhile for the fumes to disapate before it will work. Try putting a low volume fan on the base of the unit to try and keep fresh air moving around the "Guardian" sensor.

SOURCE: 1 unit intermittently shuts off and other won't ignite

if you have the exhaust run together it will not light up,, they have to be seperate,, the computer board sences the unburnt gasses and will not allow it to start,,

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: richman gas lp tankless hot water heater. used for

I had the same problem with my Paloma a year and a half after installation...contacted Rheem\Paloma\Richman customer service (800-432-8373) and they recommened a local installer in my area. The technican diagnosed the problem as the "flow control valve"; he managed to get Rheem/Paloma to cover the part under warranty...I only had to shell out the money for the install.

SOURCE: Rheem Tankless wh model rtg-74pvn shuts off error code c4 76

Open following link for rheem tankless resources, includingerror codes and typical maintenance.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

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