Review on Rheem SP20172 Flammable Vapor FV Sensor Kit in White - Compact & Reliable Solution (6.7X2.7X9.4 inches) by Jay Chowdhury

When I ordered this I was concerned it would not be an exact replacement as the back of mine had '25v' stamped on it but the online Description in this paragraph says nothing. I decided to take a risk as the painting looked exactly the same. When it arrived I found that the back of the sensor had '25V' stamped on it, although the description didn't mention this. Replacing an old one is very simple: disconnect the water heater from all electrical connections, remove the metal plate protecting the burner assembly, and climb inside by pushing the plastic housing surrounding the sensor outwards so that it pops out the hole in the water comes heater housing near the ground. With the sensor removed from the heater, remove the two plugs from the terminals of the old one and plug them into the terminals of the new one, then plug them back in. The controller will likely need to be reset before the new one will work. In my case, the reset process consisted of turning the thermostat knob up and down from low to high and back about 9 times after reconnecting power to the water heater. The reset method may vary depending on the brand of controller. These sensors work by changing their resistance when exposed to flammable fumes and other substances such as cleaning agents used near the sensor. If the resistance is outside the specified range, the control unit will detect this and prevent the water heater from flaring up. When the sensor is replaced with a new one, the resistance will be back in the correct range and the water heater will turn on. My water heater (Rheem Richmond) requires a resistance of 15 to 40 kΩ. I checked the "burned out" sensor before ordering and it read around 100k ohms, way out of range. A new one costs about 22,000. AN IMPORTANT CAUTION: Here are links from other buyers to workarounds to get the water heater running until a new part is obtained, which involves making connections on either side of a cereal bowl filled with water (which has a resistance of around 30K). ) or actually put a resistor between the terminals to simulate the operation of the sensor. Both should actually work, but if the true cause of the old sensor's failure was the presence of combustible fumes, then restarting the water heater could obviously be disastrous. The same applies to replacing a bad sensor with a good one. Do not turn the water heater back on until you are absolutely sure there are no flammable vapors nearby.