Navien NR-240A Gas pressure sensor replacement

Discussion in 'Water Heaters and Softeners' started by havasu, Feb 17, 2012.

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  1. Feb 17, 2012 #1

    havasu

    havasu

    havasu

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    My T/W/H is about two years old, and suddenly began receiving fault code # E 35, indicating irregular gas pressure. I called the tech. folks and they asked for me to confirm with a manometer that my pressure was perfect for the unit, and I determined it was. I again called the great folks at Navien, and they said it was most likely a faulty gas sensor. They asked for my address, and two days later I had a replacement sent to me via UPS.

    This is a write up to show the steps necessary to replace this sensor.

    Here is the tankless water heater in question.

    Water heater repair (14).jpg
     
    Last edited: Feb 17, 2012
  2. Feb 17, 2012 #2

    havasu

    havasu

    havasu

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    Remove the 4 small screws in order to remove the cover.

    Water heater repair (12).jpg
     
  3. Feb 17, 2012 #3

    havasu

    havasu

    havasu

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    This is the new sensor layed out with a few pieces of pipe, to correctly repair the incoming gas line.

    Water heater repair (2).jpg
     
  4. Feb 17, 2012 #4

    havasu

    havasu

    havasu

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    Here is the bugger in question.

    Water heater repair (3).jpg
     
  5. Feb 17, 2012 #5

    havasu

    havasu

    havasu

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    Remove the screw at the base of the unit, with the red arrow, in order to pivot the control panel out of the way. Since I failed to tell you previously, unplug the unit and shut down the gas for everyone's safety.

    water heater edit.jpg
     
  6. Feb 17, 2012 #6

    havasu

    havasu

    havasu

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    Using a long screwdriver and a long nose set of needle nose pliers, remove the two hoses from the sensor and unscrew the old sensor brackets.

    Water heater repair (7).jpg
     
    Last edited: Feb 17, 2012
  7. Feb 17, 2012 #7

    havasu

    havasu

    havasu

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    Pull the old sensor and unplug the wiring which leads from the sensor to the control panel. You will need to snip off a few wire ties in order to completely remove the wiring.And yes, I received a boo-boo to my thumb in the process!

    Water heater repair (8).jpg
     
  8. Feb 17, 2012 #8

    havasu

    havasu

    havasu

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    Feed the wires through the back of the control panel, making sure to follow the same path as when you removed the old wires. Screw in the new unit, making sure that the hoses are reconnected correctly, and zip tie the wires together to avoid burning and shorting the wires by accidentally touching the heated areas of the unit.

    Water heater repair (9).jpg
     
  9. Feb 17, 2012 #9

    havasu

    havasu

    havasu

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    Replace the bottom screw to the control panel, and give one final inspection to make sure all hoses are connected and wires are all tucked in. Place the heater cover back on and screw back in the four screws to keep the cover in place. It also helps to blow any dust from the inside, wipe down and dirt or debris from inside, and give a final coat of wax to make the water heater look prettier!

    That is it! Plug it back in, turn on the gas, and she should be good for a long time!

    Water heater repair (13).jpg
     
  10. Feb 17, 2012 #10

    LiQuId

    LiQuId

    LiQuId

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    ahhh the pressure switch was the culprit... I wasnt sure exactlly what you were meaning by "sensor" these do foul on occasion.
     
  11. Feb 17, 2012 #11

    havasu

    havasu

    havasu

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    The gas company said that is usually the first part to wear out. The company techs I spoke to didn't tell me how often this occurs, but I got the impression it does happen occasionally.
     
  12. Feb 18, 2012 #12

    LiQuId

    LiQuId

    LiQuId

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    yeah, i've changed out a few on boilers this year, you can test them by blowing on the tube ( or sucking depending on the switch type ) and seeing if the boiler then fires.
     
  13. Nov 24, 2018 #13

    Scott Lyins

    Scott Lyins

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    So where is the pressure switch located? You describe the pressure sensor but not the switch,,, thank you
     

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