Rheem flame sensor
I have a Rheem Criterion II, Plus 2 furnace. It is barely a year old. The flame sensor needs to be cleaned every few days. The place I bought it it from says there is no cure for the flame sensor problem. Even if they installed a new one it would still have the same problem. Now they won't even come out when the thing won't fire up. The last tech who came out, showed me clean the sensor, but this is practically a new furnace. Are they correct in saying the problem can't be cured? Am I stuck with a POS? I thought Rheem was a quality product. Would another dealer work with me on this problem? I have to clean this thing every week, sometimes a couple of times a week. I'm afraid to go on an overnight trip, because the thing might not work and the water pipes might freeze. Can anyone give me a clue? i would have a piece of somebody at the hvac co. call rheem, file a complaint. sounds like you may have a bad ground Thanks for the reply, hvac4u. I have noticed the flame sensor moves a little when I clean it. Could this be the source of the bad ground? If not, where would I start looking? I'm gonna call a different dealer if I can't do a simple fix. This outfit did lose another sale, as I am gonna get a new cac unit, but it won't be from them. I've seen some pretty bad enviroments in rentals and I never have to clean a flame sensor weekly. This is not a common problem and it sounds like you may have an uneducated company working at your home. They don't give you a reason why this is a problem even a bs reason? What kind of enviroment is your furnace installed in? I own the house. The reason they give for the flame sensor needing cleaning is that during the combustion process a coating develops on the sensor which causes it not to function properly, and if it is replaced, the same thing will happen. The prior reply mentioned a bad ground. I think that is the problem, as the probe end of the sensor moves around when it is touched. It locked out again this morning, and instead of cleaning it, I jiggled it around and the furnace fired up again. I suspect the turbulence produced by the burner causes it to move as well. Is there a way to tighten it up, or will it need replacing? Definitely you should not have to clean it every few days. Once a year should be good enough. Can you see if the movement may cause the rod to move outside the flame. If this happens of course no flame will be sensed and the unit will not operate. Cleaning may just be moving it back into position. Also check that the leads from the sensor to the control board are tight. Fiddling with the sensor may be improving the worsening the connection resulting in the problem. I have a Criterion II furnace and it works fine - I just clean the sensor once a year. I did notice this morning that the thick wire looking probe can move to the very outer edge of where the flame forms. I moved it down to the middle of the flame path, and it fired up. I suspect the only cure is a new one, as the thing will most likely continue to move due to the flame turbulence. Is there only one screw holding it in? Is it moving due to a loose screw or is the sensor itself warped. If it is warped then you will probably need a new one. Can you not stop the movement by tightening the screw. I guess the unit should still be under warranty so I guess they should fix it. Maybe you should find another dealer given the advice these people have been giving you!! It's just the probe end that moves. The base is tight, as I stuck a nut driver on the screw to see. You don't buy the explanation about the combustion gases forming a coating on the probe? I believed it for awhile, but it kept on happening, and I knew that couldn't be right. Yes, I'm gonna try another dealer. Yep I don't buy that - if that were the case how come most furnaces work fine. There may be some truth in that but it will not happen so quickly. I guess the tech really has no answer to the problem so he tells you something so as to not look stupid. As far as I know the coating that affects flame sensing tends to be particle based such as dirt and dust. Gases can only form a coating if they react with the metal and I believe these sonsors are designed with stable metals to prevent this kind of thing. I really don't understand why people do this - if they don't have the answer they should say so rather than misleading other people. Good luck and hope you get it fixed this time. if the base is tight and the sensor moves it is broken, should be 5 yr warranty on that part. i would have a piece of that install company, they give the rest of us a bad name. where are you located? I'm located in Louisville, KY. I was surfing around the web, looking for info on flame sensors. This particular one has the 90 degree bend on the end. I noticed these seemed to be a pretty standard part, used by different brands. It got me to wondering if they are all the same? angle of sensor, length, and mounting....other than that they are the same. be sure mounting is proper position to put the sensor into the flame Basically the flame sensor is nothing more than a piece of metal that conducts electricity. It is made to withstand high temperatures since it has to sit inside the flame. Current is passed between the burner plates, through the flame and out to the sensor. This is how flame is sensed - by passing current through the flame. The criterion II uses flame rectification (conversion of an full wave AC to a half wave AC) to sense flame. The actual physics of the sensor and the burner plates form a diode. However, the actual shape as pointed out by hvac4u may be different depending on your furnace model so you need to get the extact replacement specified in the installation/service manual. You can buy these parts online and do the work yourself - it not difficult. However, you should be able to get it done under warranty for free. I replaced the flame sensor today. I went ahead and bought one, as it was only $8.00. So far so good, but time will tell if that fixed it. I could move the metal rod in the one I removed about 180 degrees in the porcelain/ceramic holder. I'm sure it isn't supposed to move, as the new one doesn't. I didn't break the holder open to see, but I was wondering if there was an actual ground from the sensor rod to the holder to the chassis of the furnace? I'm not sure that there is a ground involved in this. As far as I know the control board sends an AC current through the flame sensor, which then passes through the flame and returns to the control board. I believe the return path is through the burner so it may well be the ground. I will check the schematic when I have an opportunity in the future. I am thinking that you mean the connection from the sensor to the control board - yes it may well be that the connection was not good due to the movement and so it could not sense the flame. The sensor, flame and burner assembly act like a diode (you can think of it as a one way electrical valve). The control board then detects that current is not only being passed but that it is only one way and uses this info to say a flame is present. Hopefully you have fixed your problem. I am still puzzled by why it was broken in the first place - unless the install company broke it during installation. Who knows for sure how it was broken. Having had experience with assembly line operations, I know people will put defective parts in a unit. Whether they knew it was defective is the question. Sometimes it's obvious, sometimes it's not. It's possible it was only a little loose, and all of the cleaning I was doing eventually finished the job. I'll just have to wait and see if this fixed it. I hope so.
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