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Help diagnose intermittent buzz inside boiler cabinet and failure to fire

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This morning I heard an intermittent buzzing noise coming from inside my Peerless 63 06 steam boiler, single pipe, parallel flow. The buzz was not continuous. It was on/off/on/off/on/off, as if there were a buzzer controlled by a doorbell button that somebody was pressing in a steady, regular rhythm. The duration of each buzz is about a half second, followed by a half second with no sound at all, followed by another half second buzz, then half second silence, on and on and on. The on/off/on/off buzzing was going on for quite some time and the boiler was not firing. Just the on/off buzzing and no flame ignition. I should mention that my automatic damper was in the open position while the buzzing was going on, so I think I can rule out the automatic damper.

The only reason I became aware of the buzz was that I had gone to the basement to see why the temperature in the house had dropped from the constantly set 69 degree temperature (no setbacks in my house, ever) down to 64. All my radiators were cold. My mains were cold. The boiler was just a touch warmer than room temperature. The thermostat upstairs was blinking its call for heat symbol, and the buzzing sound was going on. My ears are terrible from too much age and rock and roll, so it was difficult to tell if the buzz was from the gas valve or from a relay or a transformer. My boiler is only about 10 or 12 years old. Six years ago when I bought the house, bought Dan's books and became a daily reader of this forum, I installed more Big Mouth vents than I really need, flushed the boiler and was pleased to see pretty darn clean water coming out. I do blowdowns on the float-type LWCO about every 10 days. Just maybe a pint, to ensure that the float drops, kills the flame and triggers the water feeder (I have the water feeder shut off with ball valves since I don't trust automatic water feeders, and I manually trigger it to make up for the blowdown water). I put one tablet of Steam Master in at the start of each heat season. Sight glass is perfectly clean and water is very light purple. Although this boiler is grossly oversized to my radiation, with good main venting, well balanced radiators, and a vaporstat upstream of the pressuretrol, I don't allow the boiler to build more than 8 ounces of pressure before it cycles off on pressure. Outside of extremely cold days (we're in Central Pennsylvania), I cycle on pressure just two to four times on any call for heat. I can live with that.

Anyhow, I have searched for and read many HeatingHelp forum posts about buzzing gas valves. I can't find any mention of whether the gas valve buzz in those posts is continuous or intermittent on/off.

So, I did a few things and I hope that I have not introduced too many variables to make diagnosis difficult. First, I turned the thermostat from the heat to the cool setting. I then turned it back to the heat setting and lowered the temperature down to 60. Since the room temperature was 64, the thermostat did not call for heat. During the time that I changed the stat from heat to cool and back to heat, with the temp turned down to 60, there was no call for heat and no buzzing from the boiler. I then moved the stat temperature back to 69, the stat called for heat and the on/off/on/off buzzing started again but the boiler did not fire. Since I was upstairs when the thermostat started calling for heat again, I couldn't hear the typical relay click from down in the basement that always immediately follows a call for heat, but I assume the relay did its thing and made its click to get the party started. With the stat still set to 69 and the stat actively calling for heat, I turned off the 120v master power switch on the boiler jacket. The intermittent buzzing stopped and the automatic damper closed itself. I waited 60 seconds, turned the master switch back on, the automatic damper opened, and then I heard the relay click in the boiler, I heard the gas valve open, the flame ignited, and the gas valve turned up to regular, full, steady state. No buzz at all. None. I have tried to replicate the buzz by turning the stat off a few times and by turning the boiler master switch off a few times. But the buzz has not returned. After a few hours of continuous call for heat, the temperature returned to the set temp of 69 (albeit with little downtime periods during cycles on pressure). Everything seems to be working just fine now.

One more thing to note. Two weeks ago, I was away for a week and when I got home, my wife mentioned that one morning the house temperature had fallen to the low 60s. I asked what she did. She said she had not touched the stat before the temperature fell. She said within a few hours the house was warm again. She didn't go into the basement and she didn't hear any buzzing, since it's a big old house and you have to be in the boiler room to hear any sound from the boiler.

So, I am assuming her experience was caused by whatever condition caused the temperature drop today and the buzzing that I heard. I am not sure why the non-firing condition resolved itself when I was not home. And I am not sure if my cycling the stat and turning the master 120v boiler power switch on and off is what cured it today for me. Dunno. Many variables make diagnosing difficult.

Very long post -- but I wanted to provide all necessary details for diagnosis. With this information, can any of you good doctors offer a diagnosis? I hate to just fire the parts shotgun and replace boiler parts that might not need replacing, and on top of that I am a thrifty dutchman so I want to know precisely what's wrong before I replace anything.

I think the key to diagnosing my problem is knowing that the buzz I heard was a very regular rhythmic on/off/on/off and not a continuous buzz. Though the posts I read about buzzing gas valves didn't mention an on/off/on/off buzz, I assume the gas valve buzz is constant, or others would have mentioned hearing on/off/on/off.

Let the diagnosing begin, and many thanks to all you great contributors to this forum.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    I'm thinking intermittent ignition which isn't igniting for some reason -- but I'm not much on gas burner ignition problems.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Hap_Hazzard
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    There may be or not be a relay just inside the boiler that if buzzing you could feel with your fingers.

    Is the spark doing the buzzing? You might be able to see it.
    It should be a long continuous sparking buzz.

    You might check connections on the ignition module and pilot assembly.
    Just unplug and reset connections one at a time, that can cut thru any corrosion that you can't see.
    CLamb
  • ratio
    ratio Member Posts: 3,627
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    Sounds to me like a spark rod not proving the pilot flame, due either to a bad flame sensor (pilot is lit but not sensed) or the pilot not lighting (clogged pilot orifice, etc.) You can easily tell by looking to see if the pilot is lit (bad sensor) or not (bad pilot). The sensor can be cleaned by removing it (make sure the power is off) & buffing it with a dollar bill—this will often get it going, at least until a replacement can be ordered. Clogged pilot orifice is more involved, and at that point it could also be a bad gas valve.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,840
    edited January 2022
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    I remember hearing that rhythmic buzz coming from an ignition control. I'm not sure which control does that, but I do know there is one that has that on/off/on/off sparking action. It is normal. the buzzing stops once the flame is proven. Since you have no heat, I'm guessing that the flame proving circuit is not working. Is it not proving because there is no flame to prove? Is there a flame and the flame rod is dirty? Is the control not opening the gas valve? is the valve opening and the control sensing circuit not operational? A professional repair technician would be able to solve this.

    If you are a DIY kind of person, you could clean the flame sensor, otherwise, you might need a new ignition control. An the last thing I would check is: if the gas was turned off for some reason. The reason i would check that last... that is too obvious. Why would anyone turn off the gas?

    Three times my friendly competitors have called me to solve a problem where they could not find out why the boiler would not light. After changing controls or cleaning pilot burners or rewiring something like a zone valve. I was the "Go To" control repair guy that the local supply houses might recommend to their professional customers. Three times I found gas meters locked off. Not the first thing you would think of when the heat was working yesterday, and suddenly not working today!

    As a customer, how dumb do you feel when 2 different contractors have visited only to find out you forgot the have the gas company unlock the meter. All three were a new tenant, forgot to put the gas in their name. Three different contractors, with three different locations on three different years
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Motorapido
    Motorapido Member Posts: 307
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    Update. The boiler worked for a few hours and then got stuck again in the no-heat/buzz sound condition. The on/off/on/off buzz seems to be coming from the pilot flame area. I can see the pilot flame ignite. When I flick the 120v master power switch to the boiler while the stat is calling for heat, I hear a relay click and the pilot lights and I hear the buzz sound. The pilot ignites and keeps its nice pilot flame burning happily and properly, but the gas valve does not open and I just hear the on/off buzz. I should note that this buzz is very faint. I can't find my mechanic's stethoscope so I touched a screw driver to the body of the gas valve and the handle to my ear, but it does not seem that the buzz comes from the gas valve. I can't get the screw driver stethoscope substitute down to the pilot body to see if I can pinpoint the sound as coming from the flame sensor area. You really can't hear the faint buzz at all unless you are very close to the boiler. I think this points to the flame sensor. It's hard to see from the bottom of my 63 series, but I see an orange, thick wire coming out of the electronics control box and it goes down under the gas fire tubes and ends in an orange boot like a spark plug boot. It looks like there is about a 2 inch stick of metal that sticks up into the pilot flame, which I assume is the flame sensor. First, note than I am very mechanically adept, having restored countless 1950s and 1960s motorcycles, including all their primitive electronics, and I can do pretty much any kind of DIY repairs, and I'm very precise and cautious. Before I mess around trying to figure out how to remove what I think is the flame sensor, so I can gently clean it with a dollar bill and NOT with sand paper or solvent, can somebody instruct me on how to properly remove that sensor so I don't break it? Again, it's a Peerless 63 series steam boiler.
  • Motorapido
    Motorapido Member Posts: 307
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    Gas pressure seems to be fine in the house. Tankless gas water heater works fine. Gas cooktop works fine. So no utility issue with gas delivery.
  • Motorapido
    Motorapido Member Posts: 307
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    I can't find an ID number/model number on the gas valve and I can't seem to find it in Peerless literature. Anybody know the proper gas valve for a Peerless 63-06 gas boiler, just in case I need to buy one?
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    The spark will continue if it does not sense the pilot flame.
    Cleaning the flame sensor may correct this.

    Power and gas off first:

    To remove the complete pilot assembly, you must first remove the plate above the burners, usually 2 screws in keyhole slots.

    Then it is a pretty obvious removal at this point.

    Then you should see 1-2 screws that hold the assembly in place.
    The aluminum pilot tube connects into the gas valve with a ferrule nut, maybe a 7/16.
    The wires, spark and flame sensor you would disconnect from the module, there may be a ground wire from the pilot to chassis.

    Then clean the flame sensor with stainless steel or a dollar bill.
    The pilot flame hood is also part of the electronic circuit for the flame sensor, it should be cleaned also.
    The spark rod should be cleaned.

    Both of these have porcelain insulators that should be clean and not cracked ( think spark plugs).

    You can blow into the disconnected tube to see if the pilot is clear, it has a tiny orifice in it so hard to blow thru.

    The 1/4" aluminum tubing is easy to kink, the ferrule nut is screwed into an aluminum gas valve so easy on tightening it, they will strip out. That is a break away ferrule nut meant to limit torque on initial install, just to give you an idea.

    Grounding of the flame hood is important because the flame sensor works thru flame rectification.
    The module sends out an AC signal that when it passes thru the fire of the pilot flame it is rectified into DC power and the module sees this and continues the sequence of opening the gas valve.

    So any ground connection is important for operation. There may not be an actual grounding wire but relies upon the pilot tubing.

    MotorapidoHap_Hazzard
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,840
    edited January 2022
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    @JUGHNE has got this. Your pilot is where the flame sensor is located. If you have the mercury flame sensor like this one, the buzz buzz buzz is normal until the sensor heats up and changes the switch to open the main gas valve, and stop the ignition.

    You don't want to touch the source of the noise with a screwdriver or stethoscope. That is a 6000 volt spark and that can pinch you a bit... ask me how I know!

    https://www.amazon.com/Emerson-3098-134-Mercury-Flame-Sensor/dp/B000LDG6DG/ref=pd_lpo_1?pd_rd_i=B000LDG6DG&psc=1

    if you have one of these, you may want to have a pro change all these parts.


    https://www.supplyhouse.com/Resideo-Y8610U6006-Intermittent-Pilot-Control-Conversion-Kit-for-270000-BTU-Units?gclid=Cj0KCQiAip-PBhDVARIsAPP2xc2kO2eak676B05yDBux-xhkUWR4xl5TNOjZV0MKA5ocQp-bra6q5TYaAkZ2EALw_wcB

    This is a kit that will upgrade to a more affordable flame sensor if it fails in the future. I have had experience with the white rogers or emerson brand mercury flame sensor. A customer that has one replaced by me and it failed within 1 year. I replaced it again under a warranty my company provided on repairs. It failed again the following winter. Three failures (the original and two replacements) within 2 years. Did the pilot flame get hotter and make them fail? Did the replacements come from a batch of bad ones? They were not very popular in our area and the supply house said that I was the last one they sold the previous year.

    Anyway, the cost of the part is getting higher and higher every year. Mercury being found a problem for control parts and all.

    Just a suggestion.

    If that is the type of control system you have




    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Hap_Hazzard
  • Motorapido
    Motorapido Member Posts: 307
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    Excellent. Thanks, Jughne. OK, so I remove the metal bar/plate at the front of the boiler that sits on top of the flame tubes, right? After that, I could pull out the tube that contains the pilot. However, it looks like I can't remove that tube since the aluminum pilot-gas tube connects to the pilot on the burner tube. So you're saying that to pull out the flame sensor, I need to remove the pilot gas tube from the gas valve body, which would then allow me to remove the entire flame tube that the flame sensor is in? Or can I just remove the flame sensor from the bottom of the flame tube without pulling out the tube?
  • Motorapido
    Motorapido Member Posts: 307
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    @JUGHNE has got this. Your pilot is where the flame sensor is located. If you have the mercury flame sensor like this one, the buzz buzz buzz is normal until the sensor heats up and changes the switch to open the main gas valve, and stop the ignition.

    You don't want to touch the source of the noise with a screwdriver or stethoscope. That is a 6000 volt spark and that can pinch you a bit... ask me how I know!


    So the flame sensor is the stick attached to the coil of wire? How do I remove that entire unit to clean the flame sensor stick? Do I have to pull out the entire flame tube, or can I just disconnect and remove that assembly without removing the flame tube?
  • Motorapido
    Motorapido Member Posts: 307
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    Here's my spark ignitor and pilot, in all their glory. Man, phone cameras are amazing these days. Does this pic help diagnose the proper removal process so I can clean the flame sensor?
  • Motorapido
    Motorapido Member Posts: 307
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    And two more pics

  • JUGHNE
    JUGHNE Member Posts: 11,061
    edited January 2022
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    I think the best is to remove the entire pilot assembly.
    AL tubing off the gas valve
    2-3 wires off the ignition module...take a picture if unsure where the wires go back.
    and 1-2 screws to remove the entire assembly.

    The flame sensor is a straight SS rod thru an insulator
    The spark ignitor is also stainless steel, perhaps bent at the end so spark will jump to the flame hood,

    If you by chance you unscrew the tubing from the bottom of the pilot burner (not recommended) there is a small orifice that is easy to lose.

    I am fairly sure you do not have the mercury switch shown above, that is from the 80's or so.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,840
    edited January 2022
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    From that picture, I can tell you DO NOT have the mercury flame sensor I described. You will want to clean the flame sensor rod with emery cloth. That is the electrode connected to the orange wire. Or you can have a pro do it.

    Turn off the boiler at the main switch. Let the parts cool down . Then follow @JUGHNE instructions above
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Motorapido
    Motorapido Member Posts: 307
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    From that picture, I can tell you DO NOT have the mercury flame sensor I described. You will want to clean the flame sensor rod with emery cloth. That is the electrode connected to the orange wire. Or you can have a pro do it.

    Turn off the boiler at the main switch. Let the parts cool down . Then follow @JUGHNE instructions above

    Is fine emery cloth OK for my type of sensor? Or should I try the dollar bill cleaning method? I have some CRC electrical contact cleaner that claims to leave no residue. Would that be safe to try, followed by a gentle wipe with a soft cloth?
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    Many use a dollar bill which is actually cloth, not paper.
    Emory cloth may leave some metal oxide on the SS.
    I use a SS brush and finish up with a Scotchbrite fine sanding pad, nylon or synthetic material.

    How about a picture of the assembly showing all connections and also a picture of the control module.
    Hap_Hazzard
  • Motorapido
    Motorapido Member Posts: 307
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    See pic. I see the pilot assembly with its gas supply line. I see the spark/ignitor assembly, with the white ceramic insulator and a spark-plug style tip. So where the heck is my flame sensor? Is it built into the spark ignitor body? I thought I would see three things on this burner tube: 1. pilot body. 2. Spark/ignitor. 3. Flame sensor. So where is my flame sensor?
    Also, if my flame sensor is busted, what senses that the pilot is successfully lit? When I make the stat call for heat and turn on the 120v master switch to the boiler, I hear the valve click to turn on the pilot gas, the pilot lights, and the pilot stays burning. And I hear he very faint buzz/buzz/buzz on/off/on/off buzz sound, that seems to be coming from the general area of this particular gas tube with the pilot and ignitor.
  • ratio
    ratio Member Posts: 3,627
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    The spark rod doubles as the flame sense rod. If it were me, I'd take a pic of that pilot assy & go to a supply house (or supplyhouse.com) & order a replacement (it'll be the whole thing that attached with the two screws, not just the rod). Then try to clean up the rod with the spark plug connector on it & the hood that wraps up over it, it looks like it's dirty enough to interfere with the flame proving, which sounds like what the is problem.
  • Motorapido
    Motorapido Member Posts: 307
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    Forgot to mention -- there are two wired connections to this tube. There is a green ground wire attached to the front end of the gas burner tube, and there is an orange sparkplug-style wire connecting to the ignitor. That's it. Nothing else connected to this tube. And I don't see any wires or mechanisms connected to any of the other tubes.
  • Motorapido
    Motorapido Member Posts: 307
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    ratio said:

    The spark rod doubles as the flame sense rod. If it were me, I'd take a pic of that pilot assy & go to a supply house (or supplyhouse.com) & order a replacement (it'll be the whole thing that attached with the two screws, not just the rod). Then try to clean up the rod with the spark plug connector on it & the hood that wraps up over it, it looks like it's dirty enough to interfere with the flame proving, which sounds like what the is problem.

    Gotcha. So I'll use a dollar bill to clean off the metal electrode on the ignitor, I will clean up the connection point on the ignitor that connects with the spark plug style boot. And I will buy the entire assembly just in case the cleaning does not prove to be efficacious. If I need to install the new part assembly, that will mean removing the aluminum pilot gas tube from the old assembly and attaching it to the new. Somebody posted that you have to be very careful here because there is some sort of loose orifice that sits inside the pilot assembly. Any special instructions for me on swapping out this assembly in a way that I won't mess up or dislocate whatever that loose orifice is inside the pilot assembly?
  • ratio
    ratio Member Posts: 3,627
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    The orifice is caged. The brass (male) compression nut threads into a fitting (hex-shaped outer) that holds the orifice into the (round) pilot body. The only real gotcha's are damaging (kinking) the Al tubing and cross-threading the compression nut.
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    While you have that out, I would recommend getting those 2 screws loose, some some penetrating oil needed. They look cooked so don't twist them off. Sometimes just a nudge of tightening first, then unscrew. Take caution of the spot weld of the piece attached to the burner. Back up cresent wrench recommended on the plates until screws loose.
    Usually leave the burner in place and just remove the screws.
    Make certain the burners are seated in their spots.

    Those screws and the plate to plate contact establish your ground path back to the green grounding wire.
    So clean the plate surfaces up also. This ground connection is just as important as an automotive type ground wire, has to be good or things don't work.

    The single insulated probe first sparks, sparks while pilot gas is on for a second or so.
    Then stops sparking and become the flame sensor. This all happens in a short few seconds.

    Every thing around the pilot needs cleaning, SS wire brush works.
    A little air pressure around the pilot burner and down around the electrode rod to clear junk would be good.

    If no flame then becomes sparky again to repeat the process.

    If you get a replacement you will see the situation with the orifice.
    A factory replacement may come with a new 1/4" pilot tube attached.
    bucksnort
  • Motorapido
    Motorapido Member Posts: 307
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    Update: My local HVAC supplier counters (large, commercial suppliers here in the capital city of the sixth largest state) do not stock this pilot/igniter assembly, including a supplier that stocks tons of Peerless stuff. Dag. I ordered one, and it will arrive in about 5 days. Meanwhile, I followed the helpful instructions listed here, blowing around the igniter base and around the pilot, ensure the pilot orifice isn't clogged. I carefully cleaned the metal rod off the ignition stick. I removed the screws holding the assembly onto the burner tube bracket, I scuff sanded the mating surfaces to ensure excellent conductivity, and I also cleaned the ground wire where it attaches to the tube. I put everything back in place, and voila -- the pilot lit and the gas valve turned on full gas and my grossly oversized boiler is back in the business of oversupplying my radiators with steam. Hallelujah. When the replacement assembly arrives, I'll install it and if my boiler has continued to fire successfully after my work cleaner the old parts, I'll keep the old assembly as an emergency backup. I sure do appreciate the excellent advice that everybody offered in response to this thread. This is by far my favorite technical/mechanical forum, thanks to all of you.
  • Motorapido
    Motorapido Member Posts: 307
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    Argh. The pilot/ignition assembly that I cleaned and reinstalled seems to have failed again. Seems to have fired the boiler for about five minutes, then quit. I should have stayed in the boiler room the whole time to monitor, but I didn't. Went back upstairs. When I went back down to check, the pilot was on and the sparker was making its noise, but no gas to the burner tubes. I could feel that the boiler had been on long enough to come close to making steam, but it shut down the burners before steam reached the main vents. Looks like I'm stuck until the new pilot/ignition assembly arrives. Luckily I have mini split air conditioning with heat option, so I can keep the house warm that way while I wait for the part.

    Any remote possibility this could actually be a bad gas valve? Not sure hot to diagnose that versus a bag pilot/ignition assembly. Thoughts?
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    Well, we tried. :/

    See what the replacement does for you.
  • ratio
    ratio Member Posts: 3,627
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    Check for 24 VAC to the gas valve main terminal (MV) to see if the control is calling for it to be open (bad valve) or not (flame sensor).
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    I strongly disagree with your posting.

    Ratio did not say that the flame sensor acts as a thermocouple.

    It senses the presence of a flame by means of flame rectification of an AC current to a DC.

    If you read more of the post above, I believe this is explained.

    Thermocouples have not been used in heating appliance for many years.

    And also they are used only with standing pilots....they are not available in most heating appliances of today.

    The first paragraph at the top of the posting states the boiler is 10-12 years old.
    That was about the era of the end of standing pilots and thermocouples for boilers and furnaces.
    Yes, still used in some water heaters and other places.

    Read all of the post and then Goggle flame rectification.....developed over 50 years ago.
    WMno57
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
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    While you've got this apart, it might be a good time to make sure all your burners are clean. You should check them at the beginning of heating season, but since you've got the one with the pilot light out, you might as well take the rest out and check or clean them. The rest are easier to remove. If there's too much crud in the slits on top of the burner tubes they won't work right, and you might get flame coming out of the the manifold spud.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    tommay said:

    Jughne, if you are heating it, and it is creating a current then it is acting like a thermocouple.

    Yes, that statement is true.
    But we are talking apples and oranges here.

    Heat has nothing to do with this process and also we are not creating a current.

    The flame becomes part of an electronic circuit, (created/produced by the control module) that actually rectifies a small alternating current flow into a direct current flow to return to the module which will in turn keep the gas valve for the pilot energized. Then after having proven the flame, will open the main valve.
    This returning DC is monitored by the module. It can range from 2 up to 15 microamps, depending upon the system.
    When that return signal is lost or below the holding threshold as required by the design of the module, the gas valve, both PV and MV will become deenergized. This typically happen within 1-3 seconds.

    One reason that thermocouples went away because they can require up to 45 seconds to cool off and stop the production of current that is energizing a magnetic coil holding a valve open.

    45 seconds of non burning gas flow is a serious issue if for instance you had a 2 million BTUH burner.
    Especially if using propane.

    The main reason for the loss of T-couples in smaller equipment was the requirement to eliminate the standing pilot which went hand in hand with the T-couple.

    This was a great simple method of burner control that is almost no longer furnished in OEM production.

    Use the search function at the top of the page for "flame rectification" to read several discussions on the topic. Various applications and solutions.

    WMno57ethicalpaul
  • ethicalpaul
    ethicalpaul Member Posts: 5,702
    edited January 2022
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    It's not creating current. Thermocouples of days gone by created tiny current by using dissimilar metals and flame, but recent proving systems detect a current that flows through the flame (from a voltage generated by the igniter).

    I found this by following @JUGHNE's advice to google it. I never really understood the difference before that.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el