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Thread: Flame Roll-Out

  1. #1
    Stan Williams's Avatar
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    Default Flame Roll-Out

    We have a 17 year old Lennox G24M gas furnace. Over the past weeks, after hours of running well in cold weather, we will get a Flame roll-out switch open indication on the indicator LEDs on the circuit board. We're in a (one-story) ranch with a chimney lining and a vent fan blowing exhaust up the pipes. No basement. The burners have no rust or white residue on them or the entry to the heat exchanger pipes. We have a CO sensor next to a floor vent (just tested it) in a bedroom 20 feet away, batteries good, no CO sensed. There are three Roll-out sensors, one in the heat exchanger compartment, and two above the burner tray. The roll-out sensors reset by cycling power to the furnace (and thus the ignition control board.) The air supply is through the attic, via a 14" x 14" grate when the furnace room (3' x 12' at the base of the chimney) door is closed. The grate is clear, the attic is ridge vented.

    I'm curious if I'm getting some minor flame roll out between the burners. I'll attach a picture with the area in questioned circled in red. While burning there is flame between the burners fluttering about 1 inch off the flange that holds the burners; this flame off the flange is continuous with the flame coming off the burners.

    I've watched the furnace burn through a cycle and the only sort of flame I see that is not dead center in the burners going into the heat exchange pipes is indicated on the attached photo.

    any ideas what is causing the occasional roll-out switch open. I've never been watching when it happens, as the "open" will occur hours apart.

    Thanks.



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  2. #2

    Default Re: Flame Roll-Out

    Your circles are pointing to the carryover/crossovers. That's how each burner is ignited.

    Are you getting any spillage @ the burners. The first thing I would recommend is that you ensure the furnace isn't over- fired.
    You should have a 2 cu. ft. dial on your gas meter. Fire up the furnace, run it for a while, then go outside and rate/ time the furnace. To do so, you'll have to shut off all other gas equip. in the house (including standing pilots).

    Pick a point on the upswing side of your index. When the dial hits that mark, start your timer/ stopwatch. Time the dial for a min. of 1 revolution (10 segments).

    Take that time it takes to make a full rev. and use this formula:
    Dial size (2/1) x movement (1) x 1 hour/time observed x the btu rating for a cu. ft of gas in your area) equals the rate at which your furnace is running. The answer should be somethere from 40-150k btu's/hr.

    Example: A furnace is timed/rated on a 2 cu. ft. dial. The dial makes a full revolution in 76 seconds (3600 seconds in an hour) and my local gas co. gas is rated @ 1050 btu's.....

    2/1 x 1 x 3600/76 x 1050= 99,473 btu's/hr

    Check your btu input rating for your furnace (will be listed on the furnace) and make sure it's not over- fired, and no less than 5% under- fired. If over- fired, that may be causing your issue.

    There's a lot of things that could cause your rollout switches to trip-- is it always the same one?


  3. #3

    Default Re: Flame Roll-Out

    Are you sure it's the roll out switches tripping?? Reason I ask is that rollout switches are typically manually resettable only- the one I can see is a manual reset one. Oftentimes, the indicator light will say something like (open 24 v circuit-- rollout/ hi limit, etc.) If it's manually re- setting after a while, you're probably tripping on hi limit or auxillary limit due to over- heating (air flow issue most likely).


  4. #4
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    Default Re: Flame Roll-Out

    Brandon, thanks for the ideas. I suspected that the flame between burners was the mechanism by which the burners are ignited from the ignition burner at the far right. Thanks for confirming that. Two of the roll-out switches are manual resets as you see in the photo. I have never had to reset those. The only indication I have is that the furnace shuts down, and the EGC LED's indicate (according to the chart on the side of the furnace) "ROLL-OUT SWITCH OPEN". There is one roll-out switch (at least it appears to be) in the side of the heat exchanger casing that does not have a manual reset button on it. If that is designed to fail once and be replaced, then it is still functioning b/c the furnace worked just fine throughout the night. So, yes, it could be some sort of over-heating situation and something else is tripping and the EGC board doesn't know what else to indicate.

    Yes, the indication is always the same, but it is very intermittent.

    I take it that 1050 BTU/cu ft is a nominal value for all natural gas? I can't see that number on my otherwise detailed monthly invoice. But I see it used in other calculations on-line. I'll go time my meter and get back to you. Thanks, again.


  5. #5
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    Default Re: Flame Roll-Out

    Brandon, just ran the calculation. I have a 1cuft meter. That is the dial says ONE CU FT,and is then divided into 10 divisions. If I assume one revolution = 1 cu ft, then using your formula I'm using 145.4 cu ft/hr.


  6. #6

    Default Re: Flame Roll-Out

    Stan,

    I don't think you're reading the error code properly. If it really says "roll out switch open" and that's it, but you haven't had to re- set them, then you may have a bad connection or something. You don't have a true rollout situation, or you'd be re- setting the switch.

    Trace the wires. Do the wires run from the hi limit (third r.o switch that isn't really a rollout switch-- in the heat exchanger area) down to the rollout switches? If so, then you most likely have your furnace tripping on hi limit -- read all of your error codes and see if there's one that says "open 24v/open hi limit, etc.) If no, then I'm even more convinced that you're tripping on limit.

    If tripping on hi limit, the burner should cut out, the blower will run until the furnace cools enough, and then the burners should fire again-- sound familiar?

    First thing you should do is ensure you have all of the heat registers and return air ducts fully open throughout the house, you don't have multiple filters and that the filter system is clean. Also, ensure your blower assembly is clean.


  7. #7

    Default Re: Flame Roll-Out

    As long as you replaced the 2/1 to 1/1 to account for the proper dial size, then I'd say you have a big furnace.


    145.4 x 1050=152,670 btus/hr. Check with your local gas utility to see for sure. Btus are probably somewhere between 1,000 and 1,100 btus/hr.

    Now, look on the plate on the furnace and see what the input rating is....


  8. #8
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    Default Re: Flame Roll-Out

    Brandon,

    Thank you for your expertise.

    Right you are. Upon your challenge I looked more carefully at what I was reading. The control board with the flashing LED's is upside down compared to the sticker on the furnace. (pix below) Thus what was Diag LED 1 is actually 2, etc. And the ACTUAL code (if I figurately stand on my head) is "LIMIT SWITCH OPEN". This is further confirmed by your suggeston that I trace the wires, which I did with the wiring schmatic in hand. What I thought was a flame roll out switch mounted in the heat exchanger casing, is, as you suspected, the limit switch (no reset on it, see PIX below) and the documentation for the board says that is resets automatically. ....but after 60 minutes.

    You asked if after the cool down cycle if the burners come back on automatically. That may have happened. But because the house was getting cold I'd check on the furnace probably before that 60 minutes was up, and recycle the power switch and the system would immediately come back on and heat the house. Yes, the fan could be running while the burners were off (cooling down the furnace.)

    I keep the furnace filter changed... did it just 5 days ago. The ducts through the house are open, etc. Had the ducts and blower "vacuumed out a year ago" but I know they did not do a good job.

    Re: BTU CALCULATION -- I typed my response incorrectly. Using your formula:
    2/1 x 1 x 3600/76 x 1050= 99,473 btu's/hr
    for my situation, I get:
    1/1 x 1 x 3600/26 x 1050= 145,385 btu's/hr (NOT cu ft/hr). Sorry about that.

    The sticker inside the furnace says the input rating is 120,000 (I think) (see pix). What is the difference between AGA/CGA vs. CGA/SUEL ?


    Here are images of how I confused the reading. Both are "right reading" but the board is mounted upside down from the sticker. (I color coded the sticker for this photo)




    Here is the "LIMIT SWITCH" (circled in green)



  9. #9
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    Default Re: Flame Roll-Out

    Brandon,

    So, I guess the question is, "Is the furnace" getting too hot. Is the 120,000 BTUs the minimum the furnace should be putting out, or is that the maximum? (compared to the 145,000 I'm consuming.)

    BTW:
    1/1 x 1 x 3600/26 x 1000 = 138,462
    1/1 x 1 x 3600/26 x 1050 = 145,385
    1/1 x 1 x 3600/26 x 1100 = 152,307

    I hesitate to call my gas company because of the run around I'll get trying to find someone who could ask such a technical question was what the BTU rating is of the gas they supply. I thought it'd be on my bill, or on a website, but couldn't find anything. I grow weary and impatient calling so called "customer service" call centers. Many (not all) of the time, you can't get an answer to a technical question.

    So what's your day job?

    stan


  10. #10
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    Default Re: Flame Roll-Out

    Quote Originally Posted by Stan Williams View Post
    Brandon,

    So, I guess the question is, "Is the furnace" getting too hot. Is the 120,000 BTUs the minimum the furnace should be putting out, or is that the maximum? (compared to the 145,000 I'm consuming.)

    BTW:
    1/1 x 1 x 3600/26 x 1000 = 138,462
    1/1 x 1 x 3600/26 x 1050 = 145,385
    1/1 x 1 x 3600/26 x 1100 = 152,307

    I hesitate to call my gas company because of the run around I'll get trying to find someone who could ask such a technical question was what the BTU rating is of the gas they supply. I thought it'd be on my bill, or on a website, but couldn't find anything. I grow weary and impatient calling so called "customer service" call centers. Many (not all) of the time, you can't get an answer to a technical question.

    So what's your day job?

    stan
    The best thing you could do is to have a local HVAC contractor come out and service your system. Let the professional make the needed repairs. At 17 years of age your system is past its expected life, so it could be more involved than can be diagnosed on a discussion board like this.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  11. #11
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    Default Re: Flame Roll-Out

    Scott,

    Appreciate the advice except...the existence of this forum suggests that there's a need for homeowners to improve their knowledge, take personal responsibility, and not give something as important as a furnace (it's 6 F today) over to a tech who does not have to live in the house and pay the bills.

    I've dealt with too many disreputable techs and companies behind them. And while I'm not an HVAC expert, I do know something about elector-mechanical systems. (I'm an ex NASA electronic engineer who wrote malfunction test and repair procedures for astronauts and designed and built electronic test equipment.) I've had techs bold face lie to me about what the problem is, they've left my furnace with wire runs disarrayed and the circuit board dangling on one stand-off, etc. Horrible workmanship generally. Also techs cannot live next to a furnace operating day-in-and day-out like I do and so they can't do a decent job of diagnosing a problem that is intermittent, as the problem I'm dealing with now is. I've had guys come out (in years past) and say, "Well, it's working fine now. Call me if it fails again. That'll be $65." With this furnace, I'm on my fifth ignition control board and the ones I'VE replaced have lasted twice as long as the ones the techs replaced. (Now if I can just remember that the board is mounted upside down in relation to the sticker, I'll do a lot better.)

    The last time I replaced the board (after talking a Lennox engineer) I mounted it OUTSIDE the hot and vibrating furnace cabinet, onto a wall where it is well ventilated and not exposed to vibrations. I recommend this where possible. Electronic components and epoxy circuit boards don't like heat and vibration, so why mount these boards where there' going to be susceptible to mechanical component and board disintegration?

    I'll call a tech when I can tell him what to do. But I'm past the days of a tech telling me what's wrong. Don't trust them.

    stan


  12. #12
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    Default Re: Flame Roll-Out

    Stan I understand your frustration with service techs but sometimes you just have to trust someone else to the job. In this case unless you have the equipment to measure pressures and air flow you will have no choice.
    http://www.ultimatehvac.com/LinkedDocs/Lennox/9723b.pdf

    The beatings will continue until morale has improved. mgt.

  13. #13

    Default Re: Flame Roll-Out

    Stan,

    Assuming your timer was correct when you timed the furnace, then it is indeed over- fired. But hold on.... How long has this been an intermittent issue? The firing rate of the furnace won't change, so you may have several issues.

    Re- time your furnace for a longer period of time in order to be more exact. Say, 5 full revolutions.

    dial size (1/1) times movement (5/1) times 1 hr/time observed times whatever your gas is rated at in btu's/cu. ft. If it's over- fired, it needs to be fixed by an HVAC tech. Please call your gas co. and ask them. The cust service rep probably won't know, but any of their field tech's will-- it's first day training material......

    Since it's tripping on hi limit, you either have an airflow issue, or a bad switch, which I doubt. Again, make sure all vents/ registers are fully open, that the filter is clean, blower is clean, etc.

    My day job... (gas utility service technician/home inspector).


  14. #14

    Default Re: Flame Roll-Out

    Your furnace's max. input rating is 120,000. Anything higher is an issue. AGA is the American Gas Assocation.

    CGA --- Canadian Gas Association or Compressed Gas Association.

    Last edited by Brandon Whitmore; 01-24-2013 at 06:48 PM.

  15. #15

    Default Re: Flame Roll-Out

    http://www.ultimatehvac.com/LinkedDocs/Lennox/9723b.pdf

    This should be the manual for your furnace...... I didn't spend much time looking at it to be sure.......


  16. #16
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    Default Re: Flame Roll-Out

    Brandon,
    Thanks, I will do as you suggest. The tripping only lasted about two weeks, during some severe windy weather. It has not tripped once since I started this thread with you, although we've had single digit temperatures.

    So, just to confirm my understanding, if running that BTU consumption formula turns up higher than 120,000 BTU I have something that needs adjusting by a tech. Got it.

    I will run the consumption test for longer period, and yes, all vents are nominally open, which means they are as they've been for years. Wife did close some bedroom doors at the thermostat end of the house for a day...which would prevent heat from getting to the themostat. But that was short lived and symptoms were after that.

    I'll check blower area through the humidifier access.

    Be back later tomorrow.

    Thank you.

    stan


  17. #17
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    Default Re: Flame Roll-Out

    Brandon,

    Here's what you asked met to do:

    It took me over 30 minutes on hold and 6 CSR's with our gas company (Consumer's Energy) before I found someone to tell me that the Gas rating here is 100,000 BTU/cu.ft.

    I timed 5 rev of the second dial on the second row (see pix), which took 128 seconds, which puts my consumption at $140,625 BTU/hr.

    Lennox confirms that I should not be using more than 120,000 BTU/hr.

    I disassembled the blower casing and took pictures around the exterior and interior of the fan. There is no residue, insulation, dirt, dust on the fan blades (except some light rust), or around the perimeter. I looked under the condenser into the plenum for the air exhaust and it is clear of any dust, debris, etc. And as I said earlier I replace the air filter (one of those 4 inch think jobs with the multiple folds) 3-4 times a year, and had installed a new filter when this symptom (limit cut off) was observed.

    I have not had a limit cut off in the last four days.

    I will have the gas company (not a contractor) come out and examine the problem, now that I'm satisfied that I've done all I can do.

    Thank you for the patience of walking me through this. I hope you learned something as well... e.g. ask the customer if the diagnostic sticker is upside down or if the furnace is. HA!




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    Default Re: Flame Roll-Out

    Quote Originally Posted by Stan Williams View Post
    Brandon,

    e.g. ask the customer if the diagnostic sticker is upside down or if the furnace is. HA!

    Not to be ugly here Stan, but they did color code it!

    The beatings will continue until morale has improved. mgt.

  19. #19
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    Default Re: Flame Roll-Out

    Vern,

    No, the sticker is not color coded. The color you see in the photo was added by me in photoshop when I posted it on this board. I AM GOING to color code the actual sticker, however. The furnace is actually installed upside down and the sticker is right side up for readability. LOL!

    stan


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    Default Re: Flame Roll-Out

    Quote Originally Posted by Stan Williams View Post
    Vern,

    No, the sticker is not color coded. The color you see in the photo was added by me in photoshop when I posted it on this board. I AM GOING to color code the actual sticker, however. The furnace is actually installed upside down and the sticker is right side up for readability. LOL!

    stan
    You know I was surprised to see a label so fool proof. Didn't notice your note at the bottom of the pic .
    Have you had the regulator valve adjusted yet? (link I sent has handy chart to help with meter calc.)

    The beatings will continue until morale has improved. mgt.

  21. #21
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    Default Re: Flame Roll-Out

    Vern,
    Now that you point out the chart in the operating manual, I see and understand it. And yes, more gas is coming in through the regulator than should, if the pressures are right. I do not have a pressure meter and will get a tech out here to make adjustments. It appears, however, that I will have to get to new regulator as the manual says there are no adjustments, and visual inspection suggests the same. Thanks.


  22. #22
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    Default Re: Flame Roll-Out

    Quote Originally Posted by Stan Williams View Post
    Vern,
    Now that you point out the chart in the operating manual, I see and understand it. And yes, more gas is coming in through the regulator than should, if the pressures are right. I do not have a pressure meter and will get a tech out here to make adjustments. It appears, however, that I will have to get to new regulator as the manual says there are no adjustments, and visual inspection suggests the same. Thanks.
    I don't know about your model but used to adjust at screw where the spring was changed to go from NG to LPG. Last time I did that was X no. of years ago

    The beatings will continue until morale has improved. mgt.

  23. #23
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    Default Re: Flame Roll-Out

    Quote Originally Posted by Vern Heiler View Post
    I don't know about your model but used to adjust at screw where the spring was changed to go from NG to LPG. Last time I did that was X no. of years ago
    Stan see pg. 15, fig. 17.

    The beatings will continue until morale has improved. mgt.

  24. #24
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    Default Re: Flame Roll-Out

    Ah, ha! Am walking it down to 120,000. I'll let you know.
    sw


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    Default Re: Flame Roll-Out

    Quote Originally Posted by Stan Williams View Post
    Ah, ha! Am walking it down to 120,000. I'll let you know.
    sw
    Please note: I did not recommend you adjust the regulator. The adjustment should be done by HVAC tech using a pressure gauge. I was pointing out that you probably do not need a new regulator, just adjustment of the one you have.
    (let me know how it turns out )

    The beatings will continue until morale has improved. mgt.

  26. #26
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    Default Re: Flame Roll-Out

    Will do, Vern. My "adjustments" were not doing anything, indicating I'm over my head. thanks.
    stan


  27. #27
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    Default Re: Flame Roll-Out - Limit Switch Open

    To my friends who so ably helped me diagnosis my furnace here is the resolution. The local utility came out but would not touch the furnace because I had reinstalled the ignition control board (the furnace's 5th) on a wall next to the furnace, thus removing the epoxy board laden with mechanical and electronic components outside the hot-vibrating atmosphere that the Lennox "designers" had placed it. I was told later that recent Lennox ICB have heat sinks on them.

    A Lennox dealer did come, however, and found that the pressure regulator was supplying 5.3 wc of gas pressure to the burners instead of the required 3.5 wc. Further the Honneywell pressure regulator had been adjusted fully closed and was obviously broke, years before. A previous tech (there had been six previous visits by techs, from 4 different companies not counting the installers) had adjusted this baby all the way closed and it was still letting through 5.3 wc. Further, when the current tech went to change out the regulator he discovered that the gas coupling was UPSTREAM of the gas cutout valve. So he turned off the gas to the house, re-plumbed the coupling and valve, and installed the regulator. Out of the box the regulator supplied the burners with 3.5 wc. And since then, no limit open faults. Thank you all. Oh, and with the 3.5 wc, my timing of the gas usage dropped from 140,000 BTU/hr to 126,000 BTU/hr. Yes the furnace is rated at 120,000, so the 6,000 overage must be within the tolerance of the rating, or the gas isn't exactly 100,000 BTU/cu ft.


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