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Lennox/Dunkirk Q90-100 failing to start

carlbcarlb Posts: 10Member
I have a Lennox/Dunkirk Q90-100 gas boiler that sometimes will not start. The control board will start the process and the induction motor will start to rev but will just die and then will try again. This goes on and on with a clicking sound coming from the control board, much like a telegraph key typing. I though it was the board and replaced it but that did not correct the problem. This unit was installed in 2006 to replace a Lennox complete heat system. Since then it has had a heat exchanger, igniter, 2 control boards and high limit switch replaced. If I power it down and let it set for 15 minutes or so it will start up and run fine sometimes for days with no problems other times it will only go a few cycles until the clicking returns. If you leave it alone while it is clicking it may do that for 5 minute to 3 hours and It will start by itself. Any thoughts on what may be causing this?

Comments

  • AbracadabraAbracadabra Posts: 1,948Member
    edited February 2016
    Blocked vent? Flaky pressure switch? Failing motor not achieving enough air velocity/pressure? A multimeter while on-site should be able to narrow down what's happening
  • carlbcarlb Posts: 10Member
    Vents clear. Suspect the switch, but didn't know if it would produce the erratic condition. The motor seems to run fine when it finely kicks in.
  • IronmanIronman Posts: 4,902Member
    You need a COMPETENT tech with a DMM and a manometer to properly diagnose it. ''Seems to" is not a diagnosis. Neither is endless parts changing.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • carlbcarlb Posts: 10Member
    Thanks for your input Ironman. Truth be told I did have 3 COMPETENT techs here on MULTIPLE occasions, two of which were Lennox dealers, all of which could not find the problem. I'm not sure if the reason they can't seem to find it is because the problem is so intermittent or what. They checked the vent and the gas input and the gas valve. I did not certify the tools they used but would presume they were proper for the job they were doing. If you are familiar with the Lennox Complete Heat systems you know they were a POS. This unit supposedly was the "savior" because of it's reliable operation. Even though parts were warranted on both units the service calls were not. So it has come to a point that I can just as well unscrew, unplug and replace a part as efficient as the service techs seem to be able to do, and without the minimum service charge. My goal of asking the question here was to see if anybody had a similar issue and what happened to fix it, or do I need a SPECIALIST instead of a COMPETENT tech to get it corrected. I'm not opposed to throwing a couple of parts into it and see if it fixes it, I just don't want to keep paying service call after service call with nothing to show but money flying out of my pocket. Again I thank you for your input.
  • AbracadabraAbracadabra Posts: 1,948Member
    "3 COMPETENT techs"

    things that make you go hmmmm..

    I don't like trash talking other people, but if they were compentent they wouldn't be changing parts endlessly. If it's not happening when they make their service call... well... that's another issue.

    I assume this is something that has started happening recently?

    Intake and exhaust on same side of building?
  • IronmanIronman Posts: 4,902Member
    Was the boiler ever setup using a digital combustion analyzer? Do you have the results?
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • carlbcarlb Posts: 10Member
    To Abracadabra; 1)The exhaust and intake are on the same side of the building right next to each other. 2)The problem was noticed a couple of years ago and the control board was changed which seemed to resolve the problem, although due to the intermittence of the issue it may have been going on and just wasn't noticed. It has now become more noticeable within the last six months again.
    To ironman: I was not home to see the entire installation so I do not know if they conducted that test, there was no paperwork that indicated that. I felt back when it was installed since they were Lennox service techs they would have know how to correctly install their boiler. That may have been a mistake on my part!
  • IronmanIronman Posts: 4,902Member
    edited February 2016
    That boiler has a negative pressure gas valve as do all mod/cons (though it doesn't modulate). It is required that it be properly setup with a digital combustion analyzer when commissioned. The fact that the techs who installed it worked for a Lennox dealer does not mean that they've had specific trading on the boiler, or that they know hydronics or even have or know how to use a digital analyzer. Most of them are mediocre scorched air people. Yours may have been better, who knows. The fact that they didn't leave a printout from the analysis indicates that none was done.

    Your problem may or may not be related to proper combustion, but you just haven't provided enough info to make a diagnosis over the net. And, you probably can't. That's why I stated earlier that a competent tech with the right tools needed to be on site. It sounds like your Lennox guys have been replacing a lot of parts in attempt to fix it and you're tired of it (understandably), but you're actually embarking on the same path.

    If you'd post some pics of the boiler, it's near piping and a closeup of the boiler with the door off, we might see something obvious and could help. Also, what type of gas?
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • carlbcarlb Posts: 10Member
    Here are some pics and a vid of the cycling issue.
  • AbracadabraAbracadabra Posts: 1,948Member
    Don't see a video
  • carlbcarlb Posts: 10Member
    Having problem attaching vid, working on it
  • carlbcarlb Posts: 10Member
    Not able to upload the vid which is to bad as it was a great example of what is going on.
  • kcoppkcopp Posts: 3,324Member
    load it to youtube then post the link.
  • carlbcarlb Posts: 10Member

    Here is the link to what this things sounds like when it is cycling. If the power is turned off for 15 minutes or so it will cycle through and run fine. If I let it click like its doing, eventually it will start and run for weeks, days or an hour and start doing this all over again.
  • IronmanIronman Posts: 4,902Member
    There's a sequence of operation when there's a call for heat:
    1. The inducer starts
    2. The pressure switch(es) prove proper draft
    3. The hot surface ignitor heats up
    4. The gas valve is energized for 6 seconds
    5. If flame is proved within those 6 seconds, then the gas valve remains energized until the call is satisfied unless interrupted by a safety.

    The LED lights on the board tell you what's happening during the sequence and will also indicate what safety caused a lockout. You need to watch it through the sequence and determine at what point the sequence is interrupted.

    A clogged condensate line will cause the pressure switch to remain open or fluctuate.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • carlbcarlb Posts: 10Member
    No lights other than the green power light is on when this cycles. If it starts then the two red lights along with the green light are on. I did not check the condensate line though, something to investigate tomorrow.
  • Empire_2Empire_2 Posts: 2,343Member
    Ironman nailed it. Just listening to the sound clip you provided it just may be that the condensate line is not only plugged, it is backing up into the induced draft housing or close to it. Disconnect vinyl tubing and clear any blockage. You can use a wet dry vac to suck out the blockage along with any water that is causing pressure switch to make and break due to the blockage. This should bet you going until a tech. Can clean properly. Now, having said that, I am not there.lol but that's what it sounds like to me. It's been a while since I laid eyes on a Q 90, but give it a shot. Also get a level out and make sure exhaust line is pitched back to the boiler. Let us know how you make out.

    Peace:
    Mike T.
  • Empire_2Empire_2 Posts: 2,343Member
    Just a side note. When you are letting the system sit for 15 min or so, condensate is draining slowly and clearing. Defiantly get all tubing cleaned out. These boilers should be checked once a year and like ironman stated, and a combustion analysis must be done to assure safety and reliable operation.
  • Empire_2Empire_2 Posts: 2,343Member
    Ironman, I did a little research and it looks like the Honeywell gv VR8205 is on parts list at a 2.5"wc pos... manifold pressure. Now unless there was a revision after 2006,.... then maybe not. I could not get any further info.
  • todd_ecrtodd_ecr Posts: 91Member
    Can you get a closer pic of the control board and wiring?

    Gas valves on these are positive pressure. Spec is 2.5"

    Certainly a pressure switch bypass test will give you direction. Jump the pressure switch wires together AFTER the inducer starts. Give us the results of this test and I will give the next step to take.
  • IronmanIronman Posts: 4,902Member
    Empire said:

    Ironman, I did a little research and it looks like the Honeywell gv VR8205 is on parts list at a 2.5"wc pos... manifold pressure. Now unless there was a revision after 2006,.... then maybe not. I could not get any further info.

    Yeah, I saw it after I posted. The 125 - 200k btu models are negative pressure gas valves.

    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • carlbcarlb Posts: 10Member
    Well here's the update. I cleaned out the condensate lines and the problem appears to have disappeared. I have seen some names on this board who are experts from the Dunkirk and Utica boiler companies with regards to this model boiler. I think my next move is to contact them and see if there are techs in my area who are "competent" to test this boiler. Thanks to all for the help.
  • Al_BW90Al_BW90 Posts: 1Member
    I have a follow-up question here:

    I am experiencing problems with a violent ignition. You can see this in the video below.



    It is more violent when the system is starting up from cold and gets better after the system gets hot.

    I'm stumped. What could be creating this problem? The vinyl condensate tube at the bottom is clear, and water in the tube does not get pulled up to the chamber bottom when the fan gets going. One thing that irks me is that there is no sediment trap on the gas line, which I will be adding.

    What do you think this could be?

    And thank you!
  • DZoroDZoro Posts: 723Member
    @Al_BW90
    Start a new discussion for clarity of your situation, and easier responses.
    D
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