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Lochinvar KHN “too many recyclings” fault

RPK
RPK Member Posts: 119
in Gas Heating
I just started a KHN055 on Friday. Apparently I accidentally left the gas off after removing my manometer during startup testing. The homeowner(also the owner of the company I work for) discovered this and reset the boiler, but then the boiler locked out again after, apprently, failing to ignite 3 times. I am going there tomorrow to investigate, but I want to know more about this particular fault before I go. The service manual says to check:
Louver Proving Switch (don’t have, jumper in place)
Blocked Drain Switch ( was draining okay, needs investigation )
Air Pressure Switch (needs investigation)
Gas Pressure Switch (don’t have one)

Is this list comprehensive, or are there any other issues that will cause this fault. Everything was working perfectly when I completed my startup on Friday afternoon.

Comments

  • delta T
    delta T Member Posts: 884
    did you purge the air out of the gas line? Might take a little bit to get all the air out of the line before the boiler will light reliably.
    Rich_49
  • RPK
    RPK Member Posts: 119
    Yes, the gas line was sufficiently purged. There’s a nicely sized buffer tank, so I got some good runtime on it while I was checking the combustion . I read another post where a homeowner was asking about this same fault. Some of the responses seemed to imply that there was a relationship to this fault and flame failure faults, and also mentioned the foghorning issue). The way I interpreted the manual, this fault only results from specific limits opening repeatedly.

    Would I see the “too many recyclings” fault after repeated flame failures?
  • Ironman
    Ironman Member Posts: 7,556
    Yes. And I agree about air in the gas line.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • delta T
    delta T Member Posts: 884
    What were your combustion numbers set to? LP or NG?
  • RPK
    RPK Member Posts: 119
    Update: To answer my original questions, it seems flame failures will result in the “too many recyclings faults”. The boiler had started doing the “foghorning” thing. It would ignite successfully around 50%, then try ramping down to 15%. At about 20% it would start making some weird noises, the flame would get rough and it would cut out. Five attempts and it would go into hard lockout and display that fault.

    This is on natural gas. The combustion was on the leaner side of the range specified in the service manual (5.7%O2). I would have adjusted it richer on startup, but I loaned my only 2.5mm Allen wrench to a guy and didn’t have a spare (now I have a bag of 10 in my combustion analyzer box). I had planned on a return visit to fine tune, but it was running cleanly, reliably, and within acceptable (albeit less than ideal) ranges when I left it on Friday. I adjusted the combustion until the noise went away. I ended unit at 2.8%O2, (72PPM CO)

    I also noticed that the flue is slightly less than the 12 foot equivalent length minimum. (It’s about 10 feet fittings) What are your thoughts on remedies for this, or should I leave it alone if combustion and ignition are working well? I seem to remember reading somewhere about someone installing a ball valve in the flue and throttling it to increase the friction loss in the flue pipe slightly. I would welcome anyone’s comments on such a practice.

  • delta T
    delta T Member Posts: 884
    Have you checked combustion numbers at low and high fire? I would check it on low fire, my bet is that it is running too lean on low fire and that is causing your problems.

    I would not install a ball valve in the flue, too much liability. Is this a concentric vent kit or just two pipes?
    Rich_49
  • RPK
    RPK Member Posts: 119
    edited October 2018
    Just straight pipe on this, no concentric. Low fire was 6.9%O2 before I adjusted it. Accidentally deleted the combustion report from my phone so I don’t have it with me at the moment, but it was definitely a richer that made the noise go away.
  • DZoro
    DZoro Member Posts: 1,048
    Wouldn't be too concerned with the short piping at this point. What were your CO, O2 and flame numbers on low fire?
  • Ironman
    Ironman Member Posts: 7,556
    Put it at the richest c02 value the manual allows. If it still fog horns, then you're gonna have to enlarge or remove any CSST near the boiler. That's the cause of the fog horning.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • RPK
    RPK Member Posts: 119
    Ended up at 6%O2/8.4CO2/24PPM CO at low fire. 6uA flame signal. This was adjusted rich enough to stop the foghorning, but started to make too much CO if I went any further.
  • Zman
    Zman Member Posts: 7,611
    You low fire numbers are pretty lean. Might make sense to adjust that screw that they tell you not to B)
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RPK
    RPK Member Posts: 119
    Thank you Zman.

    How common is the need to adjust the bias on these? I’ve always adjusted the high fire and only on rare occasions (on Lochinvar Crests, and once on a Camus Dynamax) had to adjust the bias. The Crests all seem to require fine tuning. The Camus had a foghorning issue. I’ve always been reluctant to go beyond what’s described in the manual without permission from a higher authority.

    What is the downside to having the low end on the lean side. Might a richer mix get my flame signal a little higher?
  • DZoro
    DZoro Member Posts: 1,048
    Too lean, your flame signal is poor. Get to "normal" numbers on high fire first. Then go to low fire, very carefully adjust the bias. It doesn't take much. That is where you can get rid of the fog horn, and bring your flame signal up. Should still be able to keep CO in check. Take your time with the bias, it shouldn't take much to affect low fire performance.
    High fire numbers must be in range before adjusting bias "low fire".
    Low fire Co2 8.8%-9.5%, 02 3.9%-5.2%
    Turn the bias 1/8th turn max, to increase CO2 turn bias clockwise.
    If you are in this range in low fire and you still have fog horn issue, then you can go outside of the numbers to take care of the fog horn. Try to keep flame signal above +8, and CO in check.
    RPK
  • delta T
    delta T Member Posts: 884
    Agree, a bias adjustment may be in order. If you do adjust the bias, call tech support and have them walk you through it, they will probably go through the standard procedure first, but when you can't get the numbers, they will okay a bias adjustment. The reason to call them is not because I don't think you know how to do it, but because they will log the serial number and that you performed a bias adjustment under their guidance and with their blessings. Warranty stays intact. If there is ever a problem with the gas valve that falls under warranty, they can deny the warranty if the paint on the bias adjustment is broken if they have no record of doing it under their guidance.

    I have had a couple of kbn's that I had to adjust bias on, but not many.

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