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Bump......KBN 106 Repeated Lock out with "Outlet Temp Diff"---Red screen--Manual reset

JUGHNE
JUGHNE Member Posts: 11,322
edited February 3 in THE MAIN WALL

This was new install 9-6-2013.

2 lockouts in 2016….maybe high temp.

Lockouts in 2019…..dual sensor (4 wire) outlet probe TST20009 changed

Lockouts in 2020 for high temp water out….both sensors had consistently tested with range.

Main board was replaced as the next step.

2021……System pump current draw dropped from 1.8 to 1.1 amps. Pump replaced.

All good until 2024. Then "Outlet Temp Diff" lock outs starts. What is confusing is that the temps displayed match. 86/86..118/118…99/99….134/134 and so on.

Again ohm readings are in line with temps. Readings taken right at the Molex pins that plug right into the board.

System pump replacement in 2021 corrected problems for 3 years.

This year the boiler pump (high speed) when dropped to medium speed would cause the boiler to rattle from lack of flow. So new boiler pump. Old pump was not an easy spinner and the rotor would not shift back and forth as you can hear with a new pump.

This gave about 10 days of good operation after that change.

Both pumps are UPS26-99F, 3 speed on high, check valves removed.

Burner water tube cleaning also gave about 10 days of joy.

Boiler opened and cleaned every 2 years. Credit card crud cutting and rinsing….approx 4 hours to "saw" between each coil.

Never a flame failure or failure to light, spark and flame sensor cleaned with every opening. New target wall this year.

Any ideas?? I believe there was a similar posting here in the past….without any answer to this problem. Thanks

Comments

  • hot_rod
    hot_rod Member Posts: 24,202

    scaled up inside the boiler hx? Is it piped primary secondary?.

    With the wider delta that boiler can operate with a 15-58. So the 26-99 should be plenty.

    Is there a y strainer in the system?

    A partially plugged air sep? We've seen a few of those here recently.

    Seems like a flow issue to me.

    Screenshot 2024-12-06 at 8.13.26 PM.png

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Big Ed_4
    Big Ed_4 Member Posts: 3,102

    I wonder if the fuel is different … Here on Long Island I never found one that I had to use a sword …Hmm

    There was an error rendering this rich post.

  • 109A_5
    109A_5 Member Posts: 2,036
    edited December 2024

    Hello JUGHNE,

    Well it would not surprise me if one of the sensors has a spot at a certain temperature that its resistance changes incorrectly. Automotive sensors have this issue, it may be a thermistor issue or the constant heat cycling compromises the connection to the thermistor.

    Molex pin fitment issues, also the crimp to the wire to the Molex pins. I'm always suspicious of crimp connections even ones that don't feel loose.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • JUGHNE
    JUGHNE Member Posts: 11,322

    P/S piping, strainer before each pump.

    2500 sq ft 2 story house, 637 EDR, CI rads, gravity system with 3" pipe.

    Strainers will pass just maybe tablespoon of black water and then clean.

    Have never seen more than 19* delta tee across boiler.

    But the lockout message, "outlet temp diff" when the probes read exactly the same values of say 106/106.

    Why not "boiler overheating" and then turn down flame until temp drops??

    I did bleed some air out of the 2nd floor rads, but can't imagine that air would be trapped in the basement piping at the boiler.

  • Jamie Hall
    Jamie Hall Member Posts: 25,453

    Not sure how those things operate, but — if the inlet and outlet temperatures read exactly, or almost exactly, the same, I'm going to say you have a sensor or computer issue — or no flow at all, in which case the temperature would rise very rapidly.

    Remember that the message "outlet temp diff" doesn't necessarily mean that the outlet temperature difference is too great… all it means is that it doesn't make sense.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 24,202
    https://forum.heatinghelp.com/discussion/comment/1825360#Comment_1825360

    did you pull the strainer out, or just the drain plug?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JUGHNE
    JUGHNE Member Posts: 11,322

    I have blow down valves on each and get full flow

  • JUGHNE
    JUGHNE Member Posts: 11,322

    This is a two story house that only utilizes the lower level for offices.

    I had in the past purposely not bled all air out of some 2nd floor rads to conserve heat. The rad would just stay warm on the bottom and this confirmed that water was moving thru each rad. I had read in Dan's books that some systems had no expansion tank, rather they would rely on the air head that was left in some 2nd floor rads.

    I did go upstairs to check the rads and found a couple that had a lot of air to bleed, more than I would have left on the initial start up some years ago.

    Since doing that I have not had a lockout. I am suspicious of this being a factor in the problem, but will see what the future holds.

    I can't see that air trapped in 2nd floor rads would affect the flow thru the boiler in the basement. The pressure stays at about 14 PSI cold and there is the 1 1/4" "state of the art" air eliminator before the system pump with the exp tank hanging below.

    The air eliminator does work as evidenced by passing air when refilling the boiler.

    Trying to not fire the parts cannon at this problem.

  • JUGHNE
    JUGHNE Member Posts: 11,322

    After the 2nd floor air bleeding on about 12/10/24 there has not been another lockout.

    It seems that microbubbles may have caused lack of flow at the boiler???

    But why that lock out code and not simply high temp overheating???

    bjohnhy

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