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Lochinvar Knight KBN106, No 24 Voltage to Low Voltage Board

fieldguide
fieldguide Member Posts: 7
I have no 24v low voltage to Low Voltage Board (causing a Gas Pressure Switch Fault & Lock). I have replaced both boards, the main board twice, believing the first must have been defective. Wiring connections have been checked thoroughly numerous times. On recommendation of an online Lochinvar tech, I've also replaced the fan. I have 120v at the main board, but no 24v coming out at the output connector. I bypassed the main board and supplied 24v directly to the low voltage board. By doing this, the furnace doesn't lock out until it wants to fire and then locks out, because of course, I have shut off the natural gas since other monitoring systems are not receiving voltage. With voltage into the main board, but no low voltage coming out, are there other possibilities besides main board? Thanks for any feedback!
JohnNY

Comments

  • Ironman
    Ironman Member Posts: 7,350
    Did you check the low voltage fuse and transformer? The board doesn't create voltage; it receives it from the transformer.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    rick in Alaska
  • fieldguide
    fieldguide Member Posts: 7
    The KBN106 has a transformer dedicated to the gas valve only. It is working fine. 120 voltage is supplied directly to the main board which has its own voltage reduction and feeds the low voltage board. The fuses all check out. Thanks Ironman, other thoughts?
  • Ironman
    Ironman Member Posts: 7,350
    Is this wiring diagram correct?



    If so, check for 24v between the terminals circled in green.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • fieldguide
    fieldguide Member Posts: 7
    Similar, but variations. Mine was installed in 2010. I have no voltage at any of the connection board terminals, which includes the room thermostat and therefore have no room temp display. Since there are no gas pressure switches, there is a jumper wire connecting the terminals. I'm getting the Gas Pressure SW Fault and subsequent Lock since there is no voltage here along with all other 24 v terminals.
  • fieldguide
    fieldguide Member Posts: 7
    Got it running!! Thanks Ironman for putting me on the right track!! I'm new to this site, so are there ways to credit you for all your help? Thanks again!!
  • JohnNY
    JohnNY Member Posts: 3,226
    Very cool, @Ironman !
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    Ironman
  • Ironman
    Ironman Member Posts: 7,350
    So, what was the problem?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,549
    If you click on his post you can give feedback. Not that he needs more points :)
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    fieldguideSolid_Fuel_Man
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Awesome!
    He needs his own theme song, like walk up music for the closer in baseball!
    Right now I’m hearing Black Sabbath's Iron Man...
    Daah daaaah dah dah dah
    Dah dah dah dah dah dah dah
    Daaah dah dah
    steve
    Zmanfieldguide
  • fieldguide
    fieldguide Member Posts: 7
    @Ironman. I was studying my wire diagram after viewing the one you sent. I began tracing wires and realized something wasn't right. I discovered that 2 of the wire connectors were internally identical and therefore reversible. Mine were reversed! I was shocked that that was even possible! At any rate, the system is now good to go. Thanks for taking the time to help, you opened the way to solving the problem!
    IronmanAlan (California Radiant) Forbes
  • fieldguide
    fieldguide Member Posts: 7
    @Zman. Thanks for the help! (and friendly jibe :D)
  • fieldguide
    fieldguide Member Posts: 7
    @STEVEusaPA . Thanks for the laugh, you're hilarious!!