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R7284U hard lockouts

I replaced an LED model control with an R7284U a year ago and it has worked fine until the last few days. Now when the call for heat is satisfied the burner shuts down normally, but display on control says hard lockout rather than standby like it should. Burner will not respond to a call for heat until it is reset. There are no operating conditions whichwould cause a lockout. Cad cell is running in low 200's, Fuel pressure is steady at 100 for the full run, and flame is stable.
When I simulate a high limit shut down and remove the call for heat the display goes to standby when the limit simulation is ended, and the burner starts with the next call for heat.
Only when the TT indicates the end of call for heat does the unit go into hard lockdown.


  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    edited January 2019
    That’s a new one.
    I’d just replace the control and see if it still does it. Make sure it’s properly grounded.
    I only say swap out because it shouldn’t go into hard lockout, just soft. So to me something is wrong with the control. Assuming it’s not locking out near the end of the call for heat.
    Also 200 ohms seems too lean. What’s the excess air on the combustion analysis?
  • StanInPa
    StanInPa Member Posts: 6
    It did the same thing last year at the end of the summer. High humidity in the basement with an active spring and busy sump pump. After about a dozen resets it dried out and performed flawlessly all winter. This year it ran normally for a couple of months and just now started with the lockouts.
    There's nothing happening at the end of the run cycle, I've watched it shut down.
    200 ohms on cad is because I'm running it on jet fuel (kerosene) with the draft doors fully closed, still leaner than optimum.
    HVACNUT Member Posts: 4,592
    I'm with @STEVEusaPA
    It seems like a bad primary.
    Did you go through the set up to see if anything changed? Sneaky Gremlins.
    What model burner? Valve on delay, valve off delay?
    TT configured on or off? (External jumper needed).
    Is the thermostat connected to TT on the primary?

    Boiler or furnace?
    What's the firing rate?
    You can get in the 400's with Kero and 0 smoke no doubt.
    What are the combustion test results?

    What burner manufacturer specs a burner for OEM or retrofit and sets the air at 0?
    If by chance we're talking about a low firing rate, (.60 GPH or less) something is wrong regardless of, or may be contributing to the lockout issue. Wrong setup, assembly depth, retention head, low fire baffle missing?

    Sorry if I seem curt. I'm still working on my first cup.
  • StanInPa
    StanInPa Member Posts: 6
    All setup still on initial default settings. Hot air furnace, dry contact t/stat across TT. Firing rate is .60GPH on Kero. I'm going to replace the control. It won't go to waste because I have a Miller monile home unit in the shop that I operate with an on-off snap switch. The flame out safety on this unit works perfectly, and I'll just add a jumper across TT, power up L1 and wire the snap switch to Limit and I will have the benefit of delayed fireing and flame out protection.
  • StanInPa
    StanInPa Member Posts: 6
    Correction on firing rate. ts .85gph
    HVACNUT Member Posts: 4,592
    What model furnace and burner?