Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Crown Boiler/Honeywell L7224U Aquastat Problem

kinger62 Member Posts: 7
I posted this in Domestic Hot Water but I believe it is more suitable for this category.
I have a crown bd-74 boiler. Early in 2016 I replaced the aquastat with the L7224U and I've had no problems until now. My boiler is running at about 120deg. It is cycling on and off, and it is maintaining my home about about 63degF, regardless of how high I turn my thermostat. The display on the aquastat is showing STA 1. There are no error codes. This issue started a couple of days ago. Can someone tell me what this code means, and where to start troubleshooting? Thank you.


  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    What are all the settings? Maybe your well sensor isn't installed properly/not working.
  • northernboiler
    northernboiler Member Posts: 55
    "STA 1" indicates that you are in standby mode.
    Meaning the control with maintain the low limit temperature.
    That there is no call for heat to activate the control to turn the burner on to bring the temperature of the boiler to the high limit.

    Meaning that there is no call at TT

    I do not know if you have one zone or multiple zones or if you are using a zoning panel, etc.

    Assuming that you have only one zone, I would check that your thermostat is actually working, batteries maybe.

    If not that, try jumping the R & W wires at the thermostat and see if that turns the burner on.

    If not jump out T T on the aquastat.
    See if that makes it run.
  • kinger62
    kinger62 Member Posts: 7
    My BT is 114, my SP is 180, my HL is 180, HDF is 15. HR is off, DH is off. These are the figures I get if I push the "I" button and cycle through. Let me reiterate, this was installed two years ago and has been operating just fine, with good heat until last week.
    Thank you.
  • kinger62
    kinger62 Member Posts: 7
    Northernboiler, I jumped TT and the display went to STA 8 and the boiler fired. When I pulled the jumper it kicked off and went back to STA 1. What does this mean? Thank you for your help!
  • northernboiler
    northernboiler Member Posts: 55
    If you have an L7224 control, you should also have an "LL" setting.

    If you have an L7248 control, then it is possible that your sensor probe is not inserted fully or is not reading the temperature correctly (meaning it needs replacing)- as STEVEusaPA suggested.

    Or that the aquastat well inside the boiler has buildup on it preventing the sensor from correctly reading the water temperature.

    The last thing it could be is that the control is bad, not allowing the boiler to exceed 120.

    If you have gone through all of the settings , set them properly, tested the TT on the aquastat (jumping it out), and the tridicator gauge confirms the same temperature as the aquastat display, I would likely lean towards a bad aquastat control.

    If it were just the sensor, the temperature settings would most likely keep the burner running to a higher temperature.

    However, you should go through the other steps first.

    Btw, controls do go "bad" sometimes and can have a problems like the one you are experiencing.
    Without a plausible explanation.
  • northernboiler
    northernboiler Member Posts: 55
    STA 8 is "running "
    Normal operation

    Check thermostat or thermostat wiring.
  • northernboiler
    northernboiler Member Posts: 55
    And this may sound stupid, but, if you have a digital thermostat, try replacing the batteries.

    And if that doesn't work , jump the R & W wires at the thermostat.
  • mgdesrochers
    mgdesrochers Member Posts: 20
    We need a bit more information like @northernboiler mentioned. (Number of zones, zone valves or circulators, type of control if you are running multiple zones)
    You said you jumped TT and the control went to Sta8 and the boiler fired which would seem to indicate that the L7224U will fire the boiler on a call for heat.
    Have you jumped the wires at the thermostat? If you have a broken thermostat wire jumping the wires at the thermostat won't cause the boiler to run. Have you checked the thermostat batteries (if equipped) as suggested?
  • kinger62
    kinger62 Member Posts: 7
    I will go through these tests. If STA 8 is normal operation, should the display show this at all times, or bounce between STA 1 (standby) and STA 8, depending on whether the Thermostat is calling for heat?
    Thank you, everyone, for your help.
  • northernboiler
    northernboiler Member Posts: 55
    The STA will be at 8 when the burner is running
    Or when it has reached high limit temperature

    Otherwise it will read 1
  • kinger62
    kinger62 Member Posts: 7
    Well, I pulled all three thermostats and checked batteries, and they were all good. I replaced the thermostats and since then, my boiler has been operating normally. I don't know why, as I didn't replace any batteries. Maybe one had jarred loose? Anyway, I now have heat. Thank you everyone, for your advice and assistance!
  • rocky650penn
    rocky650penn Member Posts: 1
    my aquastat went out and was replace with l7224u 2 weeks ago. went on vacation for 7 days and I programmed thermostat for 60 degrees, came home house was 70. reset thermostat and same thing. ordered new thermostat and installed new one that is not programmable just turn dial to temp desired. same thing therm set at 60 and its 70 in house. any ideas? only oil furnace base board heat. separate hot water heater.
  • the_donut
    the_donut Member Posts: 374
    Check screw connection for rh. Try jumping r and c if connection is good a wire is tight.