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Jumping TACO LTR0243 LWCO

dgkula Member Posts: 59
Hi, I had a Lochinvar Noble installed in May and the 12V LWCO failed last night. It has a four wire plug with red, black, white and green wires. I've not been able to get in contact with my plumber yet so am looking for advice on how to jump the device using a paper clip in the four wire plug. Any help on which two wires to connect to get the boiler running? I know it failed as the red light was flashing so following the manual I unplugged the four prong plug, waited 30 sec, plugged it back in and it fried out. Thx for any help.


  • Jamie Hall
    Jamie Hall Member Posts: 23,554
    Do NOT, under any circumstances, run a boiler without either a functioning low water cutoff or a sight gauge and a reliable person there watching it at all times. Not just every now and then, ALL THE TIME.

    So no, I won't tell you how to jump the devise..
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
    https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Taco - LTR0243T-1 - Install Instructions.pdf

    If you are smart enough to figure it out from this instruction sheet, then you are smart enough to know that you need to replace it with a working one ASAP

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Joe Mattiello
    Joe Mattiello Member Posts: 707
    contact Taco tech support for help; 401-942-8000, and ask for tech support. I can tell you, at times a probe can become fouled hindering the valves ability to work properly. You can remove it, wipe the probe with a TSP soap and reinstall it. Also, do not use a pipe tread tape, because the valve must be grounded. I do not recommend bypassing the safety portion of LWCO; repercussions could be severe. hopefully this was helpful
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • HomerJSmith
    HomerJSmith Member Posts: 2,479
    Frankly, you have to determine whether you really have a low water condition before you take any action. Look at the pressure gauge and see if it is at about 12-15 psi. If not, is the boiler water feed valve open? Correct any low water condition, FIRST.

    The Lochinvar Noble has Low water cutoff protection aside from the external LWCO, it wouldn't fire if you had a LW situation.

    If you have determined that water is present and the pressure is up, then you can proceed to the next step. Measure the voltage between the red and white wire it should be 24V ac. This gives you some indication of what needs to be done to determine where the problem lies. You really need a service technician to fully analyses the problem because it may be more than a failed LWCO which is why Jamie Hall and others are alarmed at operating the boiler.

    The assumption is you have a Low Water condition which would damage the boiler if fired, but the Lochinvar has a LWCO protection in which case the boiler wouldn't fire, anyway.

    A blinking RED led indicates a "Control failure. Lockout in Low Water
    ". The conductive probe may be coated with minerals if your boiler water is too hard and not seeing the water. Lots a things could be the cause. BUT...if you want to see which wires to jump, study the diagram.

  • GGross
    GGross Member Posts: 1,075

    Correct me if I am wrong but isn't the internal LWCO similar to other brands where it is just a pressure sensing device? I know for a fact the local inspectors in my area will not allow them installed without an external LWCO device, as they say technically it can flash to steam and the internal LWCO will not trip, allowing for the boiler to fire.
  • HomerJSmith
    HomerJSmith Member Posts: 2,479
    edited August 2022
    Yes, a separate LWCO is required. The internal pressure sensing device is boiler protection. It is not a substitute.