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LWCO resetting constantly

Rob_22-2 Member Posts: 10
LWCO problem

 Installed a new boiler during the summer at vacation home. Initial fire up was in September and all seemed OK. Was at the house over the weekend (Dec. 25th, 2010)  and started the boiler. All went well as we were bringing the house from 39 to 70 degrees. As you can imagine this took many hours. When the temp did reach 70 degrees the boiler shut down as expected. After going below the set point the boiler did not kick back in. I went down to the basement and observed the LWCO was blinking RED. OK, hmm, low water in boiler? Strange. Boiler pressure was at 16psi. Make up water supply is new and functioning. The LWCO is a TACO LTR0243U-1,with extended harness for a United Technologies controller on a WMcL CGS-6. The best I could figure was to reset the LWCO by unplugging the harness from the probe side. This reset the LWCO and the system was operational again. During the night this occurred again. Back downstairs again. This time I flipped the Emergency cutoff switch off, then on. System started right up again. In the morning I decided to check the radiators to see if I was getting any air pockets passing the LWCO. One rad needed some bleeding. Continued to run boiler OK, and it ran great all day. Again overnight I had to go downstairs and reset. Each time I reset the temp at the thermostat and stop the boiler this will occur. At this point all I can think of is;

1.        Faulty LWCO

2.        Faulty ground on electric panel

3.        Dirt in system

4.        Not enough water in system

5.        Waterlogged expansion tank

6.        Wrong leads from thermostat

7.       Probe threaded too far into pipe. (pipe is 1 1/4" black iron)

As we had to leave on Tuesday and did not have enough test equipment the condition basically will remain the same. I’m heading back down next week for an extended period and am hoping someone here may give me better insight as to how to correct this condition. Also as it stands I’m pretty sure to rule out 4,5 and 6.



  • tim smith
    tim smith Member Posts: 2,742
    Re: lwco tripping

    Make sure you have a good ground wire, pull probe and clean with fine steel wool. Make sure no teflon tape used on threads of probe as this can insulate ground path. Good luck
  • Rob_22-2
    Rob_22-2 Member Posts: 10
    Need teflon tape


    Yes, cleaning the probe is the next step of course, but the teflon tape is the manufacturers must. Threading compound is the no-no on the Taco LTR series LWCO devices. Odd, since if you look at other LWCO's it is Teflon that is the no-no. I think it's because the threading casing is of plastic and not metal that Teflon is allowed.


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