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HELP!!! HTP Elite 'water high temp' F00 lockout

I have had an HTP Elite boiler for 5 or 6 years and it has always worked fine. Last June I did some work on the floors in my house and had several radiators removed and then replaced once the work was done. The technician who re-installed the radiators and re-filled the system was completely incompetant (flooded the upstairs, etc.).
Ever since that re-installation, whenever I use a lot of hot water (the boiler also has a DHW zone), i get a 'water high temp' lockout. I have had several technicians come look at this, but most have had a very difficult time reaching tech support. Most recently, tech support walked a contractor through how to check for a bad sensor. It seems like that check was inconclusive. So tech support has recommended that the contractor change the main board on the boiler. I have this feeling that i'm going to pay for this repair and it isn't going to fix the problem. Is there any mechanical reason, or something to do with the pressure in the system that might cause this problem to happen. It seems strange to me that this only happens when i use a lot of hot water. One other detail, ever since the replacement of the radiators this past summer, there is an occasional knocking in the pipes. That was never there before.
Does anyone have any advice to offer? Or do I need to just proceed with the main board replacement.

Thanks in advance for any suggestions!
joe in chicago
(i also posted this in 'heating hell' by accident. sorry about that.


  • Ironman
    Ironman Member Posts: 7,379
    I doubt if the board is the problem.
    What's the limit for SWT set at?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mattmia2
    mattmia2 Member Posts: 9,754
    Possibly air keeping it from circulating right. Did someone close the caps on the automatic air vents pr something?

    Might try a factory reset too(after writing down all the parameters), their firmware may be a bit buggy. On my UFT I purged/flushed a zone a few times with the boiler software off but not AC line switched off and repeatedly tripping whatever was the lwco while doing that caused it to show no errors but also not generate a dhw call. A factory reset fixed that.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    Do you have several circulators or just one?

    Do you ever hear any air in the heating loops and have you gone around and purged each of the radiators? What is the operating pressure?
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • joebristol
    joebristol Member Posts: 2
    Hi All,
    Thank you very much for your responses. I'm not a contractor (just a homeowner), so I'm not sure how to answer every one of these questions. I've become more and more convinced though that the problem here is related to plumbing/pressure and not a defective boiler. The pressure in the system is set at 24PSI. there is a pump for the radiators and a separate one for the hot water loop, as well as a control valve for each. I dont actually hear any air in the lines that i'm aware of. i have bled all the radiators. I'm not sure how to check the setting for the hot water limit. Unfortunately, I havent been able to find a contractor in Chicago who is willing to try to troubleshoot the plumbing aspect of this problem. They all just want to call HTP and follow their instructions. The current idea is to replace the main circuit board in the boiler, but i am very skeptical that this will fix the problem.
    If anyone has any further suggestions, I am all ears. How do I check to see if someone closed the caps on the automatic air vents? Is a factory reset or a purge of the DHW zone something I could try to do myself?

    Thanks so much for your help!
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited December 2019
    24 PSI is way too high, even when the water is hot. Go into the programing and set the indirect temperature that the boiler puts out to the indirect tank to185 deg if you have a mixing valve on the indirect tank. If not, set the temp to 125 deg. You can also set the heating supply temp, too. If you have outdoor reset, make sure the heating curve is set to how you want your boiler to run.

    The Return Water Temperature Sensor can be checked with an ohm meter if you know the water temperature and compare it to the Resistance Chart, do the same for the indirect tank sensor.

    I would do this first, before replacing the board.

    Your manual will tell you how to access the programing

    1. Check circulator pump operation.2. If the circulator pump is running, ensure there is water in the system and that the water is moving through the system as intended. Ensure that all correct ball valves and or zone valves are open or closed as intended.3. Observe the temperature/pressure gauge. If the water is not too hot and this message is displayed, check the wiring to the water ECO sensor and repair if necessary. If the wiring is ok and this code is still present and the water is not excessively hot, replace the ECO sensor.
  • Timco
    Timco Member Posts: 3,040
    edited December 2019
    Hello! I’m sorry I haven’t been on here for a bit. I’m the technical support manger. Please email me at tim.white@htproducts.com and I’ll walk you through a few ideas I already have. Tim White
    Just a guy running some pipes.