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TriangleTube Prestige Solo LWCO Failure (b26 error) and solution

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zak
zak Member Posts: 2
I am posting this for others to learn from what I found out.

LWCO (Low Water Cutoff) device. This is a safety device that shuts off the boiler (soft lockout and b26 error code) if the water level in the boiler gets too low. However, it doesn’t actually measure the water level in the boiler. Instead it measures pressure, and if the pressure gets below 10 psi, the assumption is that this would be due to a leak and a resulting low water level in the boiler. So, when the pressure is above 10 psi the LWCO device contacts close and the boiler functions normally.

If your system pressure is above 10 psi, you shouldn’t be getting a b26 error. If you are, there is a good chance that your LWCO device has failed. You can check it with a multimeter by verifying continuity across the two terminals with it installed and system pressure above 10 psi. Another way to check it is to remove the two wires connected to it, and connect those two wires together. This will bypass the sensor and trick the boiler into thinking the pressure is above 10 psi. Your boiler should now run once the soft lockout clears. Only do this for troubleshooting, not to continuously run your boiler since you now don’t have the LWCO safety protection. Without continuity above 10 psi, your LWCO device needs to be replaced or “refurbished”.

In the 10 years that I have had my TriangleTube Prestige Solo 250 boiler, the only issues that I have had are multiple LWCO failures. For the first 2 times, I simply replaced the sensor. Since you have to depressurize and then re-pressurize the system to do this, it became a project to replace the sensor. I decided to modify my boiler setup so I wouldn’t need to depressurize the system to make the swap. As you can see in the first picture, I removed the LWCO device and added an elbow and shutoff valve prior to the LWCO. With this setup, I can simply close the valve and remove the LWCO as necessary. I also added in a more accurate pressure gage to verify the system pressure near the LWCO, and a bicycle type Shrader valve at the top to be able to bleed the air out of the riser if necessary.


Before modifying my boiler, I didn’t want to try to “refurbish” my used LWCO sensors because of the hassle with replacing them. After I modified it, I decided to try to fix the failing ones since it would be easy to replace them if they failed sooner than a new one.

In the next picture, you can see that the LWCO device unscrews apart. One part has a brass housing with a rubber diaphragm inside. The other part has the plastic housing with the protruding button that normally rests against the rubber diaphragm. With pressure above 10 psi, the rubber diaphragm pushes against the button which closes the internal contacts. The plastic housing can also be pried off to access the internal contacts. This is the trickiest part. I broke the housing on the first one I tried, rendering it useless. The two silver bumps are the contacts that mate against the silver disc. The spring keeps them apart until the pressure exceeds 10 psi. On one of mine, the contacts had blackened and I cleaned them to make better contact. This might not be necessary. The rubber diaphragm can be removed from the brass housing and cleaned. There isn’t any glue holding it in place, but it tends to stick. I used a flat dowel to push it out so as not to puncture it.


It’s hard to tell what causes the device to fail. I’ve gotten different theories from different smart people. Those are: (1) the button sticks, (2) the rubber diaphragm gets gunked up and isn’t able to push hard enough against the button, and (3) the contacts get blackened and fail to make contact. I just clean it all and add a dab of WD40 to the edge of the button where it rubs against the plastic housing. I recommend skipping removing the plastic housing if it doesn’t come off easily for you, unless the other two don’t fix it.

As a final thought, I originally installed the Shrader valve to bleed the air out of the riser. After thinking about it and discussing it with others, I might use the valve to ADD air into the riser so that the diaphragm has air against it instead of water. That might keep it from getting gunked up and last longer. Although air compresses more than water, once the system is pressurized, there shouldn’t be any difference between air and water pushing against the diaphragm. I wouldn’t recommend this unless you have an air bleeder in your system in case you add too much air and it gets below the riser and into the system.
masterhvac

Comments

  • Alan (California Radiant) Forbes
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    Thank you for your post.

    It's interesting that you're having so much trouble with your LWCO. The problems I've had with Prestige Solo boilers are varied and vexing, but never with the LWCO.

    That's a great way to set up the device, but if it keeps on happening, I'd be installing a different brand.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    BillyO
  • Zman
    Zman Member Posts: 7,573
    edited March 2020
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    I would check your water quality. That many failures is unusual.
    I would also recommended pulling the handle off the ball valve. It would be way too easy for someone to override a critical safety component.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    kcoppDan Foley
  • Zman
    Zman Member Posts: 7,573
    edited March 2020
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    @Erin Holohan Haskell
    Why are the disagree and off topic commentators not shown?
    This is a classic example of someone just leaving random negative feedback when receiving constructive advice.
    @zak is it you?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Alan (California Radiant) ForbesJUGHNE
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,326
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    @Zman, if you're on a desktop computer you can hover over the reaction to see who made it. We'll look into making this feature more mobile friendly. Thanks for the feedback.

    President
    HeatingHelp.com

  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,326
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    @Zman, I've made some edits. Now, on both mobile and desktop, the avatar (profile image) of each person who reacted will appear above the reactions panel with the icon of the reaction on top of it. You can click on the avatar to see the person's username. Please let me know if this works for you all. Thanks.

    President
    HeatingHelp.com

  • zak
    zak Member Posts: 2
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    Zman, that's a good idea about removing the handle. I'll do that, although I'm the only one who gets near the boiler. We used tap water in my original system, but when I upgraded to the Prestige Solo we cycled in balanced/purified water from the grocery store and added Pro-Tek 922 treatment. I'll admit, I haven't changed it since, but it's a closed system and I don't introduce tap water to repressurize it. Also, I'm not sure what you are referring to about the "random negative feedback". This is all I have posted.
  • DZoro
    DZoro Member Posts: 1,048
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    I have seen this in the older TT's. Contacts get dirty, but doesn't seem to be a reoccurring problem.
    D
  • Zman
    Zman Member Posts: 7,573
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    @Erin Holohan Haskell
    I a running windows 10 pro and chrome.
    When someone reacts with off topic or disagree, it does not tell you who. With other comments it does.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,326
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    @Zman I'll send you a PM so we can troubleshoot.

    President
    HeatingHelp.com

  • Zman
    Zman Member Posts: 7,573
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    @zak
    Glad to hear it was not you. It sounds like a glitch with the site.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Alan (California Radiant) Forbes
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    Zman said:

    @Erin Holohan Haskell
    Why are the disagree and off topic commentators not shown?
    This is a classic example of someone just leaving random negative feedback when receiving constructive advice.
    @zak is it you?

    I think someone was having a bad day.

    And I don't think the person's identity should be shown for "Off Topic" and "Disagree" comments. It would lead to more bickering and bad feelings.

    Yes, it hurts when you've shared your professional opinion and some low hanger comes along and clicks "Off Topic", but they walk among us, no?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    kcopp
  • Zman
    Zman Member Posts: 7,573
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    I like to know who it is because it helps me determine whether I should re evaluate my position on the topic. I have had negative feedback from someone with only a few post and have simply ignored it. If it comes from a respected regular on the site, I wonder if I got it right. Sometimes asking for clarification.

    One of the issues with this online stuff is that people tend to hide behind the anonymity. People would behave better online if they were a little more accountable.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    DZoro
  • DZoro
    DZoro Member Posts: 1,048
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    I agree, it's good to have a discussion on all the comments good, and the not so much good comments. That's how we all learn.
    D
    Zman