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Weil Mclain WM97 - Taco LWCO fail every few months

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apanek01
apanek01 Member Posts: 10
The Taco electronic LWCO (model LTR0243T) fails every few months on my Weil Mclain WM97+ boiler. There is no low water condition in the boiler or air. Sometimes it fails with a red light, sometimes with an amber light. On occasion it blows the 3AMP fuse on the control panel. The only way I fix the issue is to replace the LWCO with a new one as it appears the LWCO electronics have been blown from something in the boiler itself.

Here is what has been done to try to determine root cause:

1) Replaced the transformer with new transformer
2) Replaced the front control panel with a brand new control panel
3) Installed a surge protector
4) Installed a RectorSeal VRM (Voltage Regulator Monitor) that cuts power to boiler in a surge or brown-out condition. I have set the low end of the cut-off to 115V and high end to 125V.

Has anyone experienced frequent failures on a Taco LWCO LTR0243T and determine root cause and how I might troubleshoot or override the Taco LWCO?

Thanks

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
    edited December 2021
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    I don't know but I would certainly contact Taco. They hang out on this forum occasionally and may respond. @Steve Thompson (Taco) or @Joe Mattiello
  • EJN451
    EJN451 Member Posts: 6
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    I have the same problem on the same(?) furnace (WM97+155). First fail was after 5 years of service, blew fuse. Second fail was 47months later, blew fuse. LTR0243 taco unit. Do not know is causing this, either. Both fails were during very cold weather, but no idea how this could be connected.
  • EJN451
    EJN451 Member Posts: 6
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    Erratum re above: 2nd fail was 23 months later (last night), not 47 moths later.
  • Jamie Hall
    Jamie Hall Member Posts: 23,436
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    It is a mistake to blame the boiler. It is an inanimate block of cast iron. You need to be looking either at the installation of the LWCO or in the other controls and power circuits.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
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    Why not call Taco just replacing the controls with nothing found just invites another failure
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited January 2022
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    It is a mistake to blame the boiler. It is an inanimate block of cast iron. You need to be looking either at the installation of the LWCO or in the other controls and power circuits.

    Jamie, I believe the LWCO is a factory installed part on the WM97



    So .... Yea ... Blame the boiler ... all the wires, controls, tubes, and other parts (like the block) are all part of the boiler. There is something in there that is causing this failure, whether it be a bad connector, poor location design, or something exclusive to that particular boiler. Without locating that cause, than I agree with @EBEBRATT-Ed

    Edit: I like to think outside of the box. what if you extended the wire to a location outside of the boiler jacket. Can you install the LWCO on a fitting installed on the connecting near boiler piping? That would put the LWCO in a different temperature zone... Just a thought

    Edward Young Retired

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

  • Jamie Hall
    Jamie Hall Member Posts: 23,436
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    It may be a factory installed part, @EdTheHeaterMan , but it is not a Weil-McLain part -- any more than the Firestones on you new Ford Exploder are a Ford part. And blaming the Ford for the flat Firestone will not get you very far.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EdTheHeaterMan
  • JUGHNE
    JUGHNE Member Posts: 11,075
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    But if the LWCO is married to a control board that powers it, there could be something bad in the marriage...so to speak. IMO

    For instance my Lochinvar factory LWCO plugs into the main control board so your read out will tell you of the reason for that particular shut down.
    EdTheHeaterManknotgrumpy
  • wmgeorge
    wmgeorge Member Posts: 222
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    Speaking as an Electrician, find one that knows commercial - industrial not your typical house Romex runner. Tell them the issue and check the building ground to service panel and boiler ground connections. I have seen strange problems traced back to a corroded ground connection.
    Old retired Commercial HVAC/R guy in Iowa. Master electrician.
    EdTheHeaterMan
  • Lance
    Lance Member Posts: 271
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    More fodder for your mill. I love a mystery as long as its not my heat system. Grounding is important. Verify all grounding of boiler is good. From The power supply to control boards. Follow Taco install instructions exactly. it says 2-3 wraps of tape dope, it means just that. Water chemistry is probably not an issue, but will it be a factor? The circuit must be measured. Is a heat anticipator involved at the stat and is it set properly? What is the voltage and amperage along the circuits between the control and the board? May require splicing in a test cord. Your clue is the 3 amp fuse blowing. This means the fuse did its job and you need to find the path and the condition that creates excess current. Divide and conquer. Isolate the thermostat loop. Measure the stat circuit disconnected and check for a voltage drop. Compare T T without the stat circuit and with the stat circuit in series. A possible partial short may be occurring due to poor insulation of wires or even a staple in a wire. Never jumper TT with the stat in the circuit to test the circuit. It can change the circuit from a series to a parallel loop. Hint: sometimes the tech for this job is an HVAC tech. He has the tools and understands control circuits. Good luck.
  • apanek01
    apanek01 Member Posts: 10
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    @EdTheHeaterMan nice to meet you and finally great to hear someone with same issue -- although I don't wish this upon anyone!

    You are correct LWCO is factory installed and tied to the control board. I have used Weil McClain and Taco branded LWCO and they all fail the same in this boiler and same specs - just the Weil McClain branded LWCO is double the price so I switched to the Taco's. I have called Weil McClain and they offer no help with the Weil McClain LWCO installed - they say they have not seen this issue before. Taco says they have not seen this issue before either, but did confirm their LWCO is compatible with this boiler -- it is exactly the same as the Weil McClain branded LWCO.

    Taco said might be something with the blower motor or gas valve sending a surge as it on the same low voltage leg as the LWCO. Taco took 2 of my failed LWCO to send them out for diagnostic, but they never get back to me -- they just keep telling me they are out and haven't heard back from manufacture.

    You have the 155 model. There is an article about a MELTED BURNNER GASKET issue that only affects the WM97+ 155 regarding ground and the gas valve. Have you seen this or done the replacement?

    https://www.weil-mclain.com/download/file/fid/3021

    Are you using the integrated DHW tank that mounts to the bottom of the unit? If you are not, please be aware that the power leads sit on the bottom frame of the boiler in the left and right corner and they are not capped or protected! You will see them just sitting their when you take the front control panel off. I wrapped the DHW leads with electrical tape and zipped tied them off the frame in case they are shorting on the frame or getting wet as you get a little water when replacing the LWCO since it is in the boiler -- bad design!

    I am also planning to install this inline to hopefully protect the LWCO

    https://www.amazon.com/POP3-Lil-Popper-Fuse-Tester/dp/B07FWFZCSF/ref=sr_1_1?crid=1CFXKV8262ACU&keywords=3+amp+li'l+popper&qid=1643585811&sprefix=3+amp+li'l+popper,aps,68&sr=8-1





    Daveinscranton
  • Tim_D
    Tim_D Member Posts: 128
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    If you are blowing the 24vac onboard fuse you have a short in one of the 24vac circuits which includes the LWCO. If replacing the LWCO corrects the issue for a period of time then that is the place to start looking. I have seen a few where the molex plug was 180 degrees out which causes a short.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited January 2022
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    It may be a factory installed part, @EdTheHeaterMan , but it is not a Weil-McLain part -- any more than the Firestones on you new Ford Exploder are a Ford part. And blaming the Ford for the flat Firestone will not get you very far.

    LTR0243T is a Weil Mclain Part number is 571-100-006

    So I believe it is a Weil Mclain Problem to resolve. But I see Your point. every part on a WM boiler is not manufactured at the foundry. But when your FORD fuel injector fails, you don't call Bosch or Detroit or the injector manufacturers... You go to the FORD dealer.

    And I believe you see my point. (you are one of the contributors that I look up to here) I contend this is a Weil Mclain Tech Support issue. But I am also of the opinion that WM probably won't be very helpful. It is past the part warranty coverage of 1 year.

    Edward Young Retired

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

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
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    apanek01 said:

    @EdTheHeaterMan nice to meet you and finally great to hear someone with same issue -- although I don't wish this upon anyone!

    I'm not an owner of this boiler, I am a retired HVAC contractor that worked on many different WM boilers. I may have even installed one on a radiant heat job that I was assisting the plumber of record on the job. I think there was a separate DHW source on the job. I have mixed feelings on WM as a manufacturer. I became friendly with many of the WM employees at my local factory warehouse in Pennsauken, NJ in years past. But as a whole, they are not as customer friendly as some other manufacturers.

    I suggested that you relocate the LWCO outside of the Jacket. Put it on a pipe that is above the exterior of the boiler and just get a longer wire to connect it to the control board. You can put a plug in the hole (3/4" tapping) where the old LWCO is located. Just make sure the location you choose will not be subject to air lock of any kind. this means there mist be water at the location ALWAYS. This will remove the possibility that the area inside the jacket is overheating and causing the problem. Im not saying that is the problem, Im saying that this adjustment will rule out overheating or over-humidity that may be in that location.

    Just a thought. If you post a picture of your system from far enough away to see the near boiler piping above and below the boiler, I may be able to suggest a convenient location.

    Edward Young Retired

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

  • wmgeorge
    wmgeorge Member Posts: 222
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    If it was a product issue, would it not be failing for others? Looks to be a job specific issue. So no need to re-design the wheel.
    Old retired Commercial HVAC/R guy in Iowa. Master electrician.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited February 2022
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    wmgeorge said:

    If it was a product issue, would it not be failing for others? Looks to be a job specific issue. So no need to re-design the wheel.

    What is your suggestion? If the factory provided part and the identical aftermarket part are failing prematurely, do you try something different or just keep doing the same thing. Perhaps there is an electric amperage or voltage issue and that part is the weakest link in the entire house. It sounds like the OP has been trying to eliminate each item by the process of elimination. So far...

    1) Replaced the transformer with new transformer
    2) Replaced the front control panel with a brand new control panel
    3) Installed a surge protector
    4) Installed a RectorSeal VRM (Voltage Regulator Monitor) that cuts power to boiler in a surge or brown-out condition. I have set the low end of the cut-off to 115V and high end to 125V.

    I did not see move LWCO location on their list, so I made that suggestion... Here is another

    There are different manufacturers of the same device. GuardDog RB-24E uses the same basic footprint and same wire plug connector. Maybe that will resolve. There are so many ways to go here.

    I have been in the business for over 40 years. I have found that changing contractors is the worst way to resolve an issue.
    The new guy needs to start from scratch and possible try the same thing the original contractor did. by sticking with me, a customer gets my experience of all my customers and also the experience I have on their system. I already know what didn't work for the last 2 years, 3 years or more. When I stick with a problem like this, I'm determined to resolve it.

    OFF TOPIC but an example of thinking outside the box.
    There is a very interesting and unusual fix I was able to make for a customer that was having odor then after repairing the odor problem, there was a nuisance lockout issue that lasted for 3 years. Here is the post I made about that: https://forum.heatinghelp.com/discussion/comment/1651498#Comment_1651498

    Edward Young Retired

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

  • Jamie Hall
    Jamie Hall Member Posts: 23,436
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    True, you are talking about a Weil-McClain supplied part. As has been noted, an essentially identical part is sold under other trade names.

    However.

    The fundamental problem is that you have had identical problems several times with the same part. While it is tempting to continue to blame the part, almost always when a replacement part fails in the same way as a previous part -- it's not the part. It's something else. Keep looking.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EdTheHeaterMan
  • apanek01
    apanek01 Member Posts: 10
    edited February 2022
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    @EdTheHeaterMan I appreciate the suggestion, but if the LWCO had an issue located inside the boiler as root cause I would suspect to see more issues reported? My install is a condo / commercial building install so it also has a external LWCO installed by code. I was concerned at one point that amount of heat build up inside the boiler might be causing premature failure of the LWCO. But others with the WM97+ boilers are running fine as you are the first person I have stumbled upon that has a customer with same issue as I have.

    BTW I looked up the GuardDog RB-24E that you suggested to install outside the boiler. This has a lower ambient max temp rating of 120 degrees. The Hydrolevel SafeGuard 1100 has a 170 degree max rating and the Taco has a 150 degree ambient max rating if you are concerned about heat level.

    Maybe a different LWCO model would be able to survive the surge, but that would not be fixing the root cause and I have tried a few different models with same result.

    Here is what I think might be a better work-around until root cause can be isolated. Maybe try this with your customer for the WM97 155 with same issue. I am going to install a breaker inline of the LWCO to protect and isolate. I did not want to cut the existing wiring harness to do this and purchased a extension cable:

    StarTech.com Power Cable
    8in ATX12V 4 Pin P4 CPU Power Extension Cable
    Model: ATXP4EXT
    https://www.amazon.com/StarTech-com-ATX12V-Power-Extension-Cable/dp/B000O7WFHA/ref=sr_1_1?crid=295XW1ILW0IIR&keywords=ATXP4EXT&qid=1643711540&sprefix=atxp4ext,aps,73&sr=8-1

    and

    ESP Li'L Popper - 3 AMP Control Circuit Breaker
    https://www.amazon.com/Amp-Circuit-Breaker-Push-Button/dp/B0078S7N66/ref=sr_1_7?crid=NUCRADLFKXM5&keywords=lil+popper+3+and+5+amp&qid=1643711644&sprefix=lil+popper+,aps,70&sr=8-7



  • apanek01
    apanek01 Member Posts: 10
    edited February 2022
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    @Tim_D I have on order a new wiring harness (backordered until March 22). I have gone through all the molex connections and traced the wiring harness and don't see any visible issues -- but I purchased a new harness anyway to just rule it out. Reminds me of an issue with an old car misfiring and the mechanic and I spent months trying to figure it out - replaced ignition coils, spark plugs and wires. We finally isolated to the cars wiring harness. Replaced the main wiring hardness and the misfiring resolved!

    So Taco had suggested to look at the blower motor and gas valve as a possible root cause of sending a spike through the low voltage side as the LWCO shares the same leg. Any suggestions on how I might test these to see if it these are sending a surge back through the system? I think I would need some type of monitor and logger for this as this could go for months before the next issue occurs.
  • tim smith
    tim smith Member Posts: 2,765
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    What's your total amp draw on the 24v circuit when running. Check with priority dhw running then with all heat zones running separately. Are you well under the 3 amp rated fuse? 2nd, make sure none of the control wiring in boiler is touching pipes, look close for slight wear/melting of insulation where they may have been touching. Good luck.

    apanek01
  • EJN451
    EJN451 Member Posts: 6
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    I just want to point out that the taco unit all by itself presents a short-circuit across the 24VAC leads when it fails, hence the fuse blowing has nothing to do with other loads on the 3A buss. I have experience in semiconductor development and the failure mode does look like that due to a transient over-voltage into the unit, as some have suggested. I may de-pot the original (failed) unit to see exactly what failed, but it looks to me like it is the input diode bridge, as I can't imagine any down-stream (internal) component causing such a hard fail (effectively less than 1 Ohm load). I like the idea of the blower or valve causing transients. My original blower failed after 3years of service (tachometer failure), so maybe it too was a victim of transients, perhaps from the gas-valve solenoid? Thanks to all for the ideas and comments.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited February 2022
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    apanek01 said:

    @EdTheHeaterMan I appreciate the suggestion, but if the LWCO had an issue located inside the boiler as root cause I would suspect to see more issues reported? My install is a condo / commercial building install so it also has a external LWCO installed by code.

    If there is a LWCO located outside the boiler jacket, than I would just eliminate the internal LWCO and connect the wire to the exterior control. If the exterior LWCO controller does not use the same connector, then I would just jumper the interior control and rely on the exterior one. You certainly don't need 2 LWCO controls. Remember that all boilers are not equipped with internal LWCO controls. The code you refer to requires 1 LWCO and the inspector wants it outside the boiler where he can see it. A good Installer with a good rapport with the plumbing inspector could have made the case the the boiler has a LWCO and that one is better designed to protect the boiler based on the location. But that assumes the plumbing inspector has a half a brain.

    As far as other boilers like yours having your particular problem... I have found that "NO TWO SYSTEMS ARE IDENTICAL" You will need to find the problem that is unique to your system, or find a work around.

    Edward Young Retired

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

  • Tim_D
    Tim_D Member Posts: 128
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    I doubt that the gas valve or blower are sending a spike.
  • johnkingston386
    johnkingston386 Member Posts: 2
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    I'm having the exact same problem with a WM97+ boiler every month I have to replace the LWCO, did anyone have a solution to the problem. The company WM said it was the cutout an to use a Hydrolevel LWCO instead but I don't think that is the issue.
  • apanek
    apanek Member Posts: 2
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    @johnkingston386 I replaced my LWCO with the Hydrolevel 1100M in Feb as I had another failure. I switched from Taco to HydroLevel just because it was cheaper. It has not failed yet which seems a bit odd as I would have expected to fail in March or April based on previous history. But this has happen before were I install a new Taco and sometime seems to last longer than others. Now that I am out of the heating system and it is only heating hot water, I don't usually see LWCO failures in the non heating months. I would expect this one to fail in October or November when the heating season starts again.

    I will post back here if the Hydrolevel LWCO fails. Let me know how you make out as I am very interested in solving this very "expensive" mystery!

  • johnkingston386
    johnkingston386 Member Posts: 2
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    Yes I will. I'm wondering if I should buy 6 LWCO for next season.
  • apanek
    apanek Member Posts: 2
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    I keep at least 3 LWCO in my stock at all times.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited May 2022
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    Just a thought. Place a LWCO on a different part of the system. Wire it to a different power source. Use only the dry contacts, isolated from the power source, to break the burner circuit using the auxiliary auto limit of the WM 97+ low voltage terminal board as shown

    The final step would be to take the connector to the factory LWCO and determine what wires need to be jumped to complete the burner circuit.

    I believe it is B4 and B12 on the plug but I can't be sure. Since many of you have these wires and these controls in your inventory, perhaps others can verify this. I do know that if you purchase the after market LWCO with the wiring harness, it is the two yellow wires on the aftermarket controls that need to be jumped. But that does not help on the Weil McLain control and wiring because the colors on the factory wiring are different. I believe that on the Molex plug, the wires marked 1 & 2 are 24V. power to the device, 3 & 4 are the switch dry contacts. Those numbers are very hard to find on the plug though.


    I'm not sure that this is correct so verify before you make the final connection

    Edward Young Retired

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

  • EJN451
    EJN451 Member Posts: 6
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    I just had my 3rd failure this week, just 6 months after the previous. This was the first mid-summer incident, perhaps contradicting the idea I had that it would be winter-time fails due the the much higher frequency of starting/stopping elements of the furnace.

    The frequency of failure is increasing with time. Original failure 42months, second 23months, third (lastest) 6 moths. On this latest replacement, I had added a 22 Ohm resistor in series with a 1A fuse in the 24VAC line to the taco on the new replacement last March. This time the resistor was crisped nicely and the 1A fuse blown, leaving the control board running (protected the 3A onboard fuse). Again, the 24VAC input to the now dead taco is essentially a short-circuit, just like the other two failures, indicating some kind of over-voltage incident. I did dissect the first failing unit to find that the input rectifier bridge diodes (2 of 4) where shorted, as expected, again indicating over-voltage. I had hoped that the 22Ohm series resistor might allow those diodes to survive a mild over-voltage transient, but obviously this was not the case! The main control board is now (for the first time) acting a bit odd. I will no longer let me enter the contractor mode, though otherwise seems to function normally.

    I made a new observation over the last 6 months; the unit had been logging Max Rate of T-rise errors every few weeks, which self-corrected, for well over a year now. But lately when examining the failure log the temperatures saved were now sometimes jumping in value as I watched them - not possible for a 'saved' value. It also began to throw some lwco fails (rarely, and not associated with the T-rise error events) that self-corrected. Made me think the control board is either getting messed up now by some kind of transients, or the board itself was going bad. I do have a new replacement board to try when I am ready to do so. Maybe my board is creating the transients (don't know how)?

    I will install a dedicated 24VAC transformer next, which should decouple the taco from the other elements, presumably still leave the root cause in place. At least this give me some time try to find the source of over-voltage. Will update as learn more.
  • EJN451
    EJN451 Member Posts: 6
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    Correction to one point, above. I was wrong about the Control Board acting up once I powered down for a few minutes and repowered. It appears to be back to normal now, in contractor mode. The error log was interesting showing the two consecutive lwco faults (looks like when it finally blew the fuse I added). There was a prior lwco error two days earlier. Of course the water was not low at any time. I am setting up a transient recorder in the hope of catching the culprit in action.
  • 109A_5
    109A_5 Member Posts: 1,387
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    @EJN451, you seen to have some Electrical / Electronic expertise. If the equipment grounding bonding between the Boiler's electrical system and to the pipe that the LWCO is mounted to is inadequate, a Voltage could build up exceeding the bridge rectifiers specifications causing their failure. Maybe the pipes are at one potential (Domestic cold water pipe connection) and the AC power feed ground wire is at another and the LWCO is in the middle of (or the path of) the difference causing damage to it.

    If you are quite convinced the 24 VAC has serious transient Voltages, as you mentioned a separate transformer may resolve it (but it should not have to come to that).

    A 24 VAC over-voltage clamp circuit. One version for testing.


    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • clammy
    clammy Member Posts: 3,113
    edited July 2022
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    I haven’t work on said boiler but I would believe that after the second electronic hot water lwco failed I would have done the following
    1 remove existing 24 volt lwco and install a line voltage and just use the contacts to the boilers terminal strip .
    Over the years I ve ran into issue w factory installed 24 volt lwco especially on hot water boiler . I feel if your gonna use a 24 volt model then wire in a seperate transformer for it . Even though it factory wired and installed there other loads on the transformer and as soon as they get weak it seems the low voltage lwco fail . I have always just used a 110 volt lwco and mostly taco and have rarely had to replace them unless terrible water chemistry again rarely seen on hot water boilers.
    I highly doubt the boiler manafacture is going to admit there wrong they ll have you chase your tail . Just think about it most commercial boiler use line voltage controls and rarely have these issues this is why I use line voltage lwco and rarely have issues and if your extremely worried the add a surge protector but I feel the issue lie else where and switching to line voltage would surely stop any issue w suppling the lwco w the correct voltage . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
    heatdoc1EdTheHeaterManSuperTechTom444
  • dgkula
    dgkula Member Posts: 59
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    @apanek01 did you ever figure out what was happening?

    Charlie from WMass installed a new Lochinvar Noble to replace my failed Buderus boiler in May 2022. We had the Taco LWCO fail in August 2022 and the replacement just failed today New Years Day 2023. 3 months for the first one and 4 months for the second one. Charlie is on his way out now to replace it - wanted to see if anyone had any idea why these are failing?
  • dgkula
    dgkula Member Posts: 59
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    @Joe Mattiello any thoughts? This is my second failed Taco LWCO in 7 months.
  • dgkula
    dgkula Member Posts: 59
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    and BTW in both cases I definitely do not have a low water condition.
  • EJN451
    EJN451 Member Posts: 6
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    My latest taco lwco is still running (last one failed July 2022). I started fresh on my system by tracing every single ground connection from the WM97+ to the house electrical panel entrance. They all appeared to be good, but I did not like how three were done (ground loops) and improved those. I do not believe these were a problem, however.
    I did have a new thought, as I stared at the WM 97+. The high-voltage electrical wire in my installation ran freely from the electronics board to the igniter on top of the boiler, passing pretty close (inches) by the wiring harness from the electronics board to the LWCO. Just how close these two cables were to each other was not well controlled, and my previous attempt to isolate the LWCO lines from the electronics board added more wiring nearby the HV cable run. So, my latest theory became that the transient high-voltage spikes induced large currents in the LWCO cabling (there is no way an actual arc could occur) and each time I replaced the (failed) LWCO, the proximity was changing randomly (since I paid no attention to it). Last summer I re-routed the HV cable through a large loop on the front of the boiler (looked like maybe that was the intent) and routed the LWCO harness as far away as possible. Have made it to February so far, but not much of a test. At least I like this theory better than my previous ideas. Were it correct, adding the separate 24VAC transformer might not have worked, as I likely would have had a similar routing proximity issue. I can see where the line-voltage version would be more immune to such a coupling. I'll report back on my next LWCO fail, or the 12-month mark, whichever comes first.
  • 109A_5
    109A_5 Member Posts: 1,387
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    Hello @apanek01,
    apanek01 said:

    Sometimes it fails with a red light, sometimes with an amber light. On occasion it blows the 3AMP fuse on the control panel.

    It is interesting the internal failures often seem different (unless the microcontroller is being zapped). Keeping the High Voltage wire away from all other wires can't hurt, but I'm not confident that has been the problem. Have any of the failed units been looked at to determine what exactly failed ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • SteveSan
    SteveSan Member Posts: 235
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    @EJN451 Please see below for our LWCO wiring to the unit.

    1. Run the LTR cable as far as possible away from other wiring and controls that use or generate high voltage or high current. This includes circulators, ignition systems, inducers, etc. and their wiring.
    2. Avoid looping the LTR cable. Loops can create an antenna that can increase susceptibility to noise.
    3. Avoid running the LTR cable parallel to other control wiring or power wiring.
    Parallel conductors are more easily induced with noise from other wiring.
    4. If other power wiring must be crossed, ensure the LTR cable only crosses at right angles.

    If you have any questions, please give Taco Technical Services a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000
  • Tom444
    Tom444 Member Posts: 1
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    i also encountered this issue. WM97+ orig. taco lwco lasted 8yrs. i ordered 1 online from supply house,went thru all the troubleshooting in previous post's.bought multiple shelf units all failed in 3 months or so. long story short, WM parts are specifically engineered for their brand ,as i learned the hard way trying to save a buck.i ordered their part # and problem solved.
  • murphpipes
    murphpipes Member Posts: 2
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    What’s up guys

    i am just getting home from a nice emergency boiler swap out followed by a late night service call that I didn’t completely resolve 

    im sure a lot of you can sympathize 😂

    So the wm 97+ 155 apparently has some infamy with these low water cut offs. The part was discontinued from the looks of it and renumbered. 

    I saw some posted that they had different lights and different failures on the Lwco some red some amber and some blown fuses as well. 

    What I’ve got going on is no lights at all and the display is still lit up telling me the low water circuit is open.  So I verified water is in the boiler and that I had continuity in the harness - condemned the sensor. but. it also looks as though others have also replaced the board which I know is common in these mod con boilers. I guess what I’m wondering is how did you decide to add a transformer and inline fuse and new control board if you’ve never witnessed a spike or surge? Was Just finding a blown fuse enough to justify that?  I guess im thinking if I put another lwco in and this happens again - before I put another one in or started modifying the design of the system and adding things like external lwco and jumpering out the factory. I Would probabaly rather replace the whole damn boiler.  A couple trips out on emergency rates basically justifies the cost.  I do always tend to swan dive into trying to fix things that probably are better off replaced but I think that’s more for myself then it is the customer. Haha 😂. Anybody ever figure this ghost power surge issue ?