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LWCO issues

Having trouble with my steam boiler.
Mcdonnell & Miller LWCO is not flushing properly. Seems to be clogged as minimal to no water coming out. Can it be cleaned out, or does it need to be replaced? Please advise.

From Dan's book, I know this is a potentially serious situation, but I'm having trouble finding someone well versed in steam heat to come out and look at this.
I left a message for Steam Whisperer. I know Dave is a consummate steam pro, so I'm waiting to hear back, but in the meantime, is there anyone else in Chicagoland area well versed in steam heat?
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Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,280
    edited November 16
    It can bel cleaned. Try gently pushing a stick up in the valve when opened. this may break loose some of the sludge and allow for faster flow during flushing. CAUTION THE WATER CAN BE SCALDING HOT. Let the boiler cool down to try this procedure

    Not sure if you have this one however the maintenance is the same on all mechanical LWCO devices. The following is from the #67 McDonald & Miller
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org

  • rystephan
    rystephan Member Posts: 19
    Thank you, EdTheHeaterMan, for the prompt reply!
    Yes, I have a M&M #67 and those are the directions I follow for maintenance, but I haven't been able to blow it down. When I fully open the blow down valve, it makes some knocking noises and no water comes out.

    To try your suggestion, where do I push the stick up into the valve? My discharge piping from the LWCO is not a straight shot. (has two elbows) I'll try to send pic.
    You said to let the boiler cool off before trying this procedure. Should I open the valve then (yellow lever ball valve) when the burners are off?
  • rystephan
    rystephan Member Posts: 19


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,280
    The valve with the yellow handle is a ball valve. You need to stick something in that valve when it is open. Be careful because your pencil will touch the float mechanism and you do not want to damage it. You are just trying to get the gunk out of the way so water flow can flush the gunk out faster.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org

  • rystephan
    rystephan Member Posts: 19
    Thanks for the detailed help with diagram. Yes, the tight fit looks too close for comfort.

    If I find someone to come out, will they disassemble the LWCO like it says in the directions in order to clean it, or will they do the stick method you are describing?

    What can I do in the meantime from a safety standpoint while I'm waiting to hear back from service people? Should I just check often and make sure that the water in the gauge glass is not too low?

  • Jamie Hall
    Jamie Hall Member Posts: 19,960
    If they're any good they will have the necessary gaskets and disassemble the device to clean and check it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • 109A_5
    109A_5 Member Posts: 449
    Hello @rystephan,

    If the advice above is not enough or you want or need a more thorough cleaning. The Electrical switch assembly does come off (many screws and note where the wires go, shut off the power) which will allow a much more thorough cleaning and flushing out of the float chamber and cleaning of the float and its bellows, be gentle. It will require the old gasket scraped off and replaced with a new gasket, bought or made. I made one from silicone rubber sheeting so hopefully it is reusable. See this video below for a look inside.

    If you do poke up through the valve don't damage the float !!! The valve also comes off with the screws at the arrows. I would avoid this since those screws have a history of breaking. I would only take the valve off if it needs replacement. It also would require a gasket.

    https://www.supplyhouse.com/Mcdonnell-Miller-318900-67-12-Sylphon-Gasket-for-67-80
    https://www.supplyhouse.com/Mcdonnell-Miller-313300-37-39-Strainer-or-Blow-Off-Gasket-for-47536770

    McDonnell & Miller's Venerable #67 Low Water Cut Off For Steam Boilers
    https://youtu.be/HSZLaqm9TXE




    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • rystephan
    rystephan Member Posts: 19
    Thank you both, Jaime and 109A_5, for chiming in with such helpful info!!
    The diagram and video links were great. So grateful for this site and all the help available on it from experts like you. I feel like I'm going to know more than the guy who comes to service it! :D

    I just tried to flush it again and this time, water came out, but the burners did not turn off. Does that mean the float is stuck? I tried to blow it down one more time and same thing happened - burners did not turn off. I closed valve and within a few seconds, the burners turned off.
    The water was relatively clear but the sight glass water got dirtier as the level lowered.

    Until someone can service it, is there anything else I should do other than keeping an eye on the water level in the sight glass?
  • rystephan
    rystephan Member Posts: 19
    Thanks again in advance for all the help!
  • 109A_5
    109A_5 Member Posts: 449
    Hello @rystephan,
    The rust maybe binding or holding up the float. Crud collects in the bellows too restricting the movement of the float. More purging water through may help, but it sounds like it needs a good cleaning very soon. Other than shutting the system down for safety, assuming no system water leaks just monitor the water level very often. Get the M&M #67 serviced as soon as possible. I cleaned mine out just before this heating season, after over 50 years of service it needed a good cleaning.

    Not really a hard job, but a dirty wet job, took a few hours (I cleaned it good) including making a new silicone rubber gasket, I used a new paper gasket as the template. My M&M #67 may last another 50 years, the boiler and I probably won't. I may inspect it inside more often now since I shouldn't have to scrape the old gasket off each time.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,658
    MM recommends replacing the control if over 10 years old but many have cleaned them it's just time consuming and a dirty job.

    You really should get this fixed as you don't want to lose the boiler
    ethicalpaul
  • jhewings
    jhewings Member Posts: 126
    edited November 17
    Looks like you might have a pigtail on top of the LWCO? That might need cleaning too and certainly should be checked. Maybe take another picture further back?
  • ethicalpaul
    ethicalpaul Member Posts: 3,929
    Replace that relic, Until then, check your water level every day or two so you can do the job it is meant to do.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    Long Beach Ed
  • Long Beach Ed
    Long Beach Ed Member Posts: 796
    This stuff is history. It was so well made that McDonnell Miller ran an ad campaign thirty years ago touting "Hasn't it earned its retirement?" The things never died. But they need disassembly and cleaning. Nobody does that. The castings last forever, but the bronze parts inside do wear, and the switches become less dependable, which isn't good.

    In a perfect world you can disassemble and clean them. You can replace the switch every decade, and you can replace the bellows when they fail. Most of them just get hauled off for scrap after about 50 years, which is how long steam boilers generally last...
  • rystephan
    rystephan Member Posts: 19
    Thank you for your responses 109A_5 and EBEBRATT-Ed, and thanks All for the help!

    Definitely don't want to lose the boiler. I have a new service person coming Monday, but am not sure of their expertise with steam. The LWCO is more than 10 years old. we bought house 18 years ago.

    What should be the standard service for this?
    Will they disassemble and clean the M&M #67 ? or replace the float mechanism (series 6667 replacement mechanism) or put in new LWCO?

    Want to know the process so I know they are approaching it correctly.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,280
    edited November 17
    rystephan said:

    Thank you both, Jaime and 109A_5, for chiming in with such helpful info!!
    The diagram and video links were great. So grateful for this site and all the help available on it from experts like you. I feel like I'm going to know more than the guy who comes to service it! :D

    I just tried to flush it again and this time, water came out, but the burners did not turn off. Does that mean the float is stuck? I tried to blow it down one more time and same thing happened - burners did not turn off. I closed valve and within a few seconds, the burners turned off.
    The water was relatively clear but the sight glass water got dirtier as the level lowered.

    Until someone can service it, is there anything else I should do other than keeping an eye on the water level in the sight glass?

    This is of great concern. If the float IS stuck and the water level does drop below the safe minimum, then you will just need to purchase a replacement boiler. That may not be so easy with cast iron boiler shortages being what they are.

    Operate at your own risk. You might want to have this on hand when the service tech arrives. https://www.supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org

    rystephan
  • rystephan
    rystephan Member Posts: 19
    Oops, I didn't see the additional responses from early this morning when I responded Just now.
    Thanks for all your input! Jhewings - Ill attach another photo further back for pigtail.

    ethicalpaul - do you mean replace LWCO or boiler? Thanks, will continue to check water level.

    Long Beach Ed - thanks for info. Although it seems possible with all the great input and videos, I'm not in a "perfect world" right now to disassemble and clean myself. Sounds like a service guy is not going to spend the time cleaning it thoroughly either, and maybe not even replace the float mechanism at this point. My utica PEG boiler is 34 years old.
    Replacing the LWCO is maybe sounding like way to go...replace with same type?

    Just tried to flush again - water came out mostly clear but not super strong (better than yesterday) but the burners still did not turn off. Water level seems good, about 2/3 up the glass as marked.

    Thank you all for weighing in!


  • AdmiralYoda
    AdmiralYoda Member Posts: 496
    I was in this same boat a couple years back. I ordered the gaskets and removed the bottom drain section and switch assembly. The float comes out with it. I also removed the drain plug as well on the left side.

    I cleaned the float assembly in the kitchen sink and used various brushes and screwdrivers to scrape the gunk out of the LWCO body. Took some elbow grease but got it pretty clean.

    You'll have to make sure the old gasket material is off and the mating surfaces are super clean. Mine leaked on the first try. Had to go back and clean them again.

    Lastly, I now put a low dose of RectorSeal 8-way boiler additive in my boiler. Just enough to get the pH to about 10. Peerless says my pH should be between 7.5 and 11. Corrosion stops around 9 I believe. Now I have zero rust in my boiler and the LWCO is super clean. I still do blow-downs though just because.
  • rystephan
    rystephan Member Posts: 19
    Thanks EdTheHeaterMan, for the link! I was just looking at that same one right now.


  • rystephan
    rystephan Member Posts: 19

  • rystephan
    rystephan Member Posts: 19

  • JUGHNE
    JUGHNE Member Posts: 10,044
    I just helped (watched actually) my son clean his M&M 67 last week, in Chicago BTW.

    Less than 25 dollars in parts.

    Power off, drain boiler down at least below lower sight glass fitting, all the way is better.

    Remove and mark wires, remove screws....several pieces come off.

    Remove the "hot dog" float and carefully clean with nylon brush. Especially the accordion flex part.

    Remove the pigtail and clean it.

    Remove the sight glass handles and valve portion.

    Assure the openings are clear into the boiler. Use the protection rods on the sight glass to clean thru the valves into the boiler.

    Clean out the 67 body thru the float opening and insure the far end is open into the gauge tee fitting.

    Flush body and ports completely.

    We also changed out his sight glass with new rubber washers.

    Clean the flange surface of the float and body where the gasket goes.

    When replacing the float take note of the flex direction so it will move up and down.

    Apply Anti-seize to both sides of the new gasket.

    Reassemble parts, prime pigtail with water.

    Fill boiler and test blow down function of 67, the burner must shut off when blow down is done.

    shakingthrough
  • Long Beach Ed
    Long Beach Ed Member Posts: 796
    edited November 17
    Hold onto your wallet! Wait until you see the price of that Mcdonnell Miller Model 67 today! American iron doesn't come cheap anymore!

    Replacing it with a new, cheap electronic control would require unplugging a port in that boiler that has been happily plugged for two or three decades. It's not easily coming out, and I wouldn't want to be the guy messing with it.

    I would clean the control and replace its switch if needed. If you can find a knowledgeable man to do that it would be the cheapest and easiest way to go. Otherwise see what replacements the local service provider would be willing to install. Remember that this entire boiler has, in the words of Mcdonnell Miller, eh, earned its retirement.

  • rystephan
    rystephan Member Posts: 19

    Hello @EdTheHeaterMan

    Thank you for your following response:
    "This is of great concern. If the float IS stuck and the water level does drop below the safe minimum, then you will just need to purchase a replacement boiler. That may not be so easy with cast iron boiler shortages being what they are.
    Operate at your own risk. You might want to have this on hand when the service tech arrives. https://www.supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam"

    I greatly appreciate the help and have a few further questions.

    I am also very concerned about it, but am having difficulty finding someone with steam expertise on such short notice. How urgent is it? Is it safe to wait until after this holiday week?

    I can get the guys who have done my routine cleaning to come for "after hours" rates later today, but they have been inconsistent with the technicians they send over who supposedly "have steam boiler experience".

    I'm leaning towards scheduling them anyway, but If they do come, you mentioned in your response : "if the Float IS stuck"
    How will they assess it and know if it IS in fact stuck? Will they be able to do something simple first like the stick method up though the valve that you recommended earlier?

    Thanks again!

  • JUGHNE
    JUGHNE Member Posts: 10,044
    Even the float and switch is spendy but much less than the entire unit.

    The gasket is less than $10 and may be the only part needed.

    If the float is shot you can put it back together so it holds water and have heat.....

    This is TEMPORARY FIX ONLY !!!! you must visually monitor the water level as the boiler runs.
  • rystephan
    rystephan Member Posts: 19
    @JUGHNE, Thanks for the detailed cleaning procedure! Sounds entirely doable, especially with the videos online that also follow those exact step, but I don't want my first amateur attempt to be this week in Chicago with low temps 20 degrees or below! :D

    If I have service guys come after hours, would this be something they would do? (I know it would be at crazy rates unfortunately)

  • rystephan
    rystephan Member Posts: 19
    Guys, I need help!
    The service guy is here and he appears to be familiar with steam boilers, but is perplexed by what he is seeing.
    When he opened the ball valve on the LWCO, no water came out. He turned it off and tried again and same thing. He tried another time and some water came out (but was not gushing) and the burners turned off. That is the first time I have seen the burners turn off in several days while I was blowing it down
    He turned off power and continued to flush it. Initially, no water comes out and then if wait long enough, some comes out, but its weak. At times, when he does that, you can hear a clicking by the switch assembly which makes I'm think that the float is moving. (??)
    When no water is coming out, He says that it "is sucking air in". The sight glass has water in it above the float level.
    He tried to drain from back drain and when he opened it, same thing happened. No water came out at all, so that is strange. He is calling colleague now.

    Thanks for any insight.
  • jhewings
    jhewings Member Posts: 126
    Mine gunked up at the bottom of the #67 and very little water came out. I think I removed the pipe below and found the issue. Yours is more work to do this with those 2 elbows
  • rystephan
    rystephan Member Posts: 19
    So, he did a great job troubleshooting and talking through it, which I appreciated.

    As it turns out, the float mechanism appears to be working as long as the water level is low enough in the sight glass. He opened the valve and the water came out weakly, but once it got down very low, the burners turned off. He did that a few times and the burners consistently shut off. So, I'm glad the safety function appears to be working.

    He explained that once I fill it up with water so the sight glass is 2/3 full, the water comes out too slow and doesn't move the float enough to flip switch, so the burners stay on.

    As far as the slow water flow, there must be some clogged dirt and sediment that is impeding it, but they do not disassemble it or try to dislodge anything by pushing a stick up in the valve when opened. They are recommending a new one which seems appropriate given the age (at least 20 years old) and the way it is functioning.

    What doesn't make sense is why the water initially didn't come out at all, from both the LWCO and the drain at the back of boiler. After he played with the blow down valve several times while testing the float, the water came out of the back drain too. (brown water and not a strong flow)

    He had thought there was a "vacuum in the system" that caused the water not to come out. What would cause that?
    He thought it happened inadvertently when he turned the power off and it cooled down.
    However, no water came out when he initially blew it down while the heat had been on.

    Is there anything else that would cause the water to not come out at all?

    IMPORTANT update: I just opened the drain valve on the back of the boiler and no water came out at all. I turned it off and it is making a sucking sound. Opened blow down valve again on LWCO and no water came out of there either. Water was moving a lot up and down in the sight glass, almost looked like it was emptying and filling.
    What is going on?



  • Steamhead
    Steamhead Member Posts: 15,654
    The drain on the back of the boiler is probably as plugged as the one on the LWCO. Do as @EdTheHeaterMan says.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    rystephan
  • rystephan
    rystephan Member Posts: 19
    Thanks @Steamhead!

    @EdTheHeaterMan said to have a new LWCO available when the service guy arrived, but I couldn't get it in time because they came over this afternoon. Thats the plan though moving forward.

    Was there something else he said that I should be doing?

    After troubleshooting, the service guy recommended a new LWCO, but thought I could wait until after the holiday since the safety function on the cut off seemed to be intact (Float moved and switch turned the burners off) when the water level got low enough.
    As long as I monitor it, the urgency to install new one right away didn't seem to be there.

    Does that sound ok, or is there something else going on (now that no water is coming out) and is it more urgent?

  • jhewings
    jhewings Member Posts: 126
    Is this system 1-pipe?
    apexmech
  • pedmec
    pedmec Member Posts: 664
    You need to remove the top tricock stem from the valve. then take glass guard rod and push it thru the valve and into the boiler to see if the top tricock is plugged. removing the packing nut first will allow air into the tricock and break the vacuum. then the whole stem can be removed by rotating counterclockwise. check to see if it drains better. boiler should be off when attempting.

    The boiler is forming a vacuum because most likely your vents are not opening fast enough to let air in the system. you probably have bad main vents and some radiator vents that are not functioning properly. steam is condensing faster than its letting air in.
    Long Beach Ed
  • rystephan
    rystephan Member Posts: 19
    @jhewings: No, it's 2-pipe
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,280
    rystephan said:

    So, he did a great job troubleshooting and talking through it, which I appreciated.

    As it turns out, the float mechanism appears to be working as long as the water level is low enough in the sight glass. He opened the valve and the water came out weakly, but once it got down very low, the burners turned off. He did that a few times and the burners consistently shut off. So, I'm glad the safety function appears to be working.

    He explained that once I fill it up with water so the sight glass is 2/3 full, the water comes out too slow and doesn't move the float enough to flip switch, so the burners stay on.

    Since someone has proven that the low water switch is actually working then the urgency is gone. You have gone from DEFCON 4 down to DEFCON 2. Get the new #67 LWCO and you will be back to DEFCON 1.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org

    rystephan
  • JUGHNE
    JUGHNE Member Posts: 10,044
    My guess is that the lower water inlet to the 67 is nearly plugged.

    The lower sight glass port may also be nearly plugged.

    The water inlet port on the left is cleanable when the float is removed.

    All these openings into the boiler need to be open completely so you and the LWCO have the actual water level etc.
  • rystephan
    rystephan Member Posts: 19
    Thank you @EdTheHeaterMan!
    I'll sleep better knowing the urgency is gone.
  • 109A_5
    109A_5 Member Posts: 449
    Hello @rystephan,

    Wow, in my opinion the Service Tech did little for you for the price of a service call (he seemed lost by your description). That tech should have walked away with this issue repaired in my opinion, lame. You could have sat there for free and exercised it to minimally break up the rust and crud.

    For the money $$$.$$ for new 67 or an electronic LWCO and installation, It sound like it just needs a good cleaning. I would learn to clean it, it is just not that hard, just messy. The hardest part is scraping the old gasket off. If you don't, won't or can't get a OEM type gasket, gasket paper is available at most auto parts stores just make one.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    JUGHNE
  • 109A_5
    109A_5 Member Posts: 449
    Hello @rystephan,
    Just this easy. I cleaned the inside of the float chamber better than the guy in the video and flushed it out real well. Cover the gas valve so it don't get wet.

    Change the float on a Mcdonnell & Miller Low water cut off switch! (plus bypass trick)


    muddy low water cutoff


    There is more videos about the 67 this is the best I found so far.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • pedmec
    pedmec Member Posts: 664
    @EdTheHeaterMan you don't want to bang your head for another 4 pages. lol
    EdTheHeaterMan