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low water cut off - replace or clean?

1 pipe steam, lwco looks like the attached pic (sorry, did not take picture of actual).

It never really flushed well when I pushed down the yellow handle -- it kind of always trickled out slowly.

And recently the float or other parts of it are all gluncked up, so that the auto feed sometimes adds 5 or 6 gallons too much before it registers as a proper water level (and, at that point, the water is a foot higher than the glass gauge, so then I'd need to drain it back down and start again). I can fix that temporarily by draining and such, so it works OK now and seems to be at the right level. But my service company says the lwco's shot, and wants to replace the whole lwco (for over $800!).

Is it possible just to take the thing apart and clean out the crud and get it working again? Or am I better off scrapping it and getting a new one?

Thanks in advance


Comments

  • Changing out the old one for an identical new one is pretty simple. then you will have time to clean the old one, to use for the next replacement. make sure to ream out the connecting piping.
    It will probably have to soak in water for a day or two to get all the rust out, with the switch removed, and at this time of the year, you may not want to be without heat.--NBC
  • vaporvac
    vaporvac Member Posts: 1,520
    Have you considered a probe LWCO so you could dispense with the testing every week? Can't comment on the price, but it's not a difficult change out either way and the actual LWCO isn't that expensive.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • JUGHNE
    JUGHNE Member Posts: 8,949
    How old is your LWCO?
  • Chris_L
    Chris_L Member Posts: 218
    The pros probably won't recommend this, but this homeowner has cleaned a couple of them out while they were on the boiler. After turning off and draining enough water out of the boiler, you can remove the four screws on the bottom that hold the LWCO valve, and then gently scrape the rust and gunk off the inside walls of the float chamber. Gently spray water up into it to rinse, and move the float to see if is free. (It is spring loaded and will go down when there is no water to float it.) You'll need to buy or make a new gasket to reinstall the valve.

    Weather you buy a new one or clean your existing one, I'd recommend using Steamaster tablets to treat your boiler water.
    I followed the recommendations of some on this site to use them, and since then have never had any problem with the LWCO gunking up. In the past, I could count on no water coming out after opening the valve at the end of the summer when the boilers had been off for a few months (because the gunk had sealed over the valve opening) . This fall, after first using the tablets last winter, the water gushed out. And every time I've blown down the boilers since them, the water has flowed freely and float had moved as it should.
  • Fred
    Fred Member Posts: 8,518
    McDonnell Miller recommends replacement after 10 years and annual cleaning. There is nothing inside the unit but a float attached to a hinged switch and the ball valve for blowdown. Order a set of gaskets, one for the blowdown valve and a round one for where the switch mounts on the end of the unit. The unit is cast iron. I would wait for warm weather to take it off, take it apart and scrape out the rust/gunk. You have to do it from both the valve end and the switch end. A really simple job that takes maybe a couple hours, including taking it off of the side of the Gauge glass and re-installing it. They are very well built and there really is nothing to wear out, except maybe the switch, which never happened to me in a unit I have that is 30 years old.
  • JUGHNE
    JUGHNE Member Posts: 8,949
    The only thing I can think of is with all the gunk cleaned out would be if the float were partially filled with water. (Don't know of this happing, but seems possible).
    The float would go down shutting off fire and opening fill valve but if the float were heavy with water it would be slow to rise and overfill boiler. Just a thought. Also if bellows on float arm fails it would be obvious. Is there a strainer on the water inlet to this?
    Of course the main thing is to shut off fire if float drops.
  • Fred
    Fred Member Posts: 8,518
    There is no strainer on this unit and no bellows on float arm, just the copper/brass float itself that is on a hinge that has contacts on it to make (when float is up or break when float is lowered by lack of water). I doubt if it would leak but anything is possible. They sell replacement floats if needed.
    If the OP wants to replace the entire unit, there are several new ones on ebay at a fraction of the cost from a supply house.
  • JUGHNE
    JUGHNE Member Posts: 8,949
    I've never had one of these apart but it seems there must be some seal between the mechanical arm movement in the water and the electric switch outside the float cavity.
  • Fred
    Fred Member Posts: 8,518
    There is. there's a metal plate and a gasket, maybe two. It's been a while since I had mine apart but it is a really simple assembly.
  • Thanks everyone, this is all great info. If it were spring or summer I'd take it apart and have some fun playing with the cut-off. But it's too cold to have fun tinkering for hours until I figure it out. So I will have it replaced. Funny, though, I find a price of $217 or $230 at these websites (can't tell the differnece -- minivolt?) supplyhouse.com/Mcdonnell-Miller-149600-67-G-67-Float-Type-Low-Water-Cut-off-for-millivolt-service-Steam?gclid=CKHO8ODR9MMCFWYV7Aod7RIAYA
    or
    supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam?gclid=CM22n-LR9MMCFXBp7Aod2WkA2g
    But when I look on eBay I see them for over $325. Someone said eBay is cheaper, but I don't see it(?) Did I compare an apple to an orange?
  • vaporvac
    vaporvac Member Posts: 1,520
    Is there a situation where a float type is better than a probe?
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Ebay is not always cheaper, and when it is "Caveat Emptor".--NBC
  • JUGHNE
    JUGHNE Member Posts: 8,949
    This is 2 for one; LWCO and auto feeder. If he were probe than would need to add feeder or just shutdown of heat. Manual blow down gets the homeowner more aware of his boiler operations as we have noticed here.
  • BobC
    BobC Member Posts: 5,229
    Don't by one from EBAY unless they state it is working, read the description carefully. If it does not work EBAY will force the seller to give you back your money but you will be out the time it took to find this out.

    I'd just replace it with a probe type LWCO if it were on my boiler.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • j a_2
    j a_2 Member Posts: 1,796
    discussing pricing and commenting on price is not allowed on this site…..To the h/o who says its easy, maybe it is and maybe it isn’t….Maybe the installer put a pipe in its way or the wiring is suspect….Maybe and just maybe the pro saw something you didn’t….120s and 24s are the same it only take a small rewiring of the sw. in the unit…..I did not see a pic
  • Chris_L
    Chris_L Member Posts: 218
    On the question of a probe vs. a float type LWCO, is it even possible to use a probe type on a gas millivolt system? Assuming there is no power to the boiler, and you don't want to add it, thus keeping the boiler off the grid.

    (I assume this doesn't apply to the OP since he has an automatic water feeder, but for those of us with millivolt systems and manual feeds, I thought the float type LWCO was the only option.)
  • As the probe type needs external voltage to work, I think the float type would be best for a straightforward replacement.
    If you have the replacement in your hand, it makes it easier to see what difficulties are present. Also the probe will need a tapping into the block, plus plug removal--NBC
  • Fred
    Fred Member Posts: 8,518
    edited February 2015
    j a said:

    discussing pricing and commenting on price is not allowed on this site…..To the h/o who says its easy, maybe it is and maybe it isn’t….Maybe the installer put a pipe in its way or the wiring is suspect….Maybe and just maybe the pro saw something you didn’t….120s and 24s are the same it only take a small rewiring of the sw. in the unit…..I did not see a pic

    I'm the HO who said the rebuild/replacement was a fairly simple task. I did however say I'd wait for warm weather. One never knows what surprises one might face.
    I would stick with the Float type McDonnell Miller #67. They are typically mounted off of the bottom of pipe of the sight glass and finding a tapping on the boiler and getting the plug out is too much of a challenge on an older boiler.
    As far as buying one on ebay, I bought one for half of the cost that the poster got from Supplyhouse and brand new, in the box. The items on ebay are very dynamic so you do have to watch and I would never buy a used one. The OP already has a used one.
    EDIT: BTW, there is a New, in box McDonnell Miller #67 on ebay right now for about 75% of the cost the OP got from SupplyHouse. I'm just sayin...
  • BobC
    BobC Member Posts: 5,229
    Your right about the probe type needing power (not good if power goes out on a millivolt system) and the problems you might encounter getting an old plug out of the boiler.

    That leads me to retract my statement about replacing it with a probe type LWCO.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • vaporvac
    vaporvac Member Posts: 1,520
    I think the original poster doesn't have a millivolt system, but he'd still have a problem with the plug, perhaps. I'm certainly glad I kept my HWheater off grid cuz 1 day after install, no electricity for the day!
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • BobC
    BobC Member Posts: 5,229
    I agree that a standard gas HW tank is a wonderful thing if you have modest HW needs. It's not expensive to install or run (6 or 7 therms a month in summer) and they don't need electricity.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • JamesC in Stamford CT
    JamesC in Stamford CT Member Posts: 92
    edited February 2015


    Wow, what a lot of interesting chatter I generated with my original question. It has helped me quite a lot, thanks averyone. I now attach photos of my lwco and setup. I have an auto feed -- so my question is do I get the automatic reset or the manual reset. I found some interesting conversations int he archives of this board for prople without an auto feed. Which one is recommended for my setup?
    Auto reset: http://www.supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam
    Manual reset:
    http://www.supplyhouse.com/Mcdonnell-Miller-149700-67-M-67-Float-Type-Low-Water-Cut-off-w-Manual-ResetSteam
  • Fred
    Fred Member Posts: 8,518
    You want the auto reset unless you want to go down and reset it anytime it trips on low water. I'm sure what you have now is auto-Reset.
  • rpapagolos
    rpapagolos Member Posts: 2
    James, this is the same LWCO I had on my old boiler. If you are handy you can buy the new one and replace it. I did mine twice in the last 25 years. If you take the old one apart you may find the float rusted and gunk up maybe with a hole in it, you can buy a new float SKU: 344200 and gaskets and rebuild the old one this summer it's not that difficult and a spare is handy to have. Both times my LWCO failed it was on the coldest! day in RI. you can buy the parts on the same web site you posted. http://www.supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam
    I would suggest replacing the plug in the bottom of the unit as part of the rebuild. Follow the Mfg. instructions about blowing the LWCO down I did mine once a week takes 5 minutes.
  • tim smith
    tim smith Member Posts: 2,398
    We tear those,#47s, 63s and 150s down all the time for internal inspections by city here. Takes about an hr to pull apart, clean, inspect and put new gaskets in and assemble. They are not too complicated. You have to be methodical and alert to any issues with disassembly and assembly but not hard. Might not hurt to have new float on hand. When apart, flush all tubes, scrape out inside of cast body. Rinse, check float for any water in it and clean. Assemble and test, test test. Make sure it shuts off boiler in low water condition and also feeds water properly. Btw, turn off 1st and drain water down below low water cutoff level. Or just replace?