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How To Properly Blow Down?

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I have been in my new house for a year now. It's the first home I have owned with steam and I love it but I have a lot to learn. I already ordered the Lost Art book.

My heating company is paid a subscription fee that includes a cleaning every year but I am concerned that they might not be doing everything they should be based on a recent service call where I had them come out to fix a non working radiator. They told me a bunch of inaccurate things and I ended up spending 4 hours and fixed it myself after the lies that they told me to get out of my house as quickly as possible.

On my boiler there is a McDonnell 47-2 feeder with LWCO. The service tech told me in the fall that I need to open the valve on the bottom of this part to drain the water once a week. He didn't tell me how to properly do this. When I try to do it with the boiler not firing it just makes a bunch of glug glug sounds with little discharge, but when the boiler is firing I was able to fill a 5 gallon bucket and the water still never came out clear.

After doing that I realized that I was probably introducing cold oxygenated water and it was not a good thing so I want to try and figure out the best way to do this before I do it again.

My pipes are often clanking also which doesn't bother me but I read that it could mean something is wrong? I also had a small pinhole leak on my wet return that I patched with a stainless repair sleeve but when it was leaking I was filling a 5 gallon bucket every 24 hours. I am hoping to at least keep things running properly before anything fails and expect to need to replace that return at some point but for now the leak is stopped.

I appreciate any advice you all can offer. Photo of the boiler attached. Thank you!



Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    That low water cutoff has a ball valve (big yellow handle) on the bottom. That is your blowdown, and you need to open it once a week or so -- wide open. At first the water may be gunky, but it should at least not be gunky after a few pulls on the valve. It won't be clear -- just not gunky. Usually a gallon or two will do it. There are various ways to play it -- but I usually open it wide and watch the water level in the sight glass, which should drop quickly. Close it. Rinse and repeat a few times until the water is at least so so. If you do this with the boiler running, the boiler should shut off when the water level in the sight glass drops too low.

    Then bring the water level up to where it belongs and let the boiler run. You won't introduce enough new water to do any harm.

    Plan on replacing that whole wet return. Where there is one pinhole, there will be many.

    The clanks could have many causes. If they are really water hammer, it's worth checking all the piping to make sure it is pitched properly.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • LegendsCreek
    LegendsCreek Member Posts: 65
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    Thank you very much Jamie. My biggest concern was adding too much cold water while the boiler was running and doing damage to it. Another strange thing is the PSI gauge. This morning it was at 5 but not firing, then it fired for 30 seconds, then shut off and the gauge went up to 8. The other day it was running full blast and the gauge was at 0. Is this normal behavior?
  • pecmsg
    pecmsg Member Posts: 4,861
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    Thank you very much Jamie. My biggest concern was adding too much cold water while the boiler was running and doing damage to it. Another strange thing is the PSI gauge. This morning it was at 5 but not firing, then it fired for 30 seconds, then shut off and the gauge went up to 8. The other day it was running full blast and the gauge was at 0. Is this normal behavior?

    If you're talking 5#'s of pressure that's too high. With that gauge you really shouldn't see it move much. To accurately read the pressure you need a 0 - 3 # gauge. Keep the 0-30 connected, its required by code.

    Search the site for How To add a second gauge.

    Doesn't sound like your service provider has given any service, time to find another provider. Where are you located?
  • LegendsCreek
    LegendsCreek Member Posts: 65
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    I had a feeling that something might be off with it. I just looked this morning and the gauge is at 0. I am attaching 2 photos from yesterday. The first photo shows the boiler at 6, then it fired for 30 seconds and turned off which jumped the gauge to 8. This is abnormal? What should I say to my service company when I call?

    I am in Londonderry, VT. They performed my annual boiler service last August but I have no idea what they did or didn't do.




  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    edited March 2022
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    The two essential benefits of the lwco blowdown are:
    1. verifying that the boiler burner cuts out, in this simulated low water condition,
    2. flushing out debris from the float chamber which might prevent it from working.
    I hope the service company also checked the chimney flu, as there is some discoloration/scorching around the burner plate.
    In addition, the service should include the cleaning of the pigtail under the gauge/pressure trol, so that it can properly sense the pressure, and cleaning the gauge glass, so the water level can easily be seen.—NBC 
    ethicalpaulLegendsCreek
  • LegendsCreek
    LegendsCreek Member Posts: 65
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    Thank you very much for that information. How much water should I expect to come out during a lwco blowdown? I haven't done it enough while firing to have it turn off but I will try it to make sure it cuts off. Someone drew a black line on the sight glass which I am assuming is the water level for where the LWCO should engage but I am not sure.

    You mention scorching around the boiler plate. Where in the photo is the boiler plate? Thanks very much!
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    Shouldn't take more than a gallon or two, if that, done in two or three quick shots. One of them long enough to trip the LWCO. Don't dribble it out. Take the valve full open, then full close, then full open, etc.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    LegendsCreek
  • LegendsCreek
    LegendsCreek Member Posts: 65
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    I tried this morning to test the lwco. I got to about 3 gallons but the water level in the sight glass kept looking like it was bouncing (I am assuming water was filling as fast as I was trying to drain it). I never got to lower the water level enough to trigger a lwco.
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    This is a serious thing to consider as in dangerous.

    I think you need the sight glass valves cleaned going all the way into the boiler.
    Also the LWCO water connections.

    The water is not added that quickly to overcome the usual drop in the sight glass from blow down. The water fill line should be connected to the boiler return line and fills at that point, quite a ways from the glass location.

    You may have to open the LWCO for cleaning, possiby replacement.

    While all this goes on, you should assure the control pigtail is clean and add a 0-3 PSI gauge. It is obvious that what you have is faulty. Just leave it connected and add the new one above the pigtail. Install copper pigtail if you have an iron one now.

    You need a new service company. May one for the steam system/boiler and perhaps another just for the oil burner?

    It is imperative that the burner shut down when you blow down the LWCO.

  • neilc
    neilc Member Posts: 2,703
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    to check that shut down on the LWCO, shut off the make up feed, you should have a manual valve or 2 there somewhere, along with a fast fill bypass perhaps,
    don't forget to reopen the manual valve(s)
    known to beat dead horses