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Water level drops and LWCO trips every cycle

whitwo
whitwo Member Posts: 50
I recently had 2 sagging main lines fixed and ever since I've been experiencing something odd. During the cycle the water level slowly drops until the LWCO trips. The water level doesn't bounce and the water isn't cloudy/dirty. I'll usually get 10-15 minutes of run time before the LWCO trips. Any idea what might be causing this?

Things I've done:

Cleaned the main vents
Cleaned some noisy radiator vents

My next move is to skim just in case the water is dirty but I just can't tell by looking at it. Before the mains we're fixed the water would get dirty and the water level would bounce like crazy. My assumption is this was from water collecting in the mains and eventually making its way back to the boiler (after some loud hammering along the way). It also produced some wet steam that gunkes up the vents (hence the cleaning). Maybe some of that is sticking around in the water?

Other than this issue, the system seems is running great. Quietest it's ever been since we moved in. Heats super fast.

Only other thing to note, and I may be imagining it, but when I drain water from the boiler it doesn't move in the sight glass for a few seconds even though the water is coming out, then it drops all of the sudden.

Any ideas? Much appreciated.

Comments

  • jhrost
    jhrost Member Posts: 57
    Just to clarify, you say when you drain water from the boiler. Is this necessary because after the low water cutoff is activated water later makes its way back to the boiler and causes a high water condition? Could be you still don't have the proper slope in your return, or maybe the lowest point of your wet return near the boiler is somewhat clogged?
  • acwagner
    acwagner Member Posts: 505
    Try skimming first and see if that helps. With the new work on your mains, oils and such were introduced into the system that will need to be removed.

    Skimming is different than draining.
    Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
    18 Ounce per Square Inch Gauge
    Time Delay Relay in Series with Thermostat
    Operating Pressure 0.3-0.5 Ounce per Square Inch

    Hap_Hazzard
  • whitwo
    whitwo Member Posts: 50
    Correct. The water level comes back relatively quickly.

    I wondered about the wet return. Is there a good way to test for that or is the best thing to clean it out?

    > @jhrost said:
    > Just to clarify, you say when you drain water from the boiler. Is this necessary because after the low water cutoff is activated water later makes its way back to the boiler and causes a high water condition? Could be you still don't have the proper slope in your return, or maybe the lowest point of your wet return near the boiler is somewhat clogged?
  • whitwo
    whitwo Member Posts: 50
    Just to clarify, no new pipes were added, just some broken hangers replaced.

    > @acwagner said:
    > Try skimming first and see if that helps. With the new work on your mains, oils and such were introduced into the system that will need to be removed.
    >
    > Skimming is different than draining.
  • acwagner
    acwagner Member Posts: 505
    edited December 2019
    Got it.

    When the LWCO trips does it add more water, or does the waterline return quick enough that no water is added?
    Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
    18 Ounce per Square Inch Gauge
    Time Delay Relay in Series with Thermostat
    Operating Pressure 0.3-0.5 Ounce per Square Inch

  • What is your pressure? The water in the wet returns will rise up 1.75 inches for every OUNCE of pressure, and that can drop the waterline in the boiler. My one-pipe system operates at just a few ounces, except when coming up from a setback, and then it rises to 10 ounces, so excessive pressure is not needed or desirable.
    Improper boiler supply piping coupled with oily, or chemically “enhanced” water can also throw enough water up into the system to lower the boiler waterline.
    Adding a 0-3 psi gauge graduated in ounces will help to verify the correct operation of the pressuretrol, and it will show the capacity of the main vents.—NBC
  • jhrost
    jhrost Member Posts: 57
    You say the water in the sight glass doesn't bounce much, does the top of the glass show water droplets running down? I think the skimming advice is good. I do mine a few times a year, and at the same time take off and clean the sight glass. It always seems to help and I get a clear idea of what is happening with the water level.

    Along with the LAOSH admonition to crank down the pressure this skimming is probably one of those important things you can do yourself , even though the guys who installed your boiler didn't bother with it and or said it didn't matter (they may have been thinking that they had screwed up your near boiler piping so bad etc that nothing else would probably help anyway).

    If cleaning and skimming doesn't solve (and your system otherwise functions reasonably) the problem of the unnecessary water being added and having to be drained our later, you might also want to consider getting a water feeder with a longer time delay like the Hydrolevel VXT I think. I just close the valve on my waterfeeder since it really isn't an absolutely required item and can just result in your system getting flooded sometimes.

    You might also want to check the two wheel valve things at the bottom and top of your sight glass to make sure they are fully open , in case that is causing the effect you mention in the last paragraph of your first post. When I skim and clean the sight glass I usually open the bottom valve and drain some water from there until it runs clear - there always seems to be some muddy stuff coming out initially and I always figure that if this is totally clear the sight glass may stay clear longer.
    RedChops
  • coelcanth
    coelcanth Member Posts: 89
    edited December 2019
    the original poster mentioned the waterline did not really surge or bounce but rather dropped gradually lower during the cycle.

    is that how a boiler in need of skimming or cleaning behaves ?
    i've always pictured a more wildly moving waterline when someone describes surging.. but i ask because i have little real world experience
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,756
    Foaming can drive a lot of water out without making the water line bounce. Take a cup of water out of your boiler and boil it on the stove and see if you see any foaming.

    Another possibility would be scale buildup in the gauge glass fittings. If one or both are closed down to 1/8" or less, it would damp out the water line fluctuations. For that matter, so would partially closing one or both of the gaugecocks. Make sure they're all the way open.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • whitwo
    whitwo Member Posts: 50
    Thanks for all the input. I'll try and answer all the questions:

    "When the LWCO trips does it add more water, or does the waterline return quick enough that no water is added?" Yes, it adds more water. I turned down the amount of water that gets added by the auto feeder. I have to drain 2-4" a day.

    "What is your pressure?" Really good question. I have one of the less useful 0-30psi gauges and need to replace it. I've got my cutout set pretty much as low as it will go. I've been considering replacing with a vaporstat instead of the current Honeywell PA404. The way that the water line drops seems like it could be because of pressure. Slow and steady, like pressure is building.

    "You say the water in the sight glass doesn't bounce much, does the top of the glass show water droplets running down?" Yes, I do see water droplets. Not as much as before the main lines were fixed. The water line really doesn't bounce at all. It used to surge several inches. I would call it a small jiggle now, as the water line steadily drops.

    "You might also want to check the two wheel valve things at the bottom and top of your sight glass to make sure they are fully open" I will clean the sight glass and run some water through the bottom to be sure it is clean.

    "Foaming can drive a lot of water out without making the water line bounce. Take a cup of water out of your boiler and boil it on the stove and see if you see any foaming." Will do. I'll report back what happens. What do you mean by "damp out the water line fluctuations"?

    Thanks again!
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,756
    whitwo said:

    What do you mean by "damp out the water line fluctuations"?

    If the passages in and out of the gauge are narrowed down by scale buildup or partially closed gaugecocks, water won't be able to move in and out of the gauge quickly enough to show that the boiler is surging or kettling. While it will reflect the water level over time, it wouldn't be able to respond quickly enough to indicate rough boiling.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • JUGHNE
    JUGHNE Member Posts: 9,757
    Your lower sight glass fitting going into the boiler may be partially plugged. You can drain down the boiler, remove the packing nut and usually unscrew the stem out. A small bottle brush will pass thru into the boiler to assure it is open.
  • nde
    nde Member Posts: 48
    Check the pitch of the mains, they could be close to level post new hangers vs sloping toward the return which is what they should do. In this case condensate is draining back slower which cause LWCO to kick in.
  • Jamie Hall
    Jamie Hall Member Posts: 18,923
    The combination of your various complaints leads me to the first place I would go. You have a slow overall drop in water level (it may or may not be bouncing, but overall, slow). You have no good way of knowing what the pressure really is doing (you can add a 0 to 3 or 0 to 5 gauge, but don't replace the 0 to 30 -- the insurance folks want it there), but it is likely increasing slowly.

    The water does come back when the burner shuts down.

    Wander out into the rest of the basement and look everywhere for a pipe or pipes which are within a couple of feet above the water line of the boiler. If you find some, figure out whether they were originally meant to be dry returns or, far more likely, wet returns. I'd be reasonably certain if you find some that that is where your water is going; in any event, they shouldn't be there. If they were originally meant as dry returns (or even extensions of the steam main) repipe and rehang them to make them so. Likewise, if they were originally meant to be wet returns, repipe them and drop them down so that they are wet all the time.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • whitwo
    whitwo Member Posts: 50
    Quick update - decided to clean the sight glass. Bottom valve was pretty dirty and skimmed a little from that port. Water was barely coming out the top. Turns out there was a chunk of dried pipe sealant stuck in the valve. I cleaned it, skimmed a little and the water level seems to be acting normal now.

    Thanks for all the help. I plan on doing a longer skim tomorrow from the skim port.