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Where's the water going?

if your gauge shows 4 psi, you should lower the pressure by way of your pressuretrol to below 1 pound.if your pressuretrol is unable to handle that low a pressure then i strongly suggest a vaporstat and low pressure gauge[0-3 psi] which you can install yourself.
your system from your description appears to be a combined parallel and counter flow arrangement, and would benefit from lower pressure.mine does most of its heating in the 6-10 ounce mark.
still water at room temp occupies a standard volume; however when boiling that same volume can increase due to the presence of steam bubbles.when the boiling stops, the collapse of the bubbles cause the level to be suddenly lower.it's difficult for a sight glass to show a really accurate level in your boiler while steaming.ancient boilers had a surge column to make the sight glass more accurate.
you may see the waterline behave itself after you have lowered the pressure.if not then the next step would be skimming the boiler clean--all described in "the lost art of steam heating" available here.--nbc


  • cmannering
    cmannering Member Posts: 2
    Where's the water going?

    I had a Burnham Megasteam boiler installed, and am troubled by two things. 1. When the boiler is cold, the water level is exactly where it should be, as documented in the manual. During a heat cycle, the water level in the sight glass quickly goes all the way to the bottom, and out of sight below the lower brass fitting. The label on the side of the boiler, marked "Lowest Permissable Water Level", is only about a half inch below the lowermost sight glass fitting and the low water cutoff (McDonnell probe type) doesn't seem to cut the burner off when the water drops that low. I should note that the low water cutoff device taps into the boiler at a height that's between the upper and lower sight glass tappings. Why isn't it cutting the burner firing when the water goes below the level at which it's tapped into the boiler? 2. During the time when there's no visible water in the sight glass and the radiators are hot, the pressure guage will rise to about 4 psi, and then the burner will cut off, the water level will begin to return, and as it gets to be about an inch from the bottom of the glass, the low water cutoff will kick in (as evidenced by the red flashing light) and then return to "normal" low water cutoff status as the water level rises. During this rise in return water, the pressure will also be dropping, and then the boiler will fire again until the thermostat is satisfied. I've tried adding a little water (all the way up the sight glass)to compensate, but even when filling the water above the proper level, all of the water disappears from the sight glass. When the thermostat is satisfied, and the burner stops firing, the water level returns to the boiler completely within 3 or 4 minutes, so if the water is coming back that fast when the boiler shuts off, why doesn't it come back fast enough to maintain the 1/2 mark on the sight glass while the boiler is firing? I'm worried about my boiler cracking because it's firing with no visible water in the sight glass. There is some of that brown crud in the water, and I plan to flush the boiler, but I can't see this being the cause of my troubles. This is a 1 pipe residential system, with a wet return at the far end of the main, and half of the radiators drain back into the main and towards the boiler, not the wet return. 5 radiators total. All have new, working vents, and I replaced the main vent, and hear the air leaving all of them at the beginning of each cycle. Any advice?
  • cmannering
    cmannering Member Posts: 2
    Where's the water going?

    Thanks for that, Nicholas. I'll adjust the pressuretrol device, but there are two adjustments.. the main and the differential. Both are set to about 2. If I drop the main to 1, how will this affect the setting of 2 on the differential?
  • klaus
    klaus Member Posts: 183
    Burnham Megasteam Water Level and LWCO Advice

    Following up on this subject, regarding the low water cutoff... (Burnham Megasteam/Beckett AFG burner, probe style McDonnell LWCO)... The water at cold start is nearly at the top of the site glass, but after making steam and the water level drops to below the bottom most part of the site glass (the level seems to bottom out inside the lower brass fitting or the site glass, which is the level of the label marking the lowest safe level to operate the boiler at)the burner will stop firing, and as the water level starts to rise, the red light on the LWCO will flash for about 10-15 seconds, and eventually go out, during which time the burner will start again, water level drops, pressure guage reaches just under 2LBs, burner cuts out, etc. The burner cut out/ re-ignition will occur maybe 4 or 5 times towards the end of the cycle/thermostat satisfaction. The red light on the LWCO doesn't usually come on, but my question is this: Why doesn't the LWCO do it's thing when the water level drops below the level at which the probe enters the boiler? The point at which it enters the boiler is at a height that's about midway on the site glass, so why does the LWCO let the burner keep firing until I can see the water level disappear from the site glass altogether? Shouldn't the LWCO red light go on the instant the water drops below the probe level, and cut the burner from firing? I only see that LWCO red light come on long after the burner stops firing, and as the water is coming back from the radiators to the boiler. The boiler will be at the full water level in less than 5 minutes from the cycle's ending/thermostat's being satisfied. One thing I noticed is that if I begin closing (not all the way) the upper valve of the site glass as the burner is firing/making steam, the water rises quickly towards the middle of the glass. Is this the true level of the water, or is this surge while closing the valve caused by a vacuum when I mess with the valve? I started messing with the valves to make sure they weren't clogged up, and causing delayed/inaccurate readings. Either way, I'm worried that the water is going too low during the cycles, and the LWCO's not doing it's job.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    ask professor google

    get the numbers off the pressuretrol, and search for the manual, and therefore lower the pressure as low as possible. both settings need changing.--nbc
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Drop the differential

    to 1, then drop the Main to halfway between 1 and 2. This will stop the burner at 1.5 pounds and restart it at 1/2 pound.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

  • Hi Chris-
    As already mentioned your pressure is too high. Follow Steamhead's advice. He's very much a "steam pro".

    Also if you don't have them already may I suggest that you get Dan's books on steam heating? (See "A Steamy Deal" at the bottom of this page) They are books every homeowner who has a steam system must have. Easy reading, crammed full of facts and diagrams so that in an evening or two you'll know all about steam heating systems.
  • Jim Franklin
    Jim Franklin Member Posts: 170

    I just had a new boiler doing the same thing.

    Shut off the system and drain all the water from the boiler, fill the system, heat up and repeat the draining.

    You may just have a dirty boiler and this may be an easy fix.

    There could be other problems but keep it simple first.
  • jim walsh_2
    jim walsh_2 Member Posts: 12
    disappearing water

    The answers you have received so far regarding the pressure settings on your pressure control are correct. However, it sounds to me like your boiler is surging. This is caused by that "brown crud" at the top of the sight glass. That crud is also floating on top of the water in the boiler. When the boiler is trying to make steam, all that junk prevents the steam from leaving the boiler. The boiler MUST be skimmed to remove the crud. Draining and refilling will not accomplish this. That crud has to come off the top.
  • Chris M_2
    Chris M_2 Member Posts: 67
    Where's the Water Going?

    I already have the main on the pressuretrol set to between 1 and 2. The differential is set to 1. (There are two things to adjust, main and differential). I've also already skimmed the water. I did this by removing a plug in the back of the boiler, and slowly feeding in water to let the surface water trickle out. I did this for about an hour, and not much brown stuff came out. I could however see transparent oily material in the water I removed. I don't think dirty water's the culprit here. I'm also still wondering why the LWCO isn't interrupting the burner when the water level falls below the point at which the probe enters the boiler, but seems to light red only when the burner stops firing/fan still moving, and the water is on it's way back from the radiators to the boiler. Can anyone speak to this issue specifically? For those who asked for pictures of the piping, I'm working on it, and thanks to all for your responses.
  • steve_29
    steve_29 Member Posts: 185

    James I skimmed this boiler of at least 30 gallons with no success, until I drained the entire system 3 times.

    Worked like a charm now.

    While I agree one would guess that just skimming would do the job, it didn't.
  • Chris M
    Chris M Member Posts: 7
    I skimmed and drained, problem solved

    I let my Megasteam boiler cool down this past Saturday (kept my pellet stove running) and skimmed it again. I skimmed 2 1/2 joint compound buckets worth. Instead of using the harder to reach 1 1/4 inch tapping at the rear of the boiler, I closed the lower site glass valve, removed the glass, and then used the upper site glass valve as my skim port. After I skimmed the estimated 14.5 gallons worth, which took about 2.5 hours to do, I replaced the glass. I then drained the boiler altogether, and filled it up to the operating level again. Although the water still has traces of rust particles in it, the water no longer surges below the low water cutoff, and better yet, the waterhammer has completely disappeared, which was so loud that it used to wake us all up in the morning. I thank all of those who gave me advice, and I have to say that this whole steam heating thing is the coolest stuff in the world, and have a lot of respect for the people out there who know what they're doing and take pride in their work. The guy that installed mine didn't skim my boiler after he installed it, but he surely must have known that this is something he should have done, being a "master" and all. This is the kind of stuff that causes people to lose confidence and trust in people, but the payoff is that I as a homeowner now know more about my home heating system than most homeowners do, and have the good people on this list to thank for their help in getting me there. Thanks again...
  • Jim Franklin
    Jim Franklin Member Posts: 170

    I'm happy all is now well.
This discussion has been closed.