LWCO tripped AFTER burner shuts off?

ChrisJ

WM EG-45 on single pipe system with 372 sqft of radiation. Thermostat is VP8000 series.  No water feeder, manual feed only.



A few times now I've been awake to watch my system during a 3 degree recovery in the morning (66F to 69F).  Pressure stays very low and system runs nicely, sadly the clicking and klacking of the Hoffman 1As is what wakes me up rather than the heat.



Water level ends up pretty low in the gauge glass, maybe 1/2" high visible at times which is still considered safe in this boiler.  As soon as the burners shut off due to the thermostat being satisfied I appear to get a pretty decent vacuum in the system and the water level drops low enough the gauge glass empties and the LWCO trips (probe type).  It takes a good 5 minutes for the water to return enough to satisfy the LWCO.  Water level returns to normal after 10 minutes give or take.





I'm assuming this doesn't seem to matter as the LWCO is not tripped until AFTER the burners shut off, but my concern is, is this normal?  Should I care?  Does this suggest that on a colder morning I may run low on water and trip the LWCO? 



My wet return is all copper and less than a year old.  I have two dry returns which are pitched well.  I am not sure what I can do to get the water back to the boiler faster? 



Picture is from a few mornings ago and a few minutes before the burners shut off.





 Thank you for your time.

Chris J

BobC

Water hiding

Chris,



It doesn't look like you have an automatic water feeder which is good because you don't want to feed water into a boiler that might not run for many hours because of the dissolved oxygen in the fresh water.



The water level  dips as the burner runs and that water finds it's way back to the boiler after it cools, about how long does it take that water to find it's way back? The question is where is that water hiding? You said the wet returns are new copper, are your dry returns clean so the condensate easily finds it's way back to the boiler? Make sure there aren't ant low spots in the piping.



Did you have this problem before the work was done? Are your main vents working ok? If it stays like this your probably ok but if it starts to get any worse you will have to find out whats going on.



Bob

ChrisJ

how long

Bobc : it takes around 10 minutes for the water level to return to normal after shutting down.  There is a slight sag in one dry return but its very slight so I haven't bothered to mess with it.  Both dry returns are clean.



Main vents are working great and I have no idea if the problem existed before I installed the new system.  Previous system was undersized by at least 50% with two clogged main vents and a clogged iron wet return.





Why does the water level drop a good inch immediately after the burners shut off?

nicholas bonham-carter

vacuum

when you shut it down, try and loosen the main vent and see if that breaks the vacuum [are the vents hoffman 76?]--nbc

ChrisJ

main vents

Main vents are three Gorton 1s on a 29' 2" main and a single Hoffman 4A on a 11' 2" main.  I did this to get the system balanced due to the short main hogging all of the steam on startup.  Worked out rather well so far.



I could loosen the cap on my skimmer and crack the valve, but what effect should I see when I break the vacuum?

crash2009

I'll take a guess

at what the effect would be.  First you would hear the sound of air, rushing in to the boiler through the valve you just cracked.  Then maybe the whoosh of water returning, followed by your wife yelling "Chris, what the hell are you doing down there?"

crash2009

Seriously though

I think I might have experienced something like that before.  Check to make sure the Hartford valve is open.

ChrisJ

wife

Your really not helping, my wife yells "chris what the hell are you doing down there" at least twice a day.



Hartford valve is wide open.



I'm assuming you think the vacuum is stopping the water from returning and this is why the water level drops suddenly when the burners shut off?

gerry gill

its very possible

for a boiler to have enough steam to satisfy the radiators but not enough water content to satisfy the building..we have at times installed a reservior tank to provide extra water when the lag time is to great for the condensate to get back quickly.

ChrisJ

reservior tank

Gerry,



What kind of reservior tank do you use? I see WM recommends making one out of 8" pipe but I have no clue where to source that size pipe or what it would cost.



I wouldn't mind adding a bit of reserve to the system.

nicholas bonham-carter

reservoir tank

here is what i have made out of 2 old expansion tanks, though 1 would be enough for a small system. the horizontal center-line of the tank must be at the height of the waterline. and the top of the tank is connected to the equaliser at ceiling height.

wouldn't be nice to have transparent piping?--nbc

ChrisJ

tank

Hmm.



I think you posted the wrong pic



I'm assuming you simply remove the bladder from the tank, drill and tap the top so you can connect it in as you said?

gerry gill

we use hydronic compression tanks

that are asme rated..we put sight glasses on them..on one we 'morphed' it into a feed tank by putting a pump on it and through the use of creative thought of all parties involved we kept the gravity returns wet.

gerry gill

he's got the right tanks.

no bladder inside..old style tanks.

ChrisJ

bladderless tanks

Wjere does one find such tanks these days?

gerry gill

any plumbing supply house

or statesupply.com , do an internet search for hydronic compression tanks.

ChrisJ

tanks

Thanks guys, I appreciate the help!

Hap_Hazzard

Excuse my ignorance, but...

My tiny brain is having a hard time understanding how vacuum can keep condensate from returning to the boiler, let alone push it back out. Wouldn't the equalizer prevent this? I've heard of pressure keeping water from returning if the "A" dimension is undersize, but how can a drop in boiler pressure force water back into the return piping or even delay its return?

ChrisJ

Don't know

Being I've witnessed it a few times I've been thinking about it and the only thing I can come up with is.  The system shuts down and goes into a slight vacuum, this lowers the boiling point which keeps the boiler producing steam.  At the same time the radiators also in a vacuum stop condensing steam as fast.



This causes more water to be pulled from the boiler than when it was actually running.  Honestly though I have no clue nor do I know if that even makes sense.  I am currently running it with my gauge glass a hair below 3/4 full and watching carefully.  I don't appear to be producing wet steam.

nicholas bonham-carter

water held in the returns

think of a straw under water with one end closed by your finger. you can raise the straw up and the water will stay in the straw until you take your finger away.

in the case of your returns the vacuum comes from the collapsing steam, which is not being relieved very quickly by your main vents.--nbc

ChrisJ

water going byebye

Nicholas,



Should I be concerned about this or does it not matter?

ChrisJ

tricocks

I noticed this boiler was avaliable with tricocks as an option.  Though the block does not have tapings for it, I can see the knockouts in the side panel.  Is it safe to suggest this boiler can be run with the NWL about as high as the upper tricock or is that a poor assumption?



Why would you want tricocks over a gauge glass, or are they used together?

Jean-David Beyer

Why would you want tricocks over a gauge glass

Belt and suspenders?



On a steam powered railroad locomotive, you want tricocks (all three of them, sometimes 4) so if the gauge glass gets broken, you do not have to drop the fire and stop the train.

Hap_Hazzard

Where's the finger?

I understand the analogy, but I don't see what's keeping the other end of the "straw" closed. If the straw is the return loop, it goes back to the main, which goes back to the riser and header, then to the equalizer, through the Hartford and back to the return. I keep going through this in my little mind and I don't see anything that would prevent the water from seeking its own level. If the cooling radiators are creating a partial vacuum, I don't see it affecting one end of the water column more than the other.



I bet you'd be glad to show me the finger right about now. :-)

crash2009

Chris

I just wanted to throw something out there for discussion.  As you know you and I have very similar boilers EG45 and EG55.  You have been experiencing some unusual water problems.  You know that I am no boiler expert, as a matter of fact, you know more about putting one together than I do. 



I do know that the steam comes out of the boiler, through our dropheaders, then rises into our systems.  At the same time the dropheader is separating the water from the steam and forcing the water back into the boiler through the equalizer.  This equalizing action sucks the condensate from the wet return through the Hartford Loop.  I don't know for sure if it makes a difference or not, but I noticed that your equalizer drops down and goes around the boiler and comes in the other side.  Exactly like Figure 18, from the Weil McLain manual.  Please note there is only one boiler riser in the Figure 18 example.



Mine and many others that I have looked at that have 2 boiler risers equalize on the left side of the boiler instead of the right.  Mine is piped like the EGH example in picture 2. 



I am curious to know if it makes any difference in the operation of the equalizer/hartford, which side of the boiler the equalizer returns back in.  And if it does make a difference, would this cause some of the problems you are having, such as the wet steam up into the stair radiator, and these low water conditions back at the boiler.

crash2009

I'll take a guess.

I think the straw is the first riser off the main, the wet radiator, up the stairs.  Chris reported it being wet a while back.   

ChrisJ

equalizer

Crash,



I've actually had 3 or 4 of the Hoffman 1A's become 'wet" randomly now. Running a 2 degree setback seems to avoid it as the system gets to heat up real good. This evening I did a 3 degree increase which ran at 1/20th of a psi at peak and had a total run time of 30 minutes.



The Hoffman 1A's hold water in the bottom, no matter what its part of the design. Why randomly I get a small bit of water in the orifice of a random vent I'll never know. Increasing my temperature 2 or 3 degrees is enough to both cook, and dry the vents out though.



After skimming a while back my water line is very steady and my pressure gauge, if it registers anything like it did tonight is dead calm.



I ordered all Gorton vents for my neighbor. I'm going to see how they perform compared to the Hoffman's. Something tells me I'm going to like them more.



The wet vents kind of annoy me, but the low water condition is what really confuses me. With my NWL increased some I didn't run low on water after it shut down from the 3 degree recovery.

Hap_Hazzard

So then...

If he shuts the valve to that radiator the water level won't fluctuate as much? But why would the water accumulate there?

crash2009

Test

First riser takeoff is kinda flat.  Not on a 45.  As a test, shutting the valve might confirm.



I was just taking a long-shot.  Equalizer not circulating.  Wet steam shot up the first riser.  Steam collapses in radiator creating vacuum.  Vacuum holds water suspended in riser 1.  I am stretching my imagination too much.  My head hurts!

Hap_Hazzard

When you take those long shots...

You seem to hit something more often than not. I've learned to take your hunches seriously.

ChrisJ

Na

I have that radiator venting real slow now and it behaves nice.  It heats up nice and slow until the whole thing is hot and the vent snaps shut.  Though like all of the other radiators in the house the ONLY time that vent even gets warm is during recovery in the morning.



I have two radiators which are still not pitched correctly,  one is 11 section 30 EDR and the other is 19 section 50 EDR.  They both behave fine and are quiet most of the time.  The only time I heard noise from one of them was on a 3 degree recovery when it was 8F outside the 30 EDR one was bubbling and wooshing at 5:30AM.  That was when I made a note to fix the pitch.  Could those two radiators being pitched wrong hold more water during a long run than a short run?  I would think once its full enough to drain it would maintain one level.



I realize I need to fix them, I just haven't gotten around to it yet.  I fixed the pitch on the ones which were giving me obvious headaches.

Dave in QCA

Observations

Chris,  I am not a boiler expert and I am not sure what is going on in your system, but here are some thoughts.



1.  Your boiler has a very low water content, only 9.8 gallons to the NWL.  It would be nice if they would make the castings a little bit bigger so that there is more water content and minor fluctuations because of condensate return times would not be an issue.  Hi efficiency does not require low water content, there are examples out there that prove that, although I'm not sure if they exist in the smaller residential models.  Weil-Mclain recognizes that low water content can be a problem on this boiler when condensate return time is slow.  The actually show a return water reservoir setup on page Page 16 of the Installation Manual.  Of course, this has been discussed in detail in previous posts with some very good examples of similar reservoirs constructed to compensate for low water content boilers.



2.  Your header and all of your steam mains appear to be uninsulated.  This will make a difference.  During the initial heating stage, mains will be wet and condensing water whether insulated or not, but an insulated main will come up to temperature and the interior surfaces will dry off because the pipe is able to come up to temperature and the heat loss is slow enough that the surfaces will remain dry.  When you add up all of your mains and figure condensation forming on the inside surfaces, this would be a measurable amount of water.  how much?  dunno.  Maybe not enough to make a difference, but it could be a factor.  But your radiators that are pitched bad enough that the cause a whooshing and bubbling sound when they are running... that is another story.  It sounds to me like the incoming steam is causing the condensate to pile up in the radiator.  Once the boiler shuts off, it can finally drain back to the boiler, but it probably takes a few minutes to get back there.  In the mean time, you could have a lot of condensate hiding in the radiators.



3.  It should not make a difference which side your equalizer returns to the boiler when you have two risers.  While your return piping and equalizer appear to be, "creative" it should not pose a problem.   The equalizer actually does not suck the water in from the return lines, but rather, as the water level rises in the return lines where the dry returns drop down to the wet return, the force of gravity pushes the water into the equalizer line whenever the level in the return drop is higher than the NWL in the boiler, minus pressure drop and Dimension B factors, which may allow the condensate to stack up a little bit, but it still is the force of gravity in the return drops that push the water through the return piping and into the boiler.



4.  Boiling water raises the water line.   Huh?   Yes, it is a factor that I can see on my boiler as well.  It is a big ole Pennco cast iron sectional, has about 47 gallons of water in it.  When it is boiling, the the water level is about 1/2-1" higher than when the fire shuts off.  Think about boiling water.  The bubbles of steam are not just on the surface.  The bubbles of vapor are being formed all throughout the vessel  and as they are present under the water line, they will be displacing a little bit of water, causing the actual water line to rise.  If you could see inside the boiler, you'd see a vigorous rolling boil at the water line.  You can't see that in your site glass, but the glass DOES indicate that the water line is a very little bit higher then when you shut the burner off.  The water line will drop very fast, much quicker than it takes for any vacuum to form.  Vacuum has nothing to do with it.



5.  Wet vents.... ugh.  No great thoughts on that one.  The problem seems to occur with obvious cause.  For partial steaming, where the vent never sees steam, they should remain dry.  For full steaming, low pressures always help avoid spitting vents, but once steam gets inside the vent, there is going to be condensation.  The Hoffman vents seem to cycle open and closed once steam has initially closed them and that is usually when the spitting occurs.  You may have better luck with the Gortons remaining dry.

ChrisJ

insulation

Hi Dave,



The pictures Crash posted are old,  I think he likes to hide my insulating job cause its not as good as his

I'm not done yet, but have far more than I did in the beginning.



I can believe the water level dropping when the boiling stops and your measurement sounds dead on.  When It shuts off I go from 1/2" to an inch of water to an empty glass.  I'm fairly sure I'm going to end up adding a tank in the near future as I don't like barely having enough water.  Something along the lines of what Gerry and Nicholas showed me.  I just need to get some money together.

Dave in QCA

Great Job

Excellent insulation job!  It is as good or better than I could do.  Perhaps not as perfect as Crash's, but I also note that you have not painted your boiler room and set up an office in there either!  



However, I do see that you have put the cover back on your electrical panel.  I was going to lecture you on that.... good thing I didn't, I'd have even more egg on my face!

Ron Jr._3

Gerry and Dave are on to something

Actually this phenomenon happens alot with our installs. After steaming for a while the water level gets low in the sight glass. When the burner shuts off the remaining water just disappears in a flash. I think it has more to do with the lower water content boiling out faster than if the level was higher. If it was vacuum the water would have to be sucked up into the return piping. Which does not happen when were flushing the returns at the same time and have the ball valve shut to purge the returns.

ChrisJ

electrical panel

The panel cover was only off because I had a 20 gallon water heater wired in temporarily while I waited for them to run the gas line to my house.  I didn't want to knock an extra spot out for a breaker that wasn't staying.  It wasn't pretty but it got the job done.  When the first picture was taken I was to the point where the new water heater was mostly piped in.  I had cut the temporary inlet line to the 20 gallon heater and was using a washing machine hose to feed the 20 gallon heater from the new heaters drain.  When I ran the new cold water line from the meter I didn't want an 'extra' spot for the temporary heater left capped.  Once the gas was on I simply tore that little 1/2" hot water line out and piped in the new heater with 3/4" and fired it up.  Second picture is of the 50 gallon heater plumbed in and running.  The small temporary was still sitting there at the time.



Three adults managed to live in a house together for 2 months with nothing more than a 20 gallon 120V water heater .  



The previous setup used a hot water coil in the oil fired boiler. 





There were times over that period of 2 months where I had wished that cover was on, such turning around in the basement with long lengths of pipe near the panel.

Mark N

Just A Thought

If the water drops as low as the bottom of the sight glass, it looks as though the water level is below the level of the Hartford loop connection to the equalizer. When this happens is it possible the returning condensate can't get back into the boiler till after it stops steaming. I would think if the level of the water dropped below the loop connection the pressure in the equalizer might keep the condensate from returning.

Hap_Hazzard

I can see that, but...

He said his low-pressure gauge dips into the negative while this is going on. That's what's so odd about this.

nicholas bonham-carter

Checking for vacuum at vents

It may be safer to put on a temporary ball valve in place of one of the main vents for vacuum detection. You would then fire the boiler until all the rads were filled with steam, and after turning off the boiler, open the vent-valve. A strong vacuum should show itself pretty soon.

I imagine that the vents are lagging in their vacuum relief. Maybe a check valve would relieve the vacuum more effectively.--NBC

ChrisJ

vacuum

Wouldn't installing a check valve to release vacuum be counter productive?

I thought a vacuum was a good thing, just hard to maintain in a single pipe 80+ year old system?

nicholas bonham-carter

vacuum

vacuum has it's place, but in your case, it seems to be unequal enough to be holding the water up in the return, and this test will check whether the water drops, when the valve is opened. a true vacuum system would have such an equally distributed vacuum, that the water would not be held up.--nbc