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Pressure in gauge stays high after heating cycle ends

Ori
Ori Member Posts: 36
Hello,
I have a one pipe steam system, with EG-50 boiler (446 EDR, 142,000 DOE), connected to 292 EDR. Most of the rads are on the third floor apartment, and only few are in the basement (there are no longer radiators on the 1st or 2nd floors -- their risers are capped).
I believe there is more than adequate main venting capacity: on the 3" main there are two big mouths and one Gorton #2, and on the 2" main there is one big mouth and two Gorton #2. There are a total of 14 rads, most of the rads are using Maid-o-mist #4 and few #5.

Both the vaporstat (0-16oz) and the gauge (0-18oz) are sitting on a single pigtail, that is connected to a snubber (#32618 Ray Porous Snubber 1/4" NPT Brass 5000psi (Air, Steam, Gas)). The vaporstat is set to cut out at 4oz, and back in at 2oz, BUT after a heating cycle is over, stops on pressure by the vaporstat, the gauge shows the pressure remains elevated for a long while (over three hours), even though the main vents open within about a minute after the boiler stops.
In fact, the pressure further increases from 4oz (when the vaporstat stops the boiler) to about 6oz, before it starts its long decent down to zero. This, of course, prevents the vaporstat to reset, which in turn, prevents the boiler from keep working till the tstat is satisfied. Furthermore, when the gauge finally shows zero pressure (after several hours), the vaporstat still doesn't reset, but resets only after few hours more...
I've changed vaporstat, but same problem.

Both the pig tail and Tee are cleaned. I tried a different snubber before (1/4" Brass SSN Water Snubber, 10,000 PSI) but had the same problem.
Unfortunately, a snubber must be used because of the low setting of the vaporstat, otherwise a random pulse of pressure would stop it prematurely.

Any idea what might cause it?

Additional information: it takes about 10 minutes to get the header hot from a cold start, and about another 8 minutes for the vents on the two mains to close (the 3" main vents close about a minute before the 2" main vents).
It runs on 2-3oz of pressure for about an hour, till all the rads' sections are fully hot, and then takes another 15 minutes to raise to 4oz, when the vaporstat stops it.

Is it reasonable to wait an hour for the rads to be fully hot (from cold start)? or perhaps I'm using too small rad vents (#4), and should increase them for faster heat? (but then some will not start heating at the same time...).

Another question please:
In one place in the basement I'm using two wall rads, connected in series (see pics). Those rads are below the steam mains. In order to facilitate that, I have a new drip line (3/4" copper, buried in the floor) that goes to the boiler wet return. So those two wall rads are essentially a two-pipe system. Both rads are getting hot, and so is the copper drip line by rads.

Do I need to install an inverted bucket or steam trap between the bottom of the lower rad and the drip line? I think that without it the steam just condenses back to water upon reaching the water in the drip line, thus wasting energy. Note that the boiler water line is only few inches below the bottom of the lower rad... Please see attached pic.

Thank you for your help.


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Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,097
    No need for a trap on those rads it will do nothing.

    I suspect your pigtail, or some fitting (snubber should be removed) is plugged, or the gauge is bad. The boiler can't hold pressure that long. Your boiler has plenty of capacity. Something is out of wack. With the boiler capacity you have you should be cycling on pressure (not that you want to) but it shows the system is not heating quickly
  • Fred
    Fred Member Posts: 8,540
    Where is the pigtail connected to the boiler? Is it on a manual LWCO or directly into a boiler port? In either case, while the pigtail may be clean, the opening at the LWCO especially the McDonnell Miller #67) or into the boiler may be clogged. If the vents open, it can't hold pressure in the system. It has to be at the Vaporstat or its pigtail connection(s).
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    Snubbers can be very useful -- but it's not at all unusual to have them give just the sort of trouble you are having. Further, while I applaud the low vapourstat setting, it's perhaps too low. I'd try setting it at 7 ounces or so and taking the snubber out.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ori
    Ori Member Posts: 36

    Snubbers can be very useful -- but it's not at all unusual to have them give just the sort of trouble you are having. Further, while I applaud the low vapourstat setting, it's perhaps too low. I'd try setting it at 7 ounces or so and taking the snubber out.

    I'll raise it to 7oz and will take the snubber out as suggested. But wouldn't it cause the boiler to work an extra 10-15 minutes or so each time? Integrate that over the entire heating season, and you end up with hours, if not days of extra heating time...:)
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,041
    edited November 2022
    Get rid of the snubber. What's that about? Increase the pressure differential and setting if the control's making/breaking repeatedly. I suspect it's unreasonable for that control to operate dependably in a 2-ounce range.

    The radiators should heat fully in less than an hour. If condensate handling and firing rate are not problems, consider larger radiator vents, at least on the big radiators.

    You need some more venting on the 3rd floor either atop the riser(s) or on the radiators and you may have to slow down the basement radiators.

    Are you sure the basement radiators aren't filling with condensate from the return? Remember that the water level in the return will be higher than the boiler. They seem pretty low and condensate may be backing into them dramatically increasing your system's water content...

    Just some thoughts to consider.
  • Ori
    Ori Member Posts: 36

    No need for a trap on those rads it will do nothing.

    I suspect your pigtail, or some fitting (snubber should be removed) is plugged, or the gauge is bad. The boiler can't hold pressure that long. Your boiler has plenty of capacity. Something is out of wack. With the boiler capacity you have you should be cycling on pressure (not that you want to) but it shows the system is not heating quickly

    I always felt that this system takes too long to heat, given its capacity vs connected rads. In fact, the cost of heating only the 3rd floor (and very few rads in the basement) is very similar to heat another 3 floor apartment of a similar size, that I service.
    I looked at the chimney while the boiler was working and didn't see any leak of steam, nor from the boiler itself or in any of the other two floors, that currently don't have any rads (their raisers are capped). Is there a way to pressure-test the pipes in the building for a leak? I could close off all rads floor valves, and if was possible, pressurize the system to inspect for leaks. Possible?
  • neilc
    neilc Member Posts: 2,084
    post a more distant picture of the Vstat, pigtail, and boiler connection, showing them all in one shot,
    known to beat dead horses
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,041
    edited November 2022
    You can fill the boiler up to the header to determine if it's leaking steam above the water line. You can cap the radiator vent tapings and pressurize with air to look for piping leaks.
  • Ori
    Ori Member Posts: 36

    Get rid of the snubber. What's that about? Increase the pressure differential and setting if the control's making/breaking repeatedly. I suspect it's unreasonable for that control to operate dependably in a 2-ounce range.

    The radiators should heat fully in less than an hour. If condensate handling and firing rate are not problems, consider larger radiator vents, at least on the big radiators.

    You need some more venting on the 3rd floor either atop the riser(s) or on the radiators and you may have to slow down the basement radiators.

    Are you sure the basement radiators aren't filling with condensate from the return? Remember that the water level in the return will be higher than the boiler. They seem pretty low and condensate may be backing into them dramatically increasing your system's water content...

    Just some thoughts to consider.

    That's why I thought that perhaps an inverted bucket is needed between the return of the lower rad (bottom left of lower rad) and the drip line, to prevent the water from the drip line to enter the rad...Or it won't help?
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,041
    Forget adding traps and consider the system problems I mentioned.
    bburd
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,041
    edited November 2022
    Ori said:

    I'll raise it to 7oz and will take the snubber out as suggested. But wouldn't it cause the boiler to work an extra 10-15 minutes or so each time? Integrate that over the entire heating season, and you end up with hours, if not days of extra heating time...:)

    Once the system is filled with steam the metal is hot and the vents are closed, pressure should increase very quickly, almost instantly. Get the thing to work first and then consider the efficiencies.
  • reggi
    reggi Member Posts: 312
    All the right answers already so maybe a few photos of setup to eliminate any guesswork ..
    Now with the radiators removed from the the first and second floors you'd expect to have some short cycling but you aren't..
    I'm thinking the snubber is letting air in, but not out and the air is building up slowly in the Vaporstat... like filling a balloon.. but it's rising by the heat of boiler running and anything trapped above the snubber is expanding causing the needle to rise, hence why it takes so long to come down after it turns off....it has to cool down and condense.... just put a "T" above the snubber and a valve then when it goes over 4,,,oz and doesn't drop you can open the valve and see if that's the solution...
    Elsewise there could be a problem with the Vaporstat Diaphragm..
    Remove as a unit and blow into the inlet and there should be little effort to get it to "Click".... now if it doesn't you'll have to blow a bit harder but be careful because the Diaphragm could be waterlogged and and all that water will try coming out where your blowing in....
    Pretty simple 
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    Two thoughts. First, it won't take very long to go from 4 ounces to 7 ounces -- you'd be surprised. As has been said, once those vents close and the pressure starts to build, it goes up quite quickly. So that's not a problem.

    Second, the quickest slickest way to check for leaks is to keep track of how much water you have to add. Ideally, you shouldn't have to add any. In practice, anything more than a gallon a week is cause to start looking around.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ori
    Ori Member Posts: 36
    reggi said:

    All the right answers already so maybe a few photos of setup to eliminate any guesswork ..
    Now with the radiators removed from the the first and second floors you'd expect to have some short cycling but you aren't..
    I'm thinking the snubber is letting air in, but not out and the air is building up slowly in the Vaporstat... like filling a balloon.. but it's rising by the heat of boiler running and anything trapped above the snubber is expanding causing the needle to rise, hence why it takes so long to come down after it turns off....it has to cool down and condense.... just put a "T" above the snubber and a valve then when it goes over 4,,,oz and doesn't drop you can open the valve and see if that's the solution...
    Elsewise there could be a problem with the Vaporstat Diaphragm..
    Remove as a unit and blow into the inlet and there should be little effort to get it to "Click".... now if it doesn't you'll have to blow a bit harder but be careful because the Diaphragm could be waterlogged and and all that water will try coming out where your blowing in....
    Pretty simple 

    I think that's indeed the case: the snubber lets the air in, but not out.
    I uninstalled the gauge while it was showing 6oz pressure, a while after the heating cycle and the boiler was off, and heard the trapped air escaped, followed immediately by the gauge needle dropped to zero. So it's the air trapped between the gauge/vstat T and the snubber on which the T sits.
    But that was the case with two different snubbers as described in my original note. So is it a coincidence that two snubbers are faulty (if so, is there a way to fix the snubber to let the air out?), or it's a case where a snubber shouldn't be used at all, as suggested by others in this post?
  • reggi
    reggi Member Posts: 312
    Ori said:
    All the right answers already so maybe a few photos of setup to eliminate any guesswork ..
    Now with the radiators removed from the the first and second floors you'd expect to have some short cycling but you aren't..
    I'm thinking the snubber is letting air in, but not out and the air is building up slowly in the Vaporstat... like filling a balloon.. but it's rising by the heat of boiler running and anything trapped above the snubber is expanding causing the needle to rise, hence why it takes so long to come down after it turns off....it has to cool down and condense.... just put a "T" above the snubber and a valve then when it goes over 4,,,oz and doesn't drop you can open the valve and see if that's the solution...
    Elsewise there could be a problem with the Vaporstat Diaphragm..
    Remove as a unit and blow into the inlet and there should be little effort to get it to "Click".... now if it doesn't you'll have to blow a bit harder but be careful because the Diaphragm could be waterlogged and and all that water will try coming out where your blowing in....
    Pretty simple 
    I think that's indeed the case: the snubber lets the air in, but not out. I uninstalled the gauge while it was showing 6oz pressure, a while after the heating cycle and the boiler was off, and heard the trapped air escaped, followed immediately by the gauge needle dropped to zero. So it's the air trapped between the gauge/vstat T and the snubber on which the T sits. But that was the case with two different snubbers as described in my original note. So is it a coincidence that two snubbers are faulty (if so, is there a way to fix the snubber to let the air out?), or it's a case where a snubber shouldn't be used at all, as suggested by others in this post?
    Try blowing through each end of 10,000 lb snubber @JamiJamie Hall" could tell you more about snubbers as he uses (d) them before moving his setup and  @Fred could tell you about how quickly they could get gunk from the brown water and turbulence of the 67 LWCO flush and test ( Plus your's looks way cramped up in the pip you posted.... don't be shy... you'll always get good advice here... 
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • Ori
    Ori Member Posts: 36
    reggi said:


    Ori said:

    reggi said:

    All the right answers already so maybe a few photos of setup to eliminate any guesswork ..
    Now with the radiators removed from the the first and second floors you'd expect to have some short cycling but you aren't..
    I'm thinking the snubber is letting air in, but not out and the air is building up slowly in the Vaporstat... like filling a balloon.. but it's rising by the heat of boiler running and anything trapped above the snubber is expanding causing the needle to rise, hence why it takes so long to come down after it turns off....it has to cool down and condense.... just put a "T" above the snubber and a valve then when it goes over 4,,,oz and doesn't drop you can open the valve and see if that's the solution...
    Elsewise there could be a problem with the Vaporstat Diaphragm..
    Remove as a unit and blow into the inlet and there should be little effort to get it to "Click".... now if it doesn't you'll have to blow a bit harder but be careful because the Diaphragm could be waterlogged and and all that water will try coming out where your blowing in....
    Pretty simple 

    I think that's indeed the case: the snubber lets the air in, but not out.
    I uninstalled the gauge while it was showing 6oz pressure, a while after the heating cycle and the boiler was off, and heard the trapped air escaped, followed immediately by the gauge needle dropped to zero. So it's the air trapped between the gauge/vstat T and the snubber on which the T sits.
    But that was the case with two different snubbers as described in my original note. So is it a coincidence that two snubbers are faulty (if so, is there a way to fix the snubber to let the air out?), or it's a case where a snubber shouldn't be used at all, as suggested by others in this post?

    Try blowing through each end of 10,000 lb snubber @JamiJamie Hall" could tell you more about snubbers as he uses (d) them before moving his setup and  @Fred could tell you about how quickly they could get gunk from the brown water and turbulence of the 67 LWCO flush and test ( Plus your's looks way cramped up in the pip you posted.... don't be shy... you'll always get good advice here... 

    Interesting! I tried to blow air but wasn't able to from either side! Does it mean it's clogged? But it's still lets the air in...
    In the instructions they suggest to use 'Commercial Grade Solvent', I'll try that.
    By the way, is there any filter to put before the snubber, so won't get gunk and clogged?
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    I did have a snubber on Cedric's vapourstat when it was mounted in a conventional way (pigtail off boiler). It clogged. So did it's replacement. A matter of months. Not that they failed, they clogged and there is no good way to unclog them. I cured the problem completely by tapping a mount on the header and put it there. No snubber, isolated from the pressure surges from bubbles.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ori
    Ori Member Posts: 36
    Found this related post on The Wall; that's probably what it is -- a clogged snubber that causes the pressure to stay elevated after the boiler shuts off...:

    "There is a brass hexagonal extension between the gauge and the boiler, which is really a snubber, I believe. If you remove this, from the boiler and the gauge, you will undoubtedly find that you cannot even blow through it! Probably your gauge takes a loooooong time to go back to zero after boiler stops firing, right? If you now take a very small straight pin and start scraping around in the annular space at the boiler end of the snubber, you may find a very small hole which is kinda at an angle to the snubber, in the annular ring. You should eventually be able to poke the pin through this hole and remove the clog. Your gauge will now be back to factory showroom performance. Kinda like trying to measure a flea with a yardstick!"
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,097
    I agree with @Long Beach Ed The radiation is too low and condensate may back up in them but so what? They may be heating with steam at the top and water at the bottom. Traps and check valves will not fix this.

    Your boiler capacity may be off. I would check the gas pressure on the burner manifold should be 3.5" of wc give or take. Maybe have the combustion checked. The boiler is oversized for the load something is amiss. It should not be that slow to heat plus your pressure is low, you should have higher pressure than you have (not that you want that but it shows lack of boiler capacity. As far as leaks go how much water are you adding?
    Long Beach Ed
  • reggi
    reggi Member Posts: 312
    Is this set-up... with the 1st  and 2nd floor risers capped off "NEW"  along with the removal of the radiators on those floors?
    I'm not that familiar with one pipe systems so I'd have to think the 3rd floor would have to piped that it wouldn't be affected by the changes in the piping below it as that is now the system and must function as such...In other words did capping off the 1,2nd floor cause a disruption to the operation of the system for the 3rd floor and are these the problems ( oversized boiler now) your trying to address with the snubber and Vaporstat  ? 
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
    MikeAmann
  • JUGHNE
    JUGHNE Member Posts: 10,278
    I had a lot of "giggle" in the HG of this vaporstat......close to tipping it off early.
    The double pigtail solved it, settled down gauge needle flutter also.

    It is installed where the original 0-30 syphon gauge was previously.
    Keeps it up out of any water.



    MikeAmann
  • Ori
    Ori Member Posts: 36

    No need for a trap on those rads it will do nothing.

    I suspect your pigtail, or some fitting (snubber should be removed) is plugged, or the gauge is bad. The boiler can't hold pressure that long. Your boiler has plenty of capacity. Something is out of wack. With the boiler capacity you have you should be cycling on pressure (not that you want to) but it shows the system is not heating quickly

    I removed the snubber as suggested, yes it solved the problem; the snubber probably did let air in (was able to read pressure) but not out, so the pressure stayed elevated for a long time.
    So, I'm left with one important problem: as mentioned, it takes the system quite a long time to heat given its capacity: 50 minutes or so to get all the rads fully hot, sometimes more, depends if on the weather, and if it's a cold boiler start.

    As a reminder, the boiler is input 175k, DOE of 142k (steam sqft 446), connected to 300EDR.

    I don't add water (so no leak is apparent, nor any steam visible in the chimney). As said, most of the rads are on the 3rd floor, and only few are in the basement. I also increased the venting from #4 to #5 and #6, yes it did shorted a little the heating time, but not by much.
    This three story building used to have rads on each floor, but now all the raiser are capped, expect on the 3rd floor, where they have radiators.

    The when boiler starts, between the time the header gets hot and when the main vents are closed (about 7-8 minutes), the needle of the 0-18oz pressure gauge shows about 3oz, and after the mains close it stabilizes at around 2oz. If not stopped by the tstat, after an hour or so the pressure builds further, and the vporstat stops the boiler at 5oz (no need to set it higher, as all rads are fully hot at that point,) and then short cycling begins. I intend to mitigate that by installing a 20 minutes timer delay.
    Plenty of main venting capacity as mentioned at the top of this note.

    Given that the boiler is about 50% (?) oversized, I'd expect the rads to get fully hot a lot quicker.
    Do I need to order a (probably pricy) combustion and gas pressure test, or is there anything else suggested I test before that?
    Please see additional pics of the boiler here.

    Last, I'm using Nest thermostat. I know is suboptimal when it comes to steam, but it's very handy to keep track of heating times, accommodates several temperature sensors, and has a good app. However, it does allow for 1 degree differential, and I observe 3 degree range around the set point (set to 69, and observe 68-70). It does NOT have ability to control CPH, and that's a major drawback.
    Is there a thermostat you recommend that is able to effectively (and efficiently) control steam system (steam only, for cooling they have a different thermostat), with ability to control CPH (I used to set it at 2 with the older non-wifi tstat), ability to have multiple temperature sensors, and a good app to monitor on the phone? Ecobee does not have the CPH that i'm after, for more stable temp.
    Please advise.
    Thanks
  • bburd
    bburd Member Posts: 576
    edited December 2022
    You may need to vent the tops of those third-floor risers, or add second vents to the radiators in the upper tappings, to get them to heat quickly. If the radiators that were removed on the lower floors were connected to those same risers, air is no longer removed at those levels.“the lost art of steam heating“ discusses this.

    Also, are all your steam mains  insulated? This will make a significant difference.



    Bburd
  • Ori
    Ori Member Posts: 36
    I think the 1st floor had their own sets of risers, but likely the 2nd and 3rd share the same; at least that's how it looks from the piping at the basement ceiling. So yes, I believe that the 2nd floor former rads (now capped) where sitting on the same raiser with the 3rd floor rads.

    Most of raiser of the rads on the 3rd floor are getting hot within 10 minutes from the time the main vents close. Some even after 10 minutes, so perhaps it's indeed a venting issue.
    Do you mean adding vents (say Gorton #1) on the raiser before the floor valve, or after the floor valve but before the rad?

    Also, the 2" main is completely uninsulated as I'm using it to heat several rooms in the basement area, where there isn't a tapping for a ceiling rad...
  • Ori
    Ori Member Posts: 36
    I found out how to vent the raisers on the 3rd floor (see pic attached). I'll try that...
  • bburd
    bburd Member Posts: 576
    edited December 2022
    Ori said:
    I found out how to vent the raisers on the 3rd floor (see pic attached). I'll try that...
    Yes, that’s what I meant. It’s usually only necessary in buildings more than three stories in height, but your case is unusual.

    The uninsulated main will certainly slow the steam to the third-floor, but I understand why you are leaving it that way.

    Bburd
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    It would appear from your comments that things are working reasonably well. It is important to remember that the boiler capacity -- provided that it is adequate to heat the radiators fully, which yours is -- has very little to do with how rapidly a space will change temperature. That's governed by the capacity of the radiator in that space. So changing the boiler's capacity won't help -- and I see no need to check it further (other than normal maintenance, of course!)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ori
    Ori Member Posts: 36
    Just to better understand, are you suggesting that about 50-60 minutes is reasonable time for all rads to be fully hot in general, and also specifically to this oversized boiler? (Yes, I understand that it's different than changing the temperature of a room, which is dependent of the capacity of a radiator).
    Anyway, I'll add riser venting and see if further improves.

    Any recommendation of a wifi tstat that accommodates several sensors, has CPH choice, and a reasonable app for iphone?
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    I admit it does seem a bit long... although Cedric does take about 45 minutes to get his system fully hot.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ori
    Ori Member Posts: 36
    I removed the snubber as suggested, but now violent pressure develops right at the beginning, caused the vaporstat to stop the boiler after reaching 6oz. It happened during the first 2 minutes after the boiler start, while the main vents aren't closed yet (2 bigmouth and Gorton#2 on 3" main, and 1 bigmouth and 2 Gorton#2 on 2" main); Please see a 30 second video, where it stops at the end. You can hear the air being pushed through the main vents....
    https://youtube.com/shorts/cV8h8uMX2jY?feature=share

    Is it normal to have such (relatively) high pressure right from the start, or it's an indication of some blockage?
    By the way, if it isn't as violent at the beginning and the vstat doesn't stop it, it usually stabilizes at around 2oz after the main vents close.

    Also as suggested, I installed a T and a straight gate valve before the radiator, that is in order to vent the riser that comes to the 3rd floor (as mentioned earlier, the lower floors don't use any radiators, --only the 3rd floor have them, and few in the basement). Please see pics attached. Is that the right way to do that? If so, I'll do the same for the other risers...
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    No, that isn't normal. I wonder if the boiler needs a good skim?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • reggi
    reggi Member Posts: 312
    Watching your Gage gave me a perhaps a "ahaa" moment.. Since last year you capped off the 1st floor risers, the second floor we're already capped off.. and with all this other work on system have you skimmed it flush any oils that may of been introduced to your system ? Flushing and blow downs won't clear oil... they just create a barrier that the steam/vapor needs to punch through ( others can correct my terminology ) until the tension is broken and then your pressure stabilizes ... Until the next time when oils drain back or settle back and it repeats.. Skim
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • 109A_5
    109A_5 Member Posts: 477
    Hello @Ori,

    I think you will find someone went out of their way to connect your pigtail to the worst place on that boiler for what you are trying to do. Probably it is very near the place where the most pressure changes occur (Red circle). You can mellow it out without an orifice by some of the techniques mentioned above. Or maybe try this. You need more water between the steam and the Gauge / Vaporstat. The micro changes in pressure cause by the boiling on the steam side of the water line can't push around a bigger slug of water as easily (not much water in the pigtail). Also maybe moving it to a less violent location. I would tap in at the Yellow box in the picture, maybe just below the valve.

    If you look at an M&M 67 LWCO scenario with the pigtail mounted to the top of the M&M 67 LWCO. The whole M&M 67 LWCO is usually below the water line so the little bit of water in the pigtail is rarely ever expose to steam and when it is, it is much farther away from the boiling than what you have there. So the Gauge / Vaporstat would be exposed less to the impulse pressure changes.






    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • pedmec
    pedmec Member Posts: 711
    Boiler water needs to be skimmed and treated. Bouncing of gauge and rapid pressure riser mostly due to foaming of the boiler water. The foam restricts the steam from separating from the water causing bubbles on top of the water.
  • ethicalpaul
    ethicalpaul Member Posts: 4,176
    Yeah I don't buy the distance from the boiling theory...all those distances are functionally identical
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • Ori
    Ori Member Posts: 36
    Thank you! What a difference! I skimmed it; even though the water in the boiler seems clean, when I skimmed it initially, black oily water came out. I continued to skim it with tiny flow over some 22 hours...
    And, now I see only minimal pressure in the gauge; before the skim it used to move violently between 3oz-6oz before the main vents closed, now it quiet and show almost no pressure (barely moves around zero with a 0-18oz gauge, please see short video attached, of the gauge after 60 minutes of heating, right before it stopped as the tstat is satisfied).
    https://youtube.com/shorts/8cWUlbre9jE?feature=share

    As I mentioned before, it took about 45-50 minutes to raise 1 degree of temp, so I called a tech to measure the gas pressure of the boiler, wishing he can raise it so as to shorten the heating cycle, but he found that the pressure was already high: 4wc! , suggested to lower it to 3wc, said the boiler was wasting a lot of gas with such high pressure. He lowered it to 3wc. But now it takes a little longer to heat: 50-60 minutes.

    Again, given that the boiler is significantly oversized, and given that I now don't see much pressure in the gauge even after a while, and given that it takes so long to heat, what else might cause it not to build pressure and long cycles? (I didn't observe any leak nor add water, just after weekly blowdowns...
    The tech said ordering a formal combustion test of such a (relatively) small steam system won't be quite productive...
    What else can I test in order to see where all this energy is going?
  • ethicalpaul
    ethicalpaul Member Posts: 4,176
    I'm not sure why he went to 3". All the ones I have seen call for 3.5"

    I could see lowering it a bit, like to 3.3 or 3.2 if it was really oversized, but I can't figure out why to go to 3" in your position.

    But having said that, also I wouldn't worry about it taking 45 minutes to raise your house a degree. That's a lot of furniture, walls, floors and ceilings to raise one degree. If you don't want to wait for it to go up a degree, then keep it at the same setting all the time, steam works better that way anyway.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • Ori
    Ori Member Posts: 36
    the tstat set temperature isn't changing -- it's just that the Nest tstat allows for 1 degree temperature differential so it goes down one degree before the tstat calls for heat; there's no way to set CPH with Nest unfortunately...
  • BobC
    BobC Member Posts: 5,380
    The key is once the room has recovered that one degree how long are the burns it takes to maintain the setpoint? If those were 45 minutes I'd be a bit concerned but I'll bet they are a lot shorter.

    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
  • Ori
    Ori Member Posts: 36
    BobC said:

    The key is once the room has recovered that one degree how long are the burns it takes to maintain the setpoint? If those were 45 minutes I'd be a bit concerned but I'll bet they are a lot shorter.

    Bob

    I'm not sure I fully understand the question-- the Nest tstat set to 66 degrees. Calls for heat when drops to 65 (Nest allows for one degree differential), and takes about 50-60 minutes for the tstat to get satisfied (with current weather conditions). Usually the temp overshoots to 67 (one degree above set), and the next call for heat can be several hours later, depends on the outside temp and heat loss...