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Better balancing 1st and 2nd floor with 2-pipe steam, 1 zone.

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Hello, this is my first post here, but probably not the last.

I purchased a 1890 home in Maine a year ago and went through a full year of learning the heating and cooling nuances of this place. I'll try to summarize the home:

- Basement: stone foundation, 2" closed cell foam from floor to ceiling on rock.
- 1st and 2nd floor: Fiberglass blow-in insulation in the walls and 2nd floor ceiling (via attic floor) done at some point in the past few decades. No record of when.
- Attic: uninsulated, scheduled to have closed cell foam applied next month on ceiling and walls in order to renovate into a usable floor with heat pumps added for temperature control.

There is no cooling system, and the home is heated by an oil boiler connected to a 2 pipe steam system. The radiators are likely as "original" as they come, whenever steam would have been added to a home built in 1890, with evidence that there was a coal boiler that ran them before electricity was added.

Radiators all work, I have used an IR camera on them all and there are no dead segments. The valves on all but one seem to also be very old,
I attached a photo of what they look like.

I've read a bunch on the forums, I got the "we got steam heat" book, and also I got another classic book off ebay about the maintenance and operation of oil fired boilers. The boiler has been serviced and inspected multiple times, but it is VERY old (1960's American Standard... a conversation for another post).

But today as Maine gets down into the 20's at night, I want to ask the forums how I can better balance my heat. The heating works exceptionally well, but the swing between the 1st floor and 2nd floor is about 7-9 degrees, meaning if the wife and kids are downstairs at 66 degrees, upstairs where I work is 73+, and when it gets really cold down there and they want it 68, the upstairs can be 75-77 and that is too hot.

I have never closed the valves on the radiators, I am afraid that trying to operate the valves will break them as I have no record of if they have ever been serviced, and I know that valves aren't something you install 100 years ago and never touch. The home owners for the decades before me were snowbirds who left for the winter and didn't use the heating other than a little bit in spring/fall.

Is the only simple option I have to test the valves on the radiators and use the IR camera to see if closing the valves partially slows down their heating cycle on the 2nd floor? And if a valve is broken, or if operating it breaks it, is a new valve something I could repair myself?

I know that 2-pipe radiators are not the standard, I am not sure if the people who put them in this house did it because at the time it was a fancier option or whatnot, but most of the info I can find on old New England steam homes is all geared toward 1 pipe, including valve information.

Okay, long enough post for now. I know I bought a pandora's box of issues with a house and heating system of this age, so for now as things are working and I am renovating this place a project at a time, is there anything I can try to balance my heat as I continue this journey?

I have a plan to add heat pumps to all the floors as through my conversations and research, it seems I am in a bit of a bind with the boiler and system I have.

Thank you, please ask me any clarifying questions, or maybe the answer is "use the valves, and if they break or don't work, learn how to replace them."

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    The valve you pictured is characteristic not only of two pipe steam, but of a vapour (very low pressure) steam system. They were the Cadillacs of steam systems back in the day, but they are a little different... yours appears to be a Dunham system.

    First, you can partially (or completely!) close the radiator valves without harm. That, however, may be more easily said than done if they haven't been operated in a long time. You may have to start by moving the handle just a little; try both directions (clockwise will be less heat). Patience. Do not put a great big wrench on them, but you can use a lot of force on the handle.

    Second, you don't picture it but there should be a trap on the return pipe from each radiator. It is possible that one or more of these has failed over the years -- particularly if the system has been run at too high a pressure (more on that later). It's not hard to check these, however. When the system is operating at full song, the outlet pipe below the trap should be warm, like hot water warm, but it shouldn't be steam (like yeouch!!!) hot. If you have an IR thermometer, 5 to 10 degrees temperature difference between the inlet of the trap and the outlet is fine. Thing is, if a trap has failed closed, that radiator won't heat. If it has failed open, that radiator will heat well -- but other radiators on the same return will heat poorly.

    Traps can be repaired quite easily. Not to worry.

    Venting. Most of these systems used crossover traps to vent the steam mains. These were just like the radiator traps, but were connected at the ends of the steam mains to let air, but not steam, get into the dry returns. Again, they are easy to check if they are there -- the steam main up to them should be steam hot, and the dry return shouldn't be. Also most of these systems had just one main vent (Dunham called it an air eliminator...) which was located at the the boiler where the dry returns join before they drop to the wet return and the boiler. You need that.

    And at this point I might suggest -- some pictures of the boiler and the piping around it would be very helpful!

    Now. I believe I mentioned pressure up there. Somewhere on the boiler there will be a pressure control device. We need to have a photo of that. The Dunham system -- like all vapour systems -- was designed to run on a very low pressure: no more than 8 ounces or half a pound maximum pressure. If the pressure is allowed to go over that, the heating will become less and less even -- the higher the pressure, the more unequal it will be. This may be a good part of you problem, so before doing anything else find out what that pressure control device is, and what it's set for (we can help, if you get us a picture) -- and get it set for the correct pressure. It's possible that you may have to add a new one, called a vapourstat, if it isn't already there.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • seandempsey
    seandempsey Member Posts: 28
    edited November 2021
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    Here are pictures.

    Also, I had not heard of a vapour system before, but this house was a "fancy person's" build in 1890 and is covered in what at the time would have been top of the line stuff, carved wood, quarters for the maid, multiple exposed fireplaces (all retired), what appears to be coal-gas fed gaslight system in the ceilings, so it is very likely the heating system was the best they could get.

    The radiator pictured is just like all the rest, just different heights and widths and lengths,but they have the identical fittings EXCEPT for the round black one at the bottom, which I note you can still buy new.

    I did my best in the basement looking for the condensate returns, let me know if I need to go back. I know the boiler is a ticking time bomb for replacement, but so far the HVAC people who have serviced it and advised me have said while very old, it does not have any concerns yet. Fuel tank is brand new in 2019, my house does not have NG but my street does. Currently the boiler exhausts up the lined chimney (which I lined earlier this year) and I have not got a clear answer from any heating folk on what fuel (propane, more oil, NG) could power a new boiler that would properly utilize my system (no one mentioned a vapor system before this post).

    Thank you for the help. I am a diligent learner so anything I am told here I will go research and understand.

    EDIT: I got 2 more photos of the only thing I can see that relates to pressure, which is set to what appears to be less than 1psi??












































  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Oh my... i don't think it's even been messed with too badly!

    Get yourself a copy of The Lost Art of Steam Heating Revisited -- it's in the book store on this site -- and start learning about vapour systems. It's worth it. What you have is the best that a steam heating system can be -- which means it's just about the best that any system can be.

    You found the pressure switch. That's a plain vanilla Pressuretrol, and it is set for psi cutin and a cutout of psi -- which is much too high. You can keep it as a backup safety device,J but to get the best out of what that system can do for you you are going to need a Vaporstat. Honeywell L408J1009. I regret that they aren't inexpensive, but they are worth the money. Although it isn't the best place for it, you can put it on the same "pigtail" together with the existing control -- a T, two nipples, two elbows and two more nipples will do. Wire them in series (be sure to use the correct terminals on the vapourstat). Set the vapourstat for 8 ounces cutout and 4 ounces differential.

    See what that does, and then start checking for traps which aren't working and start freeing up those valves.

    On a new boiler (and yes, that one is getting a bit old, but if it's still working, keep it), any fuel source -- oil, LP, natural gas -- can be used in a steam boiler. It's mostly a matter of what is reasonably priced in your area. Since you already have oil, I'd stick with that. Properly sizing and installing a new steam boiler, however, is not something the average plumber or HVAC person seems capable of. Best to find someone who is known to be good with steam. You don't mention where you are located, but if you would, we may well know someone we can be confident of in your area, and it wouldn't be a half bad idea to get him or her over there while things are still working to get a look at the system.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    @seandempsey,

    I have a 2 pipe system and when I moved in 30 years ago it had the same problem. Mild weather warmer downstairs than upstairs, the reverse the colder it got. First, as others have said any 2 pipe system it must be balanced so that new steam arrives at all radiators nearly at the same time (1 minute or so +/- is pretty good). Pressure needs to be kept low too.

    Unfortunately doing well with both of those things did nothing for my upstairs/downstairs problem. You can run around changing valves all the time which will steer more steam up or down, but that will prove to be too much work - especially since conditions change a lot.

    I'm not sure you'd be interested but for the record what changed my system completely with regard to the upstairs/downstairs problem was natural vacuum. If you completely close up a 2 pipe system when the burner goes off and allow the system to sink into vacuum the boiler continues to make steam for a few minutes. That steam plus what is already in the mains continues to flow to radiators - something which does not happen with open vented systems. But here is the important thing - the radiators in the colder areas are condensing steam faster than the warmer areas and so those produce a slightly lower pressure inside them. The remaining steam in the mains flows then more to the colder radiators than the warm ones and evens things out. This happens each and every burn cycle. My system does 2- 2.5 cycles per hour when it is cold and that adds up to a lot of balancing.

    This has turned out to be the single biggest value of natural vacuum. It completely eliminated my upstairs/downstairs issue. I never touch radiator valves anymore. The vacuum adjusts automatically for all variations in real time, sun loads, wind loads, all of it.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • seandempsey
    seandempsey Member Posts: 28
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    @Jamie Hall thank you for so much good advice, I am copying all this to a file.

    Sort of a question I am almost embarrassed to ask: what does the vaporstat do for the system in a functional sense, and also then a usage/comfort sense? I have no problems paying qualified people to help update me, I am in Bangor Maine. The heating system works well and I plan on using it as long as it can be effectively maintained.

    I have a few more clarifying questions now:

    First, the valves on the radiators themselves, presuming they work, if I turn one partially closed, does that simply let less steam through, and thereby the radiator heats up slow and possibly doesn't get to full temp before the thermostat turns off the boiler and steam stops? Or does it need to be completely closed to cut of all steam, since eventually the radiator would reach heat saturation if the boiler ran on long enough? And if the valve is closed, does the steam just build up in the pipe, hit the closed valve, and eventually flow back down the pipe when it condenses the way it came? Is this okay in a 2-pipe system where the water is supposed to go back down the return line?

    The other things I think I mistakenly wasn't clear about was the concept of "balancing" the 2 floors (which I think is what @PMJ was referring to). The radiators all heat up together and all function well, I took IR pictures of all of them at heat and verified the pipes, valves, traps, and all of the radiator segments. So that is good, but since the radiators all do work so well, the hot air from the 1st floor rises to the 2nd floor just by way of convection, and I don't really know how to keep the 1st and 2nd floor closer to each other, or if really it's just about partially closing some of the valves on the 2nd floor radiators and not allowing them to heat as quick, and letting the convection from the 1st floor rise up.

    Convection is working against me as all the warmth gets trapped upstairs.

  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Two pipe vapour systems are, as I have hinted, a little odd. One of the oddities which I didn't hint at is that that pressure I mentioned -- no more than 8 ounces -- is actually the pressure differential between the steam main and the dry returns. I try to avoid bringing that up because it seems to be very confusing...

    Now, having said that, the effect of partly closing a radiator's valve is actually quite simple: it reduces the rate at which that pressure difference can force/allow whatever steam into the radiator. That rate is directly proportional to the area of the opening and to the square root of the pressure difference.

    The amount of heat given off by a radiator is directly proportional to the rate at which steam is allowed to enter the radiator.

    I might add that some of the radiator -- near the inlet -- will get just as hot as before with a partly closed valve. What will happen is that less of the radiator will get that hot, not that it will get hot slower.

    Changing the valve opening won't affect how fast steam gets to the radiator in the first place, or more accurately will change it very little.

    Even if the system were to fire all day long, the amount of the radiator which gets hot will not change, and therefore the heat given off will not change.

    I might note that some systems used carefully calibrated orifices instead of setting the valve openings, for the same purpose. The advantage of the valve being that you can close it further if you want to cool a space off.

    Now what a vapourstat will do for the system is simply ensure that the pressure differential is maintained at that low value, but it can only do that if the dry returns are held at or very near atmospheric pressure, since what the vapourstat is sensitive to is the pressure differential between the steam inside it (well, more accurately, the air inside pressurized by the steam acting on the pigtail, but that's a detail) and the atmosphere outside it.

    Bottom line. First, you are working with a pressure differential, not an absolute pressure, so make sure that the dry returns are well vented to the atmosphere. Second, if a radiator is too enthusiastic for the room in which it is located, close the valve partly until you are happy with it.

    Now for one bit of bad news. Bangor -- and Maine in general -- seems to be really short on people who can understand how any steam system works, never mind vapour. Not that aren't a lot of good craftspeople, it's just that they aren't familiar with it. Therefore... you are going to need to become the expert. Don't panic -- it's rather fun and not that hard.

    OK. Now for a bit of history, to which you need not pay any attention at all if you don't want to. When your system was installed, it almost certainly was coal fired. You can't turn coal on and off like an oil burner. Therefore, it was also almost certainly equipped with a very sensitive device which sensed the pressure differential between the steam main and the dry returns and acted to keep that differential at the desired value. There were a variety of these widgets, and some systems had more than one type. Generally speaking, the resulting combustion efficiency was pretty horrible, as what most of them did was to reduce the draught on the fire so it just smoldered if the differential got too much. 100 years ago, no one cared... Some systems also allowed the dry returns to drop into a vacuum if the fire died down too far, so as to maintain that differential where it belonged. Others had a backup widget which raised the pressure in the dry returns to keep the differential where it belonged if the fire got too enthusiastic.

    There is one interesting side effect of keeping that pressure differential in control: many systems did not have traps (some had static arrangements to keep any very low pressure stray steam where it belonged) or even vents -- they vented the dry returns directly to the atmosphere (sometimes into the chimney, to allow the chimney draught to help exhaust air from the system). Further, in the ones which did have traps -- like yours -- the radiator traps pretty much had nothing to do, and if they haven't been otherwise abused they would last forever (not so the crossover traps, but they were once and done when the system was fired up, and so they lasted pretty well forever, too).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    Yes, closing valves upstairs will cause a higher percentage of the total steam to go to the first floor and help with the mismatch. You will get tired of chasing around as conditions change trying to keep up with this though.

    In this respect the coal fired system was much better, as on a continuous basis the header pressure was so low (single digit inches of water) that the radiators were actually in slight vacuum always and therefore the ones in colder areas grabbing more of the steam and evening things out.

    Intermittently fired 2 pipe systems can easily take advantage of the balancing effect of vacuum however, delivering extra steam to the colder radiators automatically at the end of every cycle. If you never fill the system to a measurable pressure at any time (which is obviously never required) then valves can just stay wide open all the time.

    Intermittently fired systems running measurable pressure in the mains and chasing air out every cycle do not take advantage of this balancing benefit. When the burner stops on an open vented 2 pipe system steam flow to radiators stops instantly. The void being created by the collapsing steam in the radiators is filled by air from the vented dry return, rather than continuing the flow of steam from the mains. Through years of experience now I know for sure it is no small thing - and totally free for the taking simply by replacing the one vent on the dry return with a check valve.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Whatever...

    The trick with vapour systems is to keep the pressure differential within that narrow window. This can be difficult with oil burners, as the post purge/pre purge timing is such that the pressure may drop to nearly zero in that interval (the one vapour system I work and experiment with cuts out at 6 ounces, post pruge/pre purge and refire the pressure is down to 2 ounces; steam delivery never actually stops).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • neilc
    neilc Member Posts: 2,703
    edited November 2021
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    that 2nd to last picture,
    the gage up around 10, psi, not ounces,
    does that gage go back down to 0 when the boiler isn't firing and thermostat been satisified?
    cuz if the gage is working, then the Ptrol isn't, likely due to clogged pigtail,
    known to beat dead horses
  • PMJ
    PMJ Member Posts: 1,265
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    Whatever... The trick with vapour systems is to keep the pressure differential within that narrow window. This can be difficult with oil burners, as the post purge/pre purge timing is such that the pressure may drop to nearly zero in that interval (the one vapour system I work and experiment with cuts out at 6 ounces, post pruge/pre purge and refire the pressure is down to 2 ounces; steam delivery never actually stops).
    With all due respect continuous steam delivery at 2-6 ounces differential in my vapor system would roast me alive. My maximum differential is 2 inches of water and for only 5-10 minutes an hour during long calls. I believe @ChrisJ runs at a similar maximum number. The rest of the time with the burner off in vacuum it is more like 1 inch differential while the balancing is happening.

    There isn't any way that the pressure differential could have been double that with the original continuous coal fire either. The original Mouat documentation says 1/2 to 3 ounces - exactly what I show on the attached shot of my differential gage at the max I ever see. I have attached it for reference. It was designed as a continuously fired open vented system, but of course once fired up the air went out one time and that was it for air. I have found that keeping the system closed and air out between firings and allowing vacuum to form has dramatic balancing benefits.

    My piping and radiators are all the original 1926, and I know for a fact that the required steam flow that will partially fill radiators enough to heat on the coldest day will not ever produce a header pressure higher than 1-1/2 ounces with the dry return open to the atmosphere just like they said. It takes full radiators to raise the pressure higher than that, something that I have said time and again is never necessary with these systems and should be avoided for maximum efficiency and comfort. 

    As you can see in the documentation Mouat was able to use .5 - 3 ounces of pressure to modulate the damper. Such a thing is not practical with intermittent full fire. Truly even heat requires control measures beyond pressure and/or tstat in these systems.


    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • seandempsey
    seandempsey Member Posts: 28
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    Still absorbing all this, there are lots of terms I recognize but will need to read more of the recommended books and sources to fully take action. This is great though.

    @neilc That pressure gauge has never moved. I asked 2 different technicians who helped me about it, and both sorta just dismissed it. One tapped it and said it might be stuck, but both said it didn't really matter. I asked if it was the pressure of the steam system, and one said no and that 10psi would have blown up the whole system, and that it was for... something else. I can't remember what, but I was very clear that I had been reading the "We got steam heat" book and asked if my system was at 1 or 1.5psi, and the tech assured me this gauge was not measuring what the book was referring to.

    Having said that, I know a stuck, broken, or concerning gauge matters, I just don't have any idea what it is for, or what to do about it. Both techs didn't seem concerned and everything was working, I figured I'd get to it as I continue to renovate the house and all it's systems.

    While the boiler has a good service record, the homeowners for the last... well, maybe 90 years, weren't the typical homeowners. Since the 1930's it was a church-owned pastor dorm, and then after it was an elderly snowbird's house. Wear and tear is very low, but that also means things that easily should have worn out and been replaced decades ago are going strong. It also means the likelihood that the pigtail could be clogged is high, since there was no busybody homeowner like me constantly fretting over every detail.

    So if that's the case, what is my next step on that gauge? I've got kids, dogs, wife to keep warm for many years to come, so significant investment into the home's system is just fine, and finding Bangor's finest techs (or people who can drive here) is also fine if it's way beyond my abilities.
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Continuous steam delivery would roast me alive... well, yes. It would me, too. That's why there is a thermostat so the system only runs about every hour or so, just long enough to keep the house temperature correct.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • neilc
    neilc Member Posts: 2,703
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    So if that's the case, what is my next step on that gauge? I've got kids, dogs, wife to keep warm for many years to come, so significant investment into the home's system is just fine, and finding Bangor's finest techs (or people who can drive here) is also fine if it's way beyond my abilities.

    don't have either of those techs back in the house,
    https://heatinghelp.com/find-a-contractor/
    "one said no and that 10psi would have blown up the whole system",
    kinda correct, until he went further, don't have them back,
    it wouldn't have 'blown" as in danger, but would not properly function as mentioned by others,

    the gage is to measure the boiler pressure,
    you need a 0 - 30 to satisfy insurance and code,
    you need a 0 - 3 to monitor and know what your system, and Ptrol is doing,
    you could leave the broken one there, and add Tees under the Ptrol and mount gages there.
    known to beat dead horses
  • PMJ
    PMJ Member Posts: 1,265
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    Continuous steam delivery would roast me alive... well, yes. It would me, too. That's why there is a thermostat so the system only runs about every hour or so, just long enough to keep the house temperature correct.

    I read in your post that the boiler cuts out at 6 ounces and fires again at 2 ounces and "steam delivery never actually stops". I took that to mean continuous steam delivery with a differential header to dry return pressure always between 2 ounces and 6. What did I miss? As soon as you stop a boiler on a 2 pipe system steam flow into radiators stops instantly if the dry return is vented to the atmosphere. The dry return instantly becomes the highest pressure point in the entire system and it is air from that which fills the void being created by still condensing steam in the radiators, not any more steam from the mains.

    I'll say it again - allowing a residential steam system to fill radiators and hit header pressures above a couple inches of water at all is missing the point of these. The original designs intended that never to happen.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    PMJ said:

    Continuous steam delivery would roast me alive... well, yes. It would me, too. That's why there is a thermostat so the system only runs about every hour or so, just long enough to keep the house temperature correct.

    I read in your post that the boiler cuts out at 6 ounces and fires again at 2 ounces and "steam delivery never actually stops". I took that to mean continuous steam delivery with a differential header to dry return pressure always between 2 ounces and 6. What did I miss? As soon as you stop a boiler on a 2 pipe system steam flow into radiators stops instantly if the dry return is vented to the atmosphere. The dry return instantly becomes the highest pressure point in the entire system and it is air from that which fills the void being created by still condensing steam in the radiators, not any more steam from the mains.

    I'll say it again - allowing a residential steam system to fill radiators and hit header pressures above a couple inches of water at all is missing the point of these. The original designs intended that never to happen.
    You have forgotten about the residual high temperature heat in the cast iron of the boiler. This takes time -- not much time, but time -- to cool, and the boiling will not stop until it does. Nor will the main to dry return pressure differential drop to zero "instantly". Sorry.

    But you know all about these things far better than I, so I'll shut up.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    PMJ said:

    Continuous steam delivery would roast me alive... well, yes. It would me, too. That's why there is a thermostat so the system only runs about every hour or so, just long enough to keep the house temperature correct.

    I read in your post that the boiler cuts out at 6 ounces and fires again at 2 ounces and "steam delivery never actually stops". I took that to mean continuous steam delivery with a differential header to dry return pressure always between 2 ounces and 6. What did I miss? As soon as you stop a boiler on a 2 pipe system steam flow into radiators stops instantly if the dry return is vented to the atmosphere. The dry return instantly becomes the highest pressure point in the entire system and it is air from that which fills the void being created by still condensing steam in the radiators, not any more steam from the mains.

    I'll say it again - allowing a residential steam system to fill radiators and hit header pressures above a couple inches of water at all is missing the point of these. The original designs intended that never to happen.
    You have forgotten about the residual high temperature heat in the cast iron of the boiler. This takes time -- not much time, but time -- to cool, and the boiling will not stop until it does. Nor will the main to dry return pressure differential drop to zero "instantly". Sorry.

    But you know all about these things far better than I, so I'll shut up.
    Ok. I stand corrected. It is not "instant". But measured in seconds, not minutes. Air begins reentering the dry return in seconds after the boiler goes off. Why is that? The dry return was already at atmospheric pressure. It is because air is leaving the dry return starts going into the radiators right away. There is no where else for it to be going. Steam is also continuously condensing in the mains themselves. The reduction in volume happens very quickly and so air from the structure begins returning into the system quickly also.

    If you really want to see a boiler continue to boil for minutes after the flame goes out and steam continue to flow into the radiators with the boiler off, you have to close off the dry return and not allow the air back in. So no, I haven't forgotten at all about the residual heat in the boiler. What I have found out is that in vacuum dramatically more of that residual heat from the boiler and mains ends up in the rooms where you want it each and every cycle than open vented. It isn't close. It is precisely that heat which I deliver each and every cycle heavily favoring the colder rooms which evens things out.

    This bring us full circle and why I commented in this thread in the first place - balancing. @seandempsey ,
    in a two pipe system you can run around opening and closing valves and adjust heat for the conditions. That will in fact do a lot for today's conditions. Unfortunately tomorrow's conditions are different. I was startled by the dramatic effect natural vacuum between cycles has on balancing for conditions adjusting itself in real time. Desperately few have actually experienced this so most apparently don't believe it. It literally caused my upstairs/downstairs problem to go away and ended my fiddling with valves. If you are interested it is very easy to try in two pipe systems.


    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Quite correct on the seconds. The measured off cycle on Cedric is 30 seconds -- limited by the post pruge and pre purge.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    Quite correct on the seconds. The measured off cycle on Cedric is 30 seconds -- limited by the post pruge and pre purge.

    Ok I'm lost now. Please detail all the burn/off cycle times for Cedric for and average day in average conditions for 12 hours or something.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    On the rare occasions when Cedric cycles on pressure (coming out of a setback is almost the only time), he runs typically around 3 to 5 minutes on, 30 seconds off until the thermostat is satisfied. The thermostat cycles depend on the weather, of course, and can and do vary widely -- ranging from a 15 to 20 minute "kick" every few hours on warmer days (like today! 45 and sunny! -- might be an hour and half total run time today) to 30 to 45 minutes on and 15 minutes off on really cold windy days near design (say, -10 or so and 20 mph breeze... brrr....)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    Ok. Then not the seconds I was talking about.

    The seconds I was talking about is the time from when the burner goes off to when air begins entering the radiators from the dry return which gets that air from the atmosphere. Steam that is still collapsing in the radiator is replaced by more steam from the mains when the burner is running because the mains are at slightly higher pressure than the dry returns. When the burner goes off with an open vented return this relationship quickly inverts with the dry return being at higher pressure than the mains. This switch happens within a few seconds. However, if you close off the dry return and allow the entire system to sink into vacuum the mains remain at higher pressure than the dry return and steam continues to flow into them from the radiators. In this way the residual heat from the boiler and mains will continue to flow into the radiators for many minutes in a way which surely does not occur in an open vented system.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Really? I bow to your obviously far superior understanding of thermodynamics, fluid flow and physics. Don't pay any attention to me.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    Really? I bow to your obviously far superior understanding of thermodynamics, fluid flow and physics. Don't pay any attention to me.


    Cmon Jamie. Just talk about the specifics. Explain exactly where you think I have it wrong in this particular case if that is your position. Make your case.

    Trying to make this about who knows more about the entire engineering discipline of Thermodynamics and who should bow to whom helps no one. I don't think anyone should be bowing to anyone about anything. I limit my involvement here to only those things I have considerable personal experience with now. In this case upstairs/downstairs balancing in a two pipe system. That doesn't mean I think I can't be wrong about anything and I welcome questioning of my statements from anyone. If I have it wrong - show me!

    Somehow my pointing out that these systems were never intended to go anywhere near the pressures that vaporstats and pressuretrols operate on really seems to upset some folks here. I showed today that my system (Mouat) was designed for .5-3 ounces continuous. They designed in a boiler that running in the (adjustable) middle of its range would heat the place and installed enough radiation that at that amount of steam flow would never fill and exceed those pressures. There is a vaporstat on my big boiler. Probably came with the boiler when it replaced the coal one. When I moved in that big boiler was running straight until that vaporstat shut it off most every call for heat. Didn't take long for me to figure out that it was no use for decent control of my system. Why, because the original designers never intended the pressure to get that high!!! Letting the pressure get that high overfilled the radiators and made for really uneven heat!!! Hmmm.



    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Clearly you know that the original designers of vapour systems never intended them to get to -- well, let's say 4 ounces per square inch. With which understanding I beg to differ. However, I do not have access to the original design considerations which it would seem you do.

    I can only report what I have observed in several vapour steam systems -- not only Cedric -- which is that if the pressure is maintained at a steady value of around 4 ounces, and the radiators are correctly adjusted to account for radiator size and space characteristics, the heat output will be completely even. This, incidentally, is the pressure for which the coal fired draught regulators were adjusted, for what that's worth.

    I'm not really sure what "overfill" means, although perhaps it means that the radiator is hot all across. If the space overheats, that means that the radiator is larger than the space requires; it may have been (and can always be) controlled by partially closing the inlet valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265
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    Clearly you know that the original designers of vapour systems never intended them to get to -- well, let's say 4 ounces per square inch. With which understanding I beg to differ. However, I do not have access to the original design considerations which it would seem you do.

    I can only report what I have observed in several vapour steam systems -- not only Cedric -- which is that if the pressure is maintained at a steady value of around 4 ounces, and the radiators are correctly adjusted to account for radiator size and space characteristics, the heat output will be completely even. This, incidentally, is the pressure for which the coal fired draught regulators were adjusted, for what that's worth.

    I'm not really sure what "overfill" means, although perhaps it means that the radiator is hot all across. If the space overheats, that means that the radiator is larger than the space requires; it may have been (and can always be) controlled by partially closing the inlet valve.

    I copied the original Mouat literature in a previous post. The design pressure limits are in that.

    I am unable to get any header pressure above 2 inches of water until radiators fill enough that steam tries to go through the traps. That is what I mean by overfilled - a fill amount which is considerably more than the constant rate of steam required to heat the structure - more than the designers ever planned on with constant steam. So the point I am making is that anything over 3 ounces in my system is clearly more than is actually required at any time. 3-4 it really makes no difference - attempting to set cut in and cut out points inside a total range of 3-4 ounces makes no sense - especially if 2 max will heat the structure simply by more evenly spacing the firings using another simple method.

    Any fill amount beyond the required constant steam rate for the conditions necessarily requires a corresponding off time that goes below the required constant steam rate to end up with a total steam delivery that matches the required constant rate. Even heat is about minimizing this oscillation over and under. When you are doing really well at it the entire thing takes place inside the deadband of the tstat so it neither cuts out or cuts in. The longer the calls for heat are the more even the heat is by definition. Bottom line, if the tstat is being satisfied with one burn and that satisfaction happens while the burner is firing, the heat is no where near as even as it can be.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    I guess my system doesn't work, and it's all an illusion. But I've always had a good imagination. Over and out.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England