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Vacuum vs Regular 2 pipe System

What I’m wondering is do you end up with a over all (from a fuel cost standpoint) more efficient system by converting a working vacuum system over to a regular 2 pipe system by changing out the slow vacuum vents (like Hoffman 76 s) to non vacuum vents like Gorton #2 s ?

 

I can see the benefit of vacuum with a steady constant heat source (coal or a modulated burner) though with an ON /OFF burner system would think the slow capacity venting would diminish any benefits from derived from vacuum.



A while back Dave in QCA mentioned the possibility of using a trap for a main vent. I’m wondering if you could create large capacity vacuum main vent using a trap with a one way valve attached, sort of a “Super 76". That way you could get the combined benefit of both fast venting and vacuum.  Thoughts?



I keep day dreaming about Gerry Gill’s marvelous mini tube system and how it would run on a really deep vacuum.

- Rod

 

Comments

  • Enreynolds
    Enreynolds Member Posts: 119
    I am using Anvers Vacuum Check valves

    On the new mini tube system I  am installing in my house, I have used these valves.

    http://www.anver.com/document/vacuum%20components/vacuum%20valves/check-valves/CV114F114F!.htm

    Notice the low cracking pressure.
  • Dave in QCA
    Dave in QCA Member Posts: 1,764
    Not much to vent

    Hi Rod, I don't know what the real world benefits are from running in vacuum.  The current common practice and theory that vacuum is ONLY for coal seems to come from steam guides published by Hoffman Specialty.  However, in reading and studying all of the Dunham materials that I can get my hands on, they were saying at the time the vapor and vacuum systems were being installed, that they were good on all types of firing especially gas and oil because it would tend to smooth out the on/off characteristics of those systems.  How does it work in real practice, I don't know.  But, there have been several good reports from other wallies that the results are quite good.  I hope to find out this winter and will report my observations.



    Regarding vent capacities, remember that since you are preventing air from returning to the system, that in subsequent cycles there is not much, if any air to be vented.  So, it would seem that the capacity of the vent would have an effect on the first cycle, that on subsequent cycles that effect would be much less.



    Also, I have observed that while the Gorton 2 has a very high capacity on a cold start, its effectiveness is greatly reduced on subsequent cycles, even if limited to 1 cycle per hour.  My basement stays warm, probably 80 degrees near the ceiling where the vents are located.  All of the steam pipes are insulated and when the system fills with air following a steam cycle, the air is all heated to the temperature of the main.  By the end of the cycle, the mains will drop to about 135 degrees, which is well within the range where the Gorton will begin to close.  So, on my system, while the Gortons are real fast on a cold start, they do not perform well at all on subsequent cycles.



    In redoing my system, I will be replacing all main vents with crossover traps as it would have been originally.  There will be one point of venting located on the return piping. Since all of the traps are in good working order and the possibility of water backing up into the return system is eliminated by a vaporstat, I could simply vent the system with an open pipe. I have considered installing a simple swing check valve to allow it to draw a vacuum.  Not sure how tight a standard check valve would be.  EnReynolds vacuum check recommendation is also a great idea.  Another option I have considered is to simply vent through a Hoffman 76.  The steam closing and float function of the vent would be a safety backup for a failed trap.  The built in check would be my primary reason for choosing it.  But, the venting capacity is slow.  Does it have an impact on cycles after the initial cycle where the air is driven out?  That is still an unanswered question. 



    If it works the way Dunham and all of the other Vapor/Vacuum proponents described, steam circulation will start very shortly after firing is started.  Vapor circulation is quite rapid and depending on the amount of vacuum, the vapor will be flowing at temperatures well below 212, thus providing a moderating effect on the system.  If the boiler continues to fire, the temperature of the boiler water and the vapor will rise and the level of vacuum will diminish.



    Advantages....

    Reduced temperature in the mains and system piping, thus less piping losses.

    Improved steam circulation - little or nor air to be venting once vacuum is established.

    Reduced corrosion because soluble gasses are kept out of the system.

    Reduced temperature of the radiators, leading to a more level temperature in the conditioned space.  Less overheating of the space means less wasted fuel.



    Anyway, that is what the vapor-vacuum committee of the Dead Men's club claimed.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • vaporvac
    vaporvac Member Posts: 1,520
    BoilingPoint in Vacuum

    Implicit in the reduced temps of the piping and radiators is the lower temperature required to boil water in a vacuum. I recall that at 20" of vacuum the water boils at @160degrees. (That could be wrong:)) I suspect that's where much of the savings will come from, or at least I'm hoping so.

    My own Trane VV system was originally installed for gas so your research with Dunham helps justify my thought that it wasn't only for coal.  However, I can see where coal's long slow heating cycles with  gradual cool-downs would work well with the VV system.  A modulating burner with outdoor reset would probably help simulate these circumstances. I often wonder how my original gas boiler actually worked.

    I'm very excited to see how this does work out in "real life".
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Dave in QCA
    Dave in QCA Member Posts: 1,764
    Looking forward to it

    I will look forward to hearing how your system works out for you.  Are you getting close to a replacment project?
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Rod
    Rod Posts: 2,067
    Vacuum

    Thanks to everyone for their replies.  Dave- I always read your input with great interest.  On the Gorton #2 s - It didn’t really attract my attention until I ran across a comment by Gerry Gill that mentioned the Gorton #2  closing at about 145 deg. F  After that I watched the Gortons more closely and have noticed the same thing you did  as to slowing of venting in subsequence cycles after a cold start. Due to the higher venting capacity / economic benefits of the Gorton , I initially dismissed the Hoffman 75/76 but now see it may be an advantage to include a Hoffman in an “antler” of multiple Gortons or even to go completely to the Hoffmans.  While there  definitely would seem to be an advantage to do so, how much you actually would gain I don’t really have a handle on.



    What level of vacuum do you hope to achieve?  From my experience with using vacuum in plastics manufacturing,  I’ve learned that trying to find small vacuum leaks is much harder (almost impossible) compared to finding (pressure) air leaks, so I’m rather skeptical of  how tight you can make these antique steam systems.  Does Weil McLain (with soft gaskets between their boiler sections)  have any comments about using their boiler under vacuum?  From just a design stand point this area would favor push nipples.

     

    Eric - As the mini tube system needs a pumped condensate receiver, how are you handling the vacuum with this.   A lot of us are very interested in what you are doing so please keep us updated.



    Colleen- Attached is a table of vacuum/pressure /temperature with boiling points that may be of use to you.  I’m wondering if pulling 20 inches of mercury might be a little overly optimistic target.  It’s fairly easy to pull 5 HG but it gets harder after that.  Without using a vacuum pump, 7 to 10 HG might be in range though it would definitely depend on how tight you can get your system.



    There was an interesting thought sometime back on using a shop vac to help with the initial  evacuation of air from the system.   A good shop vac generally will pull at least  200 mbar of vacuum which is close to 6 HG (5.92).   The shop vac’s high volume of air movement  would remove the air in the system very quickly, at 6HG, the boiler water would produce steam at a little over 200 Deg  F and the steam would quickly be distributed.

    - Rod

     
  • vaporvac
    vaporvac Member Posts: 1,520
    Inches of VAc

    Thanks for posting that...I was only 1deg off!  I am SURE I'm being overly optimistic. I just used that as an example, mainly because my vaporstat goes down to 20 inches of vacuum.  I can dream, can't I? Maybe when the time comes we can try to figure out how to find  leaks.  Colleen
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Enreynolds
    Enreynolds Member Posts: 119
    Rod

    The only reason a minitube system needs a condensate pump is lack of B dimension.  I have been running (testing) my system with a cut out of 1.5 lb. and have had no issues.  If I need to run higher pressure, I have plans for a pump trap, but I hope to not have to go there. The system has been running great, and the only time it pressures out is when I force it to run past call for heat, or if I turn off several of the baseboards.  I should be able to counteract this by dropping to low fire, once I get the fabrication done to implement that on the Carlin EZ-Gas.  You are correct about the difficulty of finding vacuum leaks:  I have found 3 of my take offs have leaks that only show up when I pressurize the system to > 5 lbs.  Currently I am drawing down to about 0.3 psi of vacuum simply by condensing the steam in the system.  I hope to do better than that.

    I have heard one thing that I never thought I would hear from my wife though: "Can we please turn down the heat?"  Marked that on my calendar.

    Eric
  • Rod
    Rod Posts: 2,067
    Vacuum

    Hi Colleen -  As a 20 inch HG vacuum is the equivalent of a negative 10 PSI, I'm just a bit skeptical whether it can/could be obtained with these old antique systems. Theoretically being able to produce steam over a wide temperature range really fascinates me however I've come to the conclusion that the better use of vacuum is to distribute steam rather than hoping for wider temperature range steam production.Therefore just a few inches of HG should do the trick. If it works out that the system is tight and is able operate at higher vacuum, that's a bonus. I just think you have to be cautious about not dump a lot of time, effort and cost on pursuing higher vacuum levels which may be a pipe dream. 

        Vacuum leaks can be really hard to find. The best way is to use an ultra sonic detector. We used to use them a lot to check for leaks when we were vacuum bagging composites. The downside of this is that they cost in the neighborhood of $300+ for a half way decent one.

    - Rod
  • Rod
    Rod Posts: 2,067
    Mini Tube System

    Hi Eric- If I remember it correctly, Gerry Gill mentioned that his system runs at around 5 PSI which was needed to overcome the greater friction loss of the mini tubes.  The resulting high A/B Dimension created a need for a  condensate tank.  What differences are there between yours and Gerry's systems?   What size tubing are you running to and from your heat emitters and what are you using for venting?  I've been trying to talk my cousin into putting a mini tube system in his new home. I think they have a lot of potential.  An ideal system would be to combine a mini tube with JAGA type DBE radiators.  http://www.jaga.co.uk/technology/dbe

    - Rod
  • Enreynolds
    Enreynolds Member Posts: 119
    Gerry's system

    I was looking back at that thread today.  I think that you will find that Gerry has set his cut out at 2 PSI and that hecause e normally sits at 1.5 PSI after all the traps close.  He did mention that some mini-tube systems run at as high as 4 or 5 PSI.



    My house was built in 1926, a two story balloon framed colonial.  It originally had a gravity hot air (octopus) furnace, which I think started out burning coal.  It was converted to Fuel oil somewhere  along the line.  The price of fuel, the inefficiency of the system, and the cold spots all through the house convinced us we had put off the heating replacement long enough.  We considered hot water and forced air, but both required substantial demolition, and my wife has dust allergies, thus no forced air.  Gerry posted his mini-tube system and I had found my solution.

    Because of the balloon framing, it was (fairly) easy to pull pipe through the exterior walls from the basement to the second floor.  The only damage that I did to the walls was behind the existing baseboards, in order to drill through the wall plate into the basement.  I used 3/8" refrigeration tubing for both the supply and returns, connected to Governale cast iron (I know) baseboard.  There is a North (131 EDR) and a South {122 EDR) Main branch, with plans for another 30 EDR in the attic in the future.  The mains are 1" copper, and the returns are 3/4" copper.  I have installed a Burnham Megasteam 288 with a 4" drop header for some dry steam

    Firing this set-up is a Carlin EZ-Gas burner modified to accept custom Orifice plates for ease of interchangeability.  The gas train starts off with a dedicated 3/4" line feeding the stock Carlin gas valve, through a Brasscraft 3/4" ID flex line, into a Honeywell V5055B gas valve, controlled by a Honeywell  V4062 1008 Hi-Lo-off controller, then into the orifice union on the Carlin.

    As for controls, I am using a Honeywell L6081053 0-4 psi Hg Vaporstat, as the boiler controller, and a Honeywell L408J1009 0-16 oz. Hg Vaporstat for the Hi-Lo control.

    I will post some before after pictures, once I get the basement cleaned back enough for the work to be recognizable.

    I am enjoying the experiment, and my wife is happy to boot.  It doesn't get much better than that.
  • ttekushan_3
    ttekushan_3 Member Posts: 939
    8 or 9 lbs was required for SelecTemp systems

    The original minitube steam system was the SelecTemp by Iron Fireman. The pressures were around 8 or 9 lbs because the steam was the power source for the turbine-driven blowers in the SelecTemp unit heaters.



    If you don't have those heaters, surprisingly low pressures will do the job despite the vanishingly small minitube supply lines.
    terry
  • twopipe
    twopipe Member Posts: 16
    Vacuum

    When I moved into my house, I found that someone had replaced the old check valve on my vapor vacuum system with a Gorton #2- just like you were considering. Once I got to understand how the system was originally designed (1910 Webster two-pipe system) I decided to restore the check valve. The system (after some leak repairs) can pull 15-20" of water of vacuum- for a while. Its not perfectly tight and it never will be, But there is no need for a large vent- once it gets going there is very little air in the system to vent from cycle to cycle, The heat is even, and since the water in the boiler keeps boiling for a while after it stops firing and it goes to vacuum, I believe that it is somewhat more efficient.
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