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Parallel steam with dry return

Fizz
Fizz Member Posts: 532
essentially requires filling main and return with steam to maximize efficiency, yet, it seems a waste of steam. For instance, the current system we have is such, with a front main of 28', return of 26.5, back side main 31, return of 28. Both returns had Gorton #1's, and back side return filled quicker, yet both sides the rads are half heated before returns fill. Replaced front with G#2, with front return improvement, still both sides had rads heating well before steam gets to end of returns. It would seem that if filling return can be eliminated, then rads would heat more efficiently. Heatiing cycle runs 34-38 min. Improvement was not noticeable with G2. I'm wondering if putting vacuum vents on mains would reduce amount of air to be pushed-out of return so as to improve efficiency and reduce cycle time?

Comments

  • Danny Scully
    Danny Scully Member Posts: 1,319
    edited December 2018
    Where are the main vents? Ideally they would be at the beginning of the dry return, not the end.
  • Fred
    Fred Member Posts: 8,513
    @Fizz, As @Danny Scully said, if you can move the vents to somewhere right after the last Radiator Run-Out and plug the tapping where they are now, the steam will not have to push the air out of those returns and will start to be distributed to the radiators as the air in the returns can't go anywhere.
  • Fizz
    Fizz Member Posts: 532
    They're at the end of returns at boiler; the returns start about 6' from end of main on front return, and 3' on rear. Main and return have been insulated since pix.

  • Jamie Hall
    Jamie Hall Member Posts: 15,328
    As it so often is with steam, well... yes, maybe, sometimes, of course!

    One pipe systems -- yes, main vents at or very near the ends of all the steam mains, and sometimes on long runouts. If there is a dry return, it doesn't really need to be vented.

    Two pipe systems -- you may need vents at or very near the ends of all the steam mains -- but you may not. Whether you do or not depends on whether there are crossover traps into the dry returns. If you have crossover traps you not only don't need main vents at the end of the mains, you don't want them. However, all two pipe/dry return systems must have main vents on the dry returns, which are usually placed where they join and drop to the boiler (and yes, in two pipe dry return systems all the dry returns can and should join together before they drop, unlike one pipe systems)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Fizz
    Fizz Member Posts: 532
    Sorry, I meant vacuum on returns, as main have no vents, only radiator venting. If vacuum on returns would that reduce amount of air to be pushed-out?
  • gfrbrookline
    gfrbrookline Member Posts: 638
    Not sure as I have no experience with vacuum systems but Gorton #2's are only good for 20' of 2" main so you are still under vented by half if you factor in the returns. I would install a 90 degree elbow and add a Big Mouth plus your #2 and #1 on each, you have them and the more main venting capacity the better. This should cut your cycle run time down considerably.
  • Fizz
    Fizz Member Posts: 532
    Good advice! Thanks.
  • Fizz
    Fizz Member Posts: 532
    update: removed vent on front return to time how long it takes to get steam to open pipe; system heated the same with rads getting steam first, took 13 min for steam to get to open pipe area, but pipe drop to wet return heated and hardly any steam out of open pipe. Back side with vent in place took about 15 min for steam to get there.
  • Fred
    Fred Member Posts: 8,513
    Are you sure the bottom of the tapping that your vent is mounted into isn't clogged? Do you have your radiators vented so aggressively that they are the path of least resistance?
  • Fizz
    Fizz Member Posts: 532
    Yes; don't think so. Per Gerry Gill & Steve Pejak venting charts, pretty much in ball park. System runs at 1oz til last few min when it rises to 10-16oz. Rads as follows: Wall, 9SF, Gorton5, collumn, 30sf, MOM5; col,24sf, G5; iron tube, 21sf, MOM4. Front run: col,42sf, MOM5, col, 33sf,GD, tube,21sf, Heat timer min setting, col, 37.5 MOM6.
  • Jamie Hall
    Jamie Hall Member Posts: 15,328
    "System runs at 1oz til last few min when it rises to 10-16oz" and that is exactly where you want the vapourstat to shut off the burner.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Fizz
    Fizz Member Posts: 532
    Regretfully, don't have v-stat yet on this one, but the system runs bet 30-35 min before pressure rises.
  • Chris_L
    Chris_L Member Posts: 204
    Fizz said:

    Regretfully, don't have v-stat yet on this one, but the system runs bet 30-35 min before pressure rises.

    And this is perfectly normal. Once all the vents are closed, and the radiators full of steam, the pressure builds--fairly quickly if all the vents close around the same time.

    The v-stat is only going to save you the run time between whatever it is set at (e.g., 12 oz) and what the p-trol is set at (e.g., 2 psi) which might be just a minute or two.
  • Fizz
    Fizz Member Posts: 532
    Thanks Chris.
  • Chris_L
    Chris_L Member Posts: 204
    Fizz, you are welcome. I was looking for a plot I've done of the pressure in my system, but couldn't find one when I responded yesterday.

    Here is an example of what mine looks like from a cold start. I shut the boiler down at 7 inches of water, but you can see what I mean about the pressure rising quickly.


  • Jamie Hall
    Jamie Hall Member Posts: 15,328
    Lovely! I do like dataloggers... just don't have the need for one. The plateau region to which I sometimes refer shows up really clearly from 15 minutes out to about 27 minutes. The rise after that is dramatic -- but not unheard of by any means. What's really neat is that it appears that you system pulls a nice vacuum!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Fizz
    Fizz Member Posts: 532
    Very nice! Great data for referencing. Chris, what system do you have?
  • Chris_L
    Chris_L Member Posts: 204
    Thanks Jamie, Fizz.

    The pressure is collected with a home-grown system--an inexpensive pressure sensor hooked up to an internet-connected microcontroller (ESP8266).

    I first developed this to prevent excessive cycling of my tenant's oversized boiler, in their case shutting down the boiler completely for 14 minutes when the pressure reaches 11 inches of water. I also use one on my (less oversized) boiler to reduce cycling, and to email me warnings if the pressure goes too high, the LWCO activates, or the powerpile voltage goes too low (this is a millivolt system).

    The data logging is a side benefit done through a web service--ThingSpeak which receives pressure data every 15 seconds when the boiler is on and every two minutes thereafter.

    I made the plot in my earlier post using Excel with a data dump from ThingSpeak. Here is ThingSpeak's real-time plot for my tenants' boiler this morning--coming back from on overnight setback beginning at about 8:30:



  • Fizz
    Fizz Member Posts: 532
    Quite ingenious! Steamers could use more enlightenment and less demolition.
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