The Wall
Forum / Strictly Steam / Venting risers after the supply valve?
  • Post a Reply to this Thread

    Venting risers after the supply valve? (13 Posts)

  • Jim_from_Worcester Jim_from_Worcester @ 11:10 PM
    Contact this user

    Venting risers after the supply valve?

    I have a question regarding venting of my one-pipe steam system. I intend to vent my mains, and max venting would require 4 Gorton #2’s on one end and 3 on another. However, some of the risers are of considerable length from the mains and two even rival the short main in terms of volume (3ft^3+) and are 2-4 times the volume of the other risers. Having looked up some information from previous Wall posts and armed with Dan’s recommendation for venting oversized radiators, I thought it worth to ask if anyone has ever used the tappings on the radiators closest to the supply valve to aggressively vent the risers, as opposed to venting them before the valve, and a normal (say, Hoffman #6) vent in the typical far position to heat more slowly from that point. I figure this way I will have a better chance of balancing the system without all the hassle of tapping the risers.

    The system is of modest size (267ft^2 EDR, radiators only, and 64 MBH), but has clearly been tinkered with (some of the radiators do not appear to be original). I have not performed a manual j for the house yet—I’m just getting my feet wet in that regard—to see if the system is sized properly. If my calculations are correct, the boiler (WM SGO-3) seems to be 34% oversized (358 ft^2 steam/86 MBH), but does provide DHW.

    As a note, I still have the old asbestos on the piping (none on the near boiler) and plan to have it removed this summer and reinsulate. There appears to be a ¾” tapping at the end of the short main, but I can’t seem to locate one on the other main (I am hoping for a pleasant surprise when the asbestos is gone). So, in short, I won’t be experimenting with the vents until the fall, most likely. I was also wondering if anyone has had luck with balancing a system with the Macon or Danfoss TRV’s—seems like overkill for the $ but I figured I’d ask, especially if it could prevent buying additional vents for the radiators.

    Thanks!
  • nicholas bonham-carter nicholas bonham-carter @ 11:53 PM
    Contact this user

    Main venting question

    If you can find a tapping at the end of the dry return (assuming it is a parallel flow system), then the main vents would be best there, close to the boiler where you can see their action.
    These generous main vents work best at making all the radiators get heat simultaneously when the radiator vents are slower, causing the mains to empty of air, and fill with steam first before any riser has filled. A good low-pressure gauge will tell you when you have enough main venting, or you can calculate the volume of the pipes plus the volume of the boiler steam chest plus a fudge factor. The gauge is easier, as it will show the resistance of the venting to the air escaping, which is the key. 2 ounces is the ideal back-pressure during the venting phase, to prevent the gas company from making too much money from you.
    Any insulation which is removed should be replaced with fiberglass, so you may wish to keep the asbestos insulation, and cover it. Insulation is very important to get the steam into the radiators without loss of heat from bare pipes.--NBC
  • Dave in QCA Dave in QCA @ 9:28 AM
    Contact this user

    Step by Step

    I'm in complete agreement with NBC.  Address your main venting first.  Keep your main vents on the mains, not the radiators.  If you remove old insulation make sure you replace it with new.  If you do not have connections for vent, you can have a welder come out an install a "thread-o-let" on your main.  It is probably the easiest and cheapest option.

    Remember, vent your mains fast and your radiators slow, very slow.   Once you have completed all of the above you can see if you still have any balance problems.  If you do, then you could proceed to venting that riser and/or increasing the venting on the slow radiator.
    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
  • Jim_from_Worcester Jim_from_Worcester @ 10:01 AM
    Contact this user

    My system

    Is a counterflow arrangement. I do plan to vent the mains and insulate, no question there. I have tried to balance the system using the existing adjustable vents which I boiled in vinegar for about half an hour. I calculated the piping volume (but not the steam chest--I will add that in!) and set the vents according to a matrix for supply volume. The system was much improved after that, but there is still quite a bit of lag time between the first and last radiator starting to heat. I have adjusted the vents accordingly, but have not been able to improve things much since the initial changes.

    Before I spring for new vents I wanted to explore these other options, however (venting risers and TRVs), especially now that I have the summer to tinker with it. I have seen many folks on this forum who have vented their risers on a counterflow system by adding vents before the radiator supply valve. I don't really want to do that. My question was whether I could get decent results--if needed--by venting the individual risers using the near-valve tapping on the radiator. It seems to me that the air would favor an aggressive vent close to the valve, and that is where the steam would arrive first, shutting that vent, which would allow the rest of the radiator to vent slowly through the far, normally sized vent.

    It also seems to me that if that is the case then folks on this site would have already tried it--which makes me think I missing something, and I think that something may be this: when the steam enters the radiator with two valves it will push all the air out of the bigger vent first, regardless of where it is on the radiator, defeating its purpose of venting the risers only. I'm trying, like Dan says,  to think like steam, but I kind of lose my way here.

    Thanks!
  • Dave in QCA Dave in QCA @ 10:12 AM
    Contact this user

    Last Resort

    I think you will likely see great improvement when you at venting to your mains. 

    However, in direct answer to your question, I do believe that I have seen a few threads where folks have done exactly what you're proposing and that it was successful.
    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
  • Jim_from_Worcester Jim_from_Worcester @ 11:10 AM
    Contact this user

    Thanks Dave

    That is good to know if I still have some issues after the main vents go in.
  • MarkS MarkS @ 11:16 AM
    Contact this user

    Venting worksheet

    Forum member jpf321 put together a spreadsheet to calculate venting requirements and make recommendations for Gorton and Hoffmann vents.

    You can get Excel and OpenOffice versions of the worksheet here: http://www.ypgmedia.com/heatinghelp

    It doesn't have a selection for risers, but you can just select "Main" in the "RadType" column and set the pipe size to the diameter of your risers.
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
  • Jim_from_Worcester Jim_from_Worcester @ 12:04 PM
    Contact this user

    Thanks Mark

    I will check this out. Been reading your posts about the Midco--great stuff. I am looking at a conversion with a Riello 40-G120. Do you have any suggestions of what I should be looking for? Per my plumber neighbor I am assuming I will need an indirect HW tank, but not sure what I should get--metal flue liner as well?
  • MarkS MarkS @ 1:05 PM
    Contact this user

    DHW

    Hi Jim, I assume you're converting from oil to gas. Don't know the codes in your area but you'll most likely need a metal chimney liner. Even if it's not required by code it's still a good idea.

    Do you have gas service already? Make sure you account for the btu requirements of all your gas appliances. I had to have a larger capacity gas meter installed, and we'll be running a larger service line into the house to accommodate the Midco burner.

    How do you heat your domestic hot water now? Tankless coil? Icesailor shared an interesting and inexpensive indirect solution that he's been installing for years. It's the fourth post down in this thread: http://www.heatinghelp.com/forum-thread/141007/Tankless-coil-into-water-heater-tank.

    At my house it's just my wife and I, so a couple of years ago I put in a "scheduled hot water" system using an old setback thermostat I had around, a flow switch, and a time-delay relay hooked up to the aquastat on the tankless coil. It's relatively cheap, and it cuts my non-heating season fuel usage by 50% or more versus aquastat-only control. The downside is that if you want hot water during a scheduled "off" period, you need to wait a few minutes for the boiler to heat up. If you're interested, send me a PM and I can give you some more details.
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
  • Jim_from_Worcester Jim_from_Worcester @ 2:17 PM
    Contact this user

    DHW

    Is supplied by a tankless coil--5 gpm. It already struggles to keep up with demand at times (laundry, dishes and bath time are not a favorable combination). We have two youngun's and often either my wife or mother-in-law are home during the day, but even so, I love the idea of the "scheduled setback." Not sure it's best option considering our situation.

    My dream is put a one room addition on the rear of the house with solar HW, but I figure a small storage tank now to keep pace with demand could be scaled up later with a larger tank and heat exchanger. I will certainly take a look at Icesailor's post.

    It is an oil to gas conversion. There is old supply line which is unused and I'm expecting will need to be replaced (I think the house was originally built with a small gas furnace and then converted sometime in the 1920's or 30's). I expected the need for the metal flue liner. We will likely install a gas range once we have a new supply line in.

    Thanks for all the info.
  • Charlie from wmass Charlie from wmass @ 10:07 PM
    Contact this user

    The gas line was probably

    used for cooking and maybe hot water when the boiler was coal fired. If it comes in the basement wall it will need replaced.
    Cost is what you spend , value is what you get.
    cell # 413-841-6726
  • nicholas bonham-carter nicholas bonham-carter @ 6:59 AM
    Contact this user

    Counter flow measures

    You could try putting a manifold on the last radiator of 2 gorton d's, with all the other rads vented slowly with Hoffman 40's.
    Remember that you are balancing the system by having an equal resistance to the escaping air (back-pressure) on each rad, except for the last one which is now the main vent. This is where the 0-3 psi gauge comes into it's own by showing you that back-pressure (2 ounces)..--NBC
  • Jim_from_Worcester Jim_from_Worcester @ 9:06 AM
    Contact this user

    Thanks Nicholas,

    I will see where I end up when I put the main vents in.

    Jim
  •  
Post a Reply to this Thread