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Orifice Plates Install

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trivetman
trivetman Member Posts: 178
edited January 2019 in Strictly Steam
I've got a two pipe steam system with what seems to be a somewhat oversized (400K BTU - but it is a large house) boiler. There are no steam traps on the radiators. Based on some previous posts, it seems likely it was originally designed as an orifice system. All of the radiator valves look newer and it's a good bet there are no orifice plates in them.

When I first moved in a couple years ago, I saw it was short cycling on pressure. It looked like what was happening was steam was going through the radiators into the returns. When the steam reached the main vent on the dry return, that shut off and the pressure built. I've been trying to adjust all the valves to limit the amount of steam able to get into each radiator and have been somewhat successful. The distribution of heat throught the house is a lot more even now!

But it's not easy to do. There is a very very fine line between having the valve too open and letting too much steam in and closing it too much and having a cold radiator. So...are orifice plates available for purchase? I imagine it's easy enough to install them. Just take the valve off, insert plate and close it back up? I haven't been able to find them online. If I can get them, how do I size them? I've seen a number of widely conflicting sources about how to calculate EDR for radiators. Not sure what's right.

Thanks for the help. Love this forum.

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  • JUGHNE
    JUGHNE Member Posts: 11,062
    edited January 2019
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    I have done orifices on a small system such as yours and also on a large system, both with good results.
    First, I assume you have added a lot of main steam pipe air venting. And also venting for the dry returns.

    You must determine the average pressure the system will run at and still heat the house. You probably know this from adjusting the supply inlet valves and realize even the temp change will effect that operation.

    With the pressure determined you need the EDR of each radiator. I see from your chart you measured from the bottom of the rads….it is actually from the floor to the top of the rad.
    There are charts somewhere here to get the actual EDR of your rads.

    Typically you go for max of 80% of EDR for sizing.
    But depending upon factors you may want less.
    You can always drill the plates out if needed for more heat.
    Look for a posting about "I assume more than one trap is leaking steam", I posted my best guess of sizing.
    (If I were a younger person, I could pull it down and show it here :/ )

    I got the orifice plates thru Tunstall Corp, 413-594-8695 in Chicopee, MA. They directed me to a supplier I had to go thru.
    They might sell to you direct. I ordered all with a 1/8" pilot hole predrilled.

    This is the chart I used, sorry for the sideways shot and the notes.
    You find your EDR, multiply by .8 (or less!) and that determines the drill size for that orifice for that rad at that pressure. You can always increase the size, obviously start small. Some rads I used .5 EDR for sizing.

    I got this idea from Henry Gifford's article "How to Make a Two pipe steam heating really work" try to google that.
  • Ironman
    Ironman Member Posts: 7,376
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    Here's and EDR table:


    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • trivetman
    trivetman Member Posts: 178
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    Thanks both.

    I've read here that orifice systems are very sensitive to operating pressure, and looking at the sizing chart I understand why.

    Before I started adjusting valves to limit the steam flow, the pressure at the boiler was about 8 oz for a cycle of about 25 minutes before the vents closed up. Now it is somewhere between 12-14 oz as the radiators fill. I am wondering if I've closed off the valves a bit too much in response to steam leaking through as the pressure rises, which has just increased the operating pressure more. Should I revert back to the 8 oz pressure for sizing which the system was running at when everything was wide open?

    Second - I am wondering if it's foolish to try to do this operating without a vaporstat? I have a pressuretrol on the system now. It's set to the lowest setting (8 oz) but doesn't cut out until the pressure is about 2.5 lb. It seems the inevitable increase in pressure is just going to force too much steam past the orifice (or currently past the adjusted valve). Maybe putting a vaporstat in is the best first step.
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    edited January 2019
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    Yes -- go back to 8 ounces. It's a little less critical. And yes, sorry, you have to use a vapourstat set to cut out at 8 ounces and back in at say 3 or so. I'd do that first, and then start on the valves or orifices.

    And make sure your main venting is adequate -- if the boiler cuts out on pressure before the radiation is at least half full, it's not. Better yet, when you put the vapourstat on, put a 0 to 3 psi gauge on there too -- then you can really see what's happening. The pressure shouldn't rise to much over say 6 ounces until the radiation is really getting going.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • trivetman
    trivetman Member Posts: 178
    edited January 2019
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    Got it. Makes sense. Already have the 0-3 gauge.

    Thanks again
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    The residential job had a 571 EDR boiler with 662 EDR connected.
    There were no vents or traps on this system. No basis of what pressure would work.
    I used the 18 ounce column and 80% of each rad EDR.
    I figured I could increase the opening as needed, rather than be too large to start with.
    It now has a 0-16 oz vaporstat and operates maybe in the 8-12 oz range without serious short cycling.
    This was a 1921 house, still original windows etc. Only major upgrade was insulation added to the attic.
    I have not had to increase any orifice sizes......the radiation for the house is obviously oversized.
    662 EDR connected X 80% = 530 EDR connected. So now boiler is oversized a little......more than a little if orifices sized for 18 oz and running at 8-12 is taken into account.

    I don't get much observation time for the operation as this is 150 miles away and always trying to get on the road before dark and the deer come out.

    You could try without the vaporstat, it will talk to you if pressure gets too high.
  • trivetman
    trivetman Member Posts: 178
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    Seems like Vaporstat is the best first step. Might take me a bit before I get to it. Kids need some bookshelves built!
  • trivetman
    trivetman Member Posts: 178
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    Vaporstat time. I think this looks pretty easy but someone let me know if I am missing something.

    I've read on here that the pressuretrol can be put in series with the Vaporstat. Wiring seems simple enough after reading the manual. So, just take out my current pressuretrol, put a T on top of the pigtail with a couple elbows and nipples to space it out.

    Recommendations on what exactly to use for wiring? The wiring currently going to my pressuretrol is just hanging loose. Vaporstat's manual just says use 14 gauge moisture resistant. I'd rather not have to deal with conduit for the 2 inches between pressuretrol and vaporstat

    Here's the Vaporstat I am planning on using.

    Honeywell-L408J1009
    https://www.supplyhouse.com/Honeywell-L408J1009-Vaporstat-Controller-Steam-0-to-16-oz-in2

  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    I certainly wouldn't bother with conduit. On the other hand, I'm not all that keen on unarmored wire hanging loose like that, unless it is 24 volt wiring. If it's 24 volt, then... run what ya brung. Otherwise, I'd rewire with 14/2 BX. But that's just me...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ethicalpaul
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
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    Out of curiosity, can you still buy graduated radiator valves? This looks a lot like one of those old vapor systems that had special elbows. Like a Kriebel, Richardson, or Trane system (based on the shape of that 90 on the radiator).
    Never stop learning.
  • trivetman
    trivetman Member Posts: 178
    edited January 2019
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    Looks like it is 24 volt. The pressuretrol is supplied by this box which I assume is a transformer. I was wondering about the loose wires as well until doing a little research. Sounds like I can just run a couple of THHN lines between Vaporstat and pressuretrol without any worry.

    One more thing I am seeing...there isn’t enough room between the pigtail/pressuretrol and boiler to unscrew anything! Howd they get it on there in the first place?? I think I’ll probably have to cut through the pigtail to remove things unless anyone has a magic trick to share. Wont be hard to extend the nipple out once its off though.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
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    The magic trick is-use some unions to put it back together, with the new copper pigtail. Use enough wire so that you can rest the pressuretrol on the boiler while you are cleaning it in the future.
    A low pressure gauge (0-3 psi), on a tee would be a very useful addition as well.—NBC
    ethicalpaultrivetman
  • trivetman
    trivetman Member Posts: 178
    edited January 2019
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    Sounds like no magic to getting it off then. Dremel cut it is!

    Thanks for the tips. I do have a 0-3 gauge on already - on an extension out from where you see the 0-30 gauge. Protected with a ball valve
  • Chris_L
    Chris_L Member Posts: 336
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    Sounds like no magic to getting it off then. Dremel cut it is!

    No need to cut anything. Just turn the pressure setting down as low as it will go, and carefully remove the four screws from the bottom of the pressuretrol. (You need to take all the tension off of the adjustment spring or you'll never get the screws back in.)
    JUGHNE1Matthias
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    FWIW, some people have done that and ended up buying a new control.
    Most people in the business do not remove the 4 screws.

    IIWM, I would cut it just below the loop, remove the stub left in the 90, replace the 90 with a tee with cleanout plug. Nipple up add a union, add brass pigtail, add another tee, nipple up to control, nipple over out of tee and 90 to your gauge.

    The opening in the boiler sometimes gets plugged.
    The union lets you remove everything for cleaning.
    It is best to use brass or stainless steel fittings for all of this.
    With the control and gauge on the same P-tail then you know they are seeing the same conditions.
    It is common to leave the existing P-control in the circuit as a redundant safety control.
  • trivetman
    trivetman Member Posts: 178
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    > @JUGHNE said:
    > FWIW, some people have done that and ended up buying a new control.
    > Most people in the business do not remove the 4 screws.
    >
    > IIWM, I would cut it just below the loop, remove the stub left in the 90, replace the 90 with a tee with cleanout plug. Nipple up add a union, add brass pigtail, add another tee, nipple up to control, nipple over out of tee and 90 to your gauge.
    >
    > The opening in the boiler sometimes gets plugged.
    > The union lets you remove everything for cleaning.
    > It is best to use brass or stainless steel fittings for all of this.
    > With the control and gauge on the same P-tail then you know they are seeing the same conditions.
    > It is common to leave the existing P-control in the circuit as a redundant safety control.

    This was pretty much my plan. Glad u agree :smile: . I might wait until the cold is done this winter so any screwups dont create an emergency. Thanks.
    ethicalpaul
  • Fred
    Fred Member Posts: 8,542
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    There is a free floating pellet in that diaphragm that has to be perfectly centered if you take those four screws out. If that pellet rolls out onto the floor or under the boiler, you will be buying a new Pressuretrol. Cut the pigtail and buy a new Brass Pigtail and a couple nipples to raise it above the top of the boiler, with a union like has been suggested. My bet is that 1/4" nipple and elbow coming out of the boiler is also clogged.

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