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Pigtail - installation question



I’m replacing the gauges on the Weil McLain LGB-9 steam boiler in my 1920’s coop building, and I think that one gauge was originally installed incorrectly. Btw, I’ve set the pressure to about 0.6 psi with a 4oz subtractive differential, and it runs amazingly well at this low pressure. Fun fact, when I took over the boiler operation, it was running at a whopping 7.0 psi! Anyway, check out the photos I’ve attached if you’d like to help with my question. 

It seems to me that the pipe from the water cutoff float which leads up, then back, then down and then out left and right acts as a de facto pigtail to protect the pressure controls and the large 30 psi gauge. The pipes leading up to those gauges from the horizontal piece do not get as hot as steam to the touch, but the pipe leading up from the water cutoff float does. However, the smaller gauge in front does not seem to have that pigtail protection, right? So I have two questions for you kind folks who know this stuff:

1) If I’m replacing the low-pressure gauge currently in front, I should find a different place for it, like extending the horizontal pipe which the 30 psi gauge is on, and then up from there, right? The gauge I was planning to use is here: https://www.supplyhouse.com/Winters-Instruments-PLP301-2-1-2-PLP-Steel-Low-Pressure-Gauge-1-4-Bottom-NPT-w-Brass-Internals-0-32WC

2) If I replace the 30 psi gauge with a “Tridicator” gauge which measures both pressure and temp, like this one: https://www.supplyhouse.com/Watts-0121663-LFDPTG-1-3-Bottom-Entry-Pressure-Temperature-Gauge-0-50-psi
then I would need to install it without this pigtail protection for the temp gauge to read properly, right? So it would be better off in the position where the smaller gauge is currently, unprotected by the de facto pigtail. Btw, the only reason I want the tridicator is for my own edification about the boiler’s internal temp, and for code compliance, I need a pressure gauge that is at least 30psi. 

Thank you for your time answering this noob’s question. 

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    That setup is fine as is --the way the piping is arranged provides a water seal, which is what a pigtail would do. You don't need another pigtail on anything.

    Why would you want a tridicator? Are you also using this boiler as a hot water heating source? If not --nif it's all steam heat --there's no point to it. You know what the temperature is -- water boils at your pressures at right around 212 F.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    Well the one gauge isn't behind the water trap Jamie :)

    I agree the tri unit won't be very helpful, especially distanced from the boiler
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • GBC_illinois
    GBC_illinois Member Posts: 104
    edited February 2022
    The tridicator is not to verify that it will top out at 212 when producing steam, it's to see how quickly the boiler heats to 212 from the off cycle, and is only for my own nerdy interest.

    I'm going to replace both gauges anyway since the lower pressure gauge is blown from a previous high-pressure event before I lowered the cutoff pressure to 0.6psi. But it sounds like what you are saying is that the original low-pressure gauge installation placement was fine, and would not blow the gauge with temps in excess of its limit?
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    edited February 2022
    I did put a pressure/temp gauge (normally used in a hot water "boiler") in my steam boiler under the water line so I could also see the water temperature, for exactly the reasons you described. I just don't think it would work above the water line.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
    GBC_illinois
  • GBC_illinois
    GBC_illinois Member Posts: 104

    I did put a pressure/temp gauge (normally used in a hot water "boiler") in my steam boiler under the water line so I could also see the water temperature, for exactly the reasons you described. I just don't think it would work above the water line.

    I see what you mean, I think -- if a temp gauge is above the water line, then it won't detect any water or water vapor until steam temp is reached, and won't have anything to measure the water temp. But then if its below the water line, will it accurately measure pressure too?
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    edited February 2022
    You don't need it to measure pressure. You are measuring pressure up there on your control structure. But yes, it will measure pressure, but hopefully your system's pressure is way below what will register on that gauge
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • GBC_illinois
    GBC_illinois Member Posts: 104

    You don't need it to measure pressure. You are measuring pressure up there on your control structure. But yes, it will measure pressure, but hopefully your system's pressure is way below what will register on that gauge

    The reason I want the tridicator to accurately measure pressure, if possible, is because I plan to replace the current 30psi gauge, which as I understand is required by code. I'm afraid I will fail the next inspection if they determine that my 30+psi gauge is improperly installed to detect a high pressure situation.
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    Right but yeah if you are worried about inspection, I would put a 30psi gauge up on your control tree. They may not like it below the waterline because...inspectors

    But the tridicator is not going to be accurately measuring your hopefully low pressures. It has a 0-50psi range
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • GBC_illinois
    GBC_illinois Member Posts: 104

    Right but yeah if you are worried about inspection, I would put a 30psi gauge up on your control tree. They may not like it below the waterline because...inspectors

    But the tridicator is not going to be accurately measuring your hopefully low pressures. It has a 0-50psi range

    That is why I want the second gauge. The 0-50psi pressure reading from the tridicator would be ONLY to satisfy the inspectors. The low pressure gauge (which is 0-19oz/in) is what I would use for my readings. But it sounds like I need to measure the water temp separately if I want to measure it at all, below the water line, rather than having the tridicator above the water line.
  • GBC_illinois
    GBC_illinois Member Posts: 104
    edited February 2022
    tommay said:

    What's the idea of the three watchers?
    Ep, right...no correct water trap or to big of one. Water will build up in that horizontal up to the tee behind the small gauge, which as you say, isn't behind the trap, which is probably why it failed... saturated, having no where/way to return to an appropriate level/volume.

    RE: Three watchers (I assume you mean gauges, sorry if I'm dense):

    1) One 30+psi pressure gauge required by inspectors, but useless to me for reading a low-pressure boiler running at 0.6psi.
    2) One low pressure gauge 0-19 oz/in of pressure for maximum accuracy in my own readings
    3) Temp gauge only because I'm a nerd and I feel like it, mostly to read how fast the water in the boiler comes up to temperature after turning on.
    wmgeorge
  • GBC_illinois
    GBC_illinois Member Posts: 104
    edited February 2022
    So, it sounds like my best bet is to:
    • Keep the old 30psi gauge where it is, and don't attempt to replace it with a tridicator, which is not designed to measure sub-boiling temps in a steam boiler above the water line
    • Put the new low-pressure gauge behind the control tree, so that it is protected from the steam temps, probably adding a new segment to the tree to do so.
    • If I want to measure temperature for my own nerdy ambitions, get a third, Temp-only gauge for this, and put it below the water line somewhere
    Sound right?
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    That sounds right to me
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
    GBC_illinois
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    @Fdarby82

    Everything You have is fine except for one thing:

    Replace the low pressure gauge and leave it in the same location put a pigtail under it and put a 1/4" ball valve or gauge cock under it. Leave it shut off unless you want to check the pressure open it and close it when you are done.


    Making the seal-the pig tails is ok for the controls and the 0-30 gauge but the head of water will affect the reading on the low pressure gauge. Keep it where it is
    GBC_illinois
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,005
    Second vote on the isolation valve for the low pressure gauge. Only have it reading pressure when you want to know the pressure.

    Structurally they may not be able to withstand any pressure excursions and could distort, leak or worse. Some gauges are only structurally capable at 130% of the full scale range. The other choice, mentioned in other discussions, is a Magnehelic that can withstand the 30 psig.

  • SteamBoiler
    SteamBoiler Member Posts: 90
    Fdarby82 said:

    I’m replacing the gauges on the Weil McLain LGB-9 steam boiler in my 1920’s coop building, and I think that one gauge was originally installed incorrectly. Btw, I’ve set the pressure to about 0.6 psi with a 4oz subtractive differential, and it runs amazingly well at this low pressure. Fun fact, when I took over the boiler operation, it was running at a whopping 7.0 psi!

    Massively unrelated question, I am a relative newbie as well to steam. What exactly did you do to enable the heat to run at this low pressure? Replace vents and traps? My system is cut-in at 0.5psi and cuts out at 2psi (1.5psi differential add-in) and I needed it all for a 35 minute heat call recovering from 65F to 67F at 6am, 10F outside, a couple days back.
  • jhewings
    jhewings Member Posts: 139
    @SteamBoiler This question requires some information about your system. I suggest you start a new thread and describe your system (1-pipe or 2-pipe for starters) and post pictures of your boiler and near boiler piping, main vents, and a typical radiator. I suggest you purchase "The Lost Art of Steam Heating" and /or some of the other books by Dan Holohan.
  • GBC_illinois
    GBC_illinois Member Posts: 104
    edited February 2022
    I’m replacing the gauges on the Weil McLain LGB-9 steam boiler in my 1920’s coop building, and I think that one gauge was originally installed incorrectly. Btw, I’ve set the pressure to about 0.6 psi with a 4oz subtractive differential, and it runs amazingly well at this low pressure. Fun fact, when I took over the boiler operation, it was running at a whopping 7.0 psi!
    Massively unrelated question, I am a relative newbie as well to steam. What exactly did you do to enable the heat to run at this low pressure? Replace vents and traps? My system is cut-in at 0.5psi and cuts out at 2psi (1.5psi differential add-in) and I needed it all for a 35 minute heat call recovering from 65F to 67F at 6am, 10F outside, a couple days back.
    In my non-expert opinion, I think the piping and radiator system you have determines the minimum steam pressure required to work, and increasing that pressure over what is required will not make a difference to your heat output. When we reduced our steam pressure from 7.0 psi to 0.6 psi max, there was no reduction in heat produced by the radiators; it was simply set unnecessarily high previously to no benefit. As long as steam is able to reach the rads, they should heat up to something around 220 degrees F (this will change a few degrees at high pressures, but not enough to make a real difference in the heat output).