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Need Help with Boiler Pressure

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Minnesota4114
Minnesota4114 Member Posts: 10
edited November 2023 in Radiant Heating
My top floor radiators haven’t been getting hot and no water came out when I bled them. So, I did my best to look into what to do and it seems like this may be a pressure problem. My gauge currently reads 10 PSI. Seems like it may need to go a bit higher. But I’m not sure how to get it there. I’m not sure where the water feed valve is. This is an old Sears boiler. It’s connected to an expansion tank that is in a bedroom close by. I did my best to take pictures. I’ll post them with this, but let me know if you need anymore to help. Thank you!

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  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    Can you get some photos from a bit farther back? I can't really make out how the various pipes I see are connected to your domestic water and to the boiler.

    That said, it is quite possible that your pressure is too low -- 10 psi is only enough to make 23 feet, and the actual pressure may be less.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114ethicalpaul
  • hot_rod
    hot_rod Member Posts: 22,479
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    Maybe go out a but another pressure gauge, one that you screw onto the boiler drain. Use a 30 psi gauge

    There us a chance, a good one, that the boiler gauge is not reading correctly

    12-15 psi is adequate for two stories above the boiler. How tall us your building, the approx distance from that gauge to the highest piping?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Thanks for the quick response! It’s a two story house. The main floor is being heated fine. I would say the distance between the boiler and the main floor is about 10 feet plus 14 feet from main to top floor. Gauge could be a good idea. Have one you’d recommend? Hardware store I’m closest to is Menards.

    Also, I’ll do my best to get better pictures, but the boiler is in this kind of tight closed off area
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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  • Big Ed_4
    Big Ed_4 Member Posts: 2,832
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    You have a manual feed , the yellow and white ball valves are the shut offs . As HR said bring it up to 15# . Where is the expansion tank ?

    There was an error rendering this rich post.

    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Expansion tank is very close by. Showing the tank, pipe that leads to the tank, and view of tank from boiler room in pictures. 
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Big Ed, if I’m interpreting your comment correctly, that means I use the shut off valves to increase PSI? Looks like I should open yellow first and then white?
  • Big Ed_4
    Big Ed_4 Member Posts: 2,832
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    You have two in series , open one and throttle the other . Drain the expansion tank first. It is a old habit ......

    There was an error rendering this rich post.

  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Just making sure. Does this picture show the series you’re talking about? Also, I know what opening means, but what do you mean by throttle?
    I drained the expansion tank about a month ago. Think that’s recent enough? I need to shut off the valve that goes to it before draining, correct? And then open that again before opening and throttling?


  • HVACNUT
    HVACNUT Member Posts: 5,888
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    It looks like there's no pressure reducing valve, so by throttling, @Big Ed_4 means once the White valve is open, open the yellow valve very slowly and watch your new gauge. Without a PRV it might build pressure very fast and blow the relief valve. Do not go over 25 psi.
    There's a lot of volume in that system so it will take time to bleed the rads.
    If someone can throttle the valve to keep the pressure up while someone else bleeds the rads, it'll go quicker, unless you love your cardio.

    P.S. By previously draining the expansion tank without adding new water and pressure to the boiler, you inadvertently caused an air lock.
    Minnesota4114
  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    Your expansion tank plumbing connections and location are a bit iffish but it will work there -- though you may have problems with it waterlogging.

    When you drain it right down, make sure that the connection to the rest of the system is valved off. Then close the drain and reopen the connection to the rest of the system. Now since that is a compression tank, it needs to have that connection to the rest of the system at a high point (preferably with an airtrol or other special fitting to capture air). Further, there must not be any other air eliminators on the system, although a modern plumber or less well educated heating man may want to install them.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Got it, I think I understand, but just going to write it all down to make sure that I’m right.

    Sounds like I need to completely empty my expansion tank before I do this. In order to do that, I’ll close off the rest of the system to the tank and reopen that connection after it’s emptied.

    Then I’ll open the yellow valve and toggle the white slowly while checking the PSI. I’ll have someone upstairs going around bleeding the radiators while I do this. From what you said, it seems possible that the expansion tank will become too full during this process? I’m guessing in that case, we’d have to pause, close off the pipes to the tank again and empty again before continuing? If this understanding is correct, will hopefully be doing this tonight.

    Jamie, I’m a bit confused by the high point part of your post. Do you think we need to change or add a fitting on the connection between the boiler and the expansion tank?
  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    A minor bit of confusion. I don't think you need to have the expansion tank closed while you are trying to purge the rest of the system. If you reopen it, it will be a lot easier to maintain pressure.

    On the second point there, what fitting -- if any -- is at the connection between the circulating part of the system and the pipe to the expansion tank?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Got it, sounds good.

    This is where the pipe that leads to the expansion tank meets with the boiler.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,840
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    @Minnesota4114

    If you have 10" to the first floor and 14 to the second floor (plus uou should have 3-4 psi at the top for margin) so 15PSI should be enough. When you bleed the top floor radiation with the pump off and you have a little pressure at the bleeders then your ok
    Minnesota4114
  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    The pipe to the expansion tank is the one going off to the right, with the yellow handle valve on it?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    That’s correct, Jamie. Sorry should have specified 
    OilfieldHippie
  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    I was worried you would say that. Honestly, that arrangement is not going to work well if at all. You will probably find it much easier to get a relatively inexperienced person to install a bladder type expansion tank on that line and discontinue using the old compression tank. You'll also need to add air removal equipment.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114
  • neilc
    neilc Member Posts: 2,716
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    take another look at the original pictures @Jamie Hall ,
    there's nothing above that tank line except the relief valve,
    at worse some air in under the relief,
    tank line is probably ok as long as there is some pitch to tank,
    Yes? No?
    known to beat dead horses
    Minnesota4114
  • hot_rod
    hot_rod Member Posts: 22,479
    edited November 2023
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    With expansion tanks you end up with one of two systems.

    Air Management. A plain steel tank that has both air and water in contact. You needto "manage"or maintain that air bubble in the compression tank. To do this properly requires a fitting in the tank, and a fitting in the boiler, properly piped.

    The second is Air Removal. You have a tank with a rubber divider between the water and air. This allows you to put air elimination devices on the system to get all the air expeled.

    Your system is a partial attempt at an air management system, lacking some of the finer details.

    I agree with Jamie, get a diaphragm tank and good air separator installed.

    It is getting harder and harder to find plumbers that truly understand air management systems and the proper components. And they can be expensive to build and install.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Minnesota4114
  • Minnesota4114
    Minnesota4114 Member Posts: 10
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    Just giving an update. Raising the pressure in the system worked well, and now our radiators on the top floor are hot.

    As for the diaphragm tank and air separator, how pressing of a need are these things? Could I wait a year or two? Or should I do this ASAP? Just spent a lot on some other projects, so just don’t have a ton in the budget right now. Any ballpark guess of what having that done might cost?
  • neilc
    neilc Member Posts: 2,716
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    and the tank is missing its airtrol and may not be performing at its best,
    known to beat dead horses
  • Jamie Hall
    Jamie Hall Member Posts: 23,653
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    Just giving an update. Raising the pressure in the system worked well, and now our radiators on the top floor are hot.

    As for the diaphragm tank and air separator, how pressing of a need are these things? Could I wait a year or two? Or should I do this ASAP? Just spent a lot on some other projects, so just don’t have a ton in the budget right now. Any ballpark guess of what having that done might cost?

    So long as it is working OK, leave it be.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Minnesota4114