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pressure fluctuation

maubin
maubin Member Posts: 11
in Radiant Heating
Hi

I have a Monitron Boiler and worked fine until I turned off all loops except one; the pressure goes way down when system/boiler is not running (asking for heat) and when it does the pressure goes back to 20 psi.  The pressure gauge was always steady before that.  Any ideas?



Thanks!



Marc

Comments

  • Gordy
    Gordy Member Posts: 9,546
    Pressure drop

     Why did you close all the loops except for the one?  Was there problems before?
  • maubin
    maubin Member Posts: 11
    Pressure fluctuation

    No not really I just didn't need the other loops at this time. Before I turned them off the pressure was fine.
  • Gordy
    Gordy Member Posts: 9,546
    Okay

     So when there is no heat call what is the pressure with all loops closed except the one? 
  • maubin
    maubin Member Posts: 11
    Pressure drop

    It goes to around 10psi
  • Gordy
    Gordy Member Posts: 9,546
    edited March 2011
    My thought is

     The system is seeing more fluctuation due to the smaller volume with only one zone open.



     If it does not drop below 10 then there is no leak.  Have you checked the X tank to see if the pressure is correct? Should be 12 psi disconnected from the system. If you do not have more than 2 stories.



     Seems like an odd way to control zones. Why the manual disconnect of the zones?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    edited March 2011
    Could be head pressure as well....

    Is it pumping away from the expansion tank, but into the boiler?



    Does the pressure JUMP from 10 to 20 or increase gradually?



    Got pictures?



    ME

    There was an error rendering this rich post.

  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    Hi

    Got home tonight and the boiler pressure gauge was reading between 5 and 10psi.  Than a little later the system called for heat and the reading @ 150F with a pressure reading of 20psi. (see picture).  The pressure doesn't jump it increase more gradually along with the  temperature going up.    Could it be the X tank?  The way the system was put together doesn't not allow me to check the x tank pressure while disconnected.   Is there any other way to check the x tank pressure? 



    Thanks!
  • Gordy
    Gordy Member Posts: 9,546
    wider angle pic

     Got a pic of how everything is plumbed to the boiler?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    All indications are...

    Bad expansion tank.



    If it WAS stable before (or relatively so) and is jumping all over the place now, it indicates a loss of diaphragm pressure. It is still not in dire straits, but needs attention.



    Make sure and give it isolation and pressure release capabilities. Watts makes a perfect device for doing this.



    ME

    There was an error rendering this rich post.

  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    I checked the x tank and when cold and there was no pressure in it so I added 12psi to it which brought back the system to 20psi.    If it doesn't work I will replace the x tank and add a valve to it to allow isolation.   I will take a picture of the system a little later.



    Thanks for the help here!
  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    Well after putting 12psi in the x tank and calling for heat the pressure gauge went up to 30psi so I turned everything off.  Maybe I need to empty the system of all water and then add pressure the x tank?    Or just replace the x tank?   Can I use a x tank for potable water that I can buy at the big store?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Yup...

    In order to properly check the air side and or charge the air side, the water side MUST be a ZERO psi.



    Get ready for a wet mess.



    As you are pumping air into the tank, water will be coming out of the tank and this water MUST be let out, or your efforts are for not.



    After total recharge, you can expect some increase in pressure when all zones are heated up, unless the expansion tanks is GROSSLY oversized, which I doubt.



    If you see any water on the air side, the tank is shot and needs replaced.



    Grab your scuba gear.... Obviously, the make up water should be turned off during this procedure.



    ME

    There was an error rendering this rich post.

  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    I have my wetsuit on ;) ...So I will shut off the remaining zone (isolate the boiler, tank etc) and remove the water from the system then add pressure in the X tank ( which is model Extrol/Amtrol #15) to 12 psi.   Refill the system with water until the boiler pressure gauge indicate 20 psi and then open all zones and call for heat.  Does it sound like  good plan?



    I haven't seen any water on the dry side of the x tank so it might still be good? 
  • Gordy
    Gordy Member Posts: 9,546
    edited March 2011
    boiler pressure

     You almost have it right. When you refill the system the boiler gauge should read 12 psi also. So 12 psi in the x tank, and 12 psi at the boiler gauge when refilling the system with water.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    # 15 tank...

    is the SMALLEST tank Amtrol makes.



    Let's see, the last time I saw a # 15 tank on a heating systems was... Wait a minute, I've NEVER seen anything smaller than a # 30 on heating systems.



    Expect an elevation in pressure when everything is hot. So long as you don't exceed 24 PSI, you should be fine as frog hair...



    Ribit.



    ME

    There was an error rendering this rich post.

  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    After purging the system and resetting the x tank at 12psi operation is normal. I put water in the system until the boiler pressure gauge reached 20psi; should I keep it at 12psi?



    The boiler is a Monitron EH-20 135-s perhaps I should change the X tank for a bigger one? I have about 2200 sf surface with 1/2 pex with oxygen barrier.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Bigger IS better...

    unless what you have works, then its irrelevant.



    Lower the PSI's to 12 and fire all zones and see what the pressure tops out at. If its below 24, then you're good to go.



    But keep an eye n it, cause the air pressure went SOME where...



    ME

    There was an error rendering this rich post.

  • maubin
    maubin Member Posts: 11
    pressure fluctuation

    Thanks to all!



    I'll reduce the pressure to 12psi and fire up the whole system and see what's up!



    Marc
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