Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Dunkirk dcb 125 boiler slowly losing pressure

JDPT
JDPT Member Posts: 8
in THE MAIN WALL

about a month ago our 5 year old Dunkirk dcb 125 boiler was flashing low hydraulic pressure. It eventually locked out with the low pressure code as we waited for HVAC help. Topped it off, pressure back. We have inspected any visible areas for leaks and found none. Hvac tech and plumber have since tried several things, replaced old expansion tank and auto vent, completed maintenance/cleaning on heat exchanger , burner, and flame sensor, replaced PRV (noted build up inside pipe when removed), and flushed the system. We do have one room that is pex in slab radiant heat (wouldn’t see leaks) and it seems to be heating up well, I have noticed that the return flow temperature is barely increasing. The pressure has continued to slowly decrease especially when the system is not running, not yet flashing though. Maybe block the radiant floor zone and see what happens? Any other suggestions would be great! Thank you

Comments

  • Ironman
    Ironman Member Posts: 7,539

    Do you have an indirect water heater?

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • JDPT
    JDPT Member Posts: 8

    yes!

  • Intplm.
    Intplm. Member Posts: 2,176

    This is a mod con that has a loop under a slab? If you can isolate that area/valve it off and look to see if that shows where the leak is.

  • JDPT
    JDPT Member Posts: 8

    Shutting down the floor valve is probably our next investigation. However, I didn’t think of the indirect water heater . It is an old 41 gallon Amtrol that is not showing signs of leaking, however, I have noticed that it seems to call for heat during every shower (empty nesters so only 2 of us). Could issues internally cause pressure loss in the boiler system?

  • Intplm.
    Intplm. Member Posts: 2,176

    If you can safely isolate the areas mentioned, you might find the source of the loss of pressure.

  • GGross
    GGross Member Posts: 1,258
    https://forum.heatinghelp.com/discussion/comment/1821736#Comment_1821736

    I wouldn't rule anything out, but a leak on the domestic side won't affect the heating side, and a leak on the heating side (inside the boiler mate) would cause your boiler pressure to rise not fall, since the Domestic pressure is basically always going to be higher than the boiler pressure

  • JDPT
    JDPT Member Posts: 8

    thanks for the information. I appreciate your expertise

  • JDPT
    JDPT Member Posts: 8

    My plumber just told me the same thing in regards to the indirect water heater. We are currently isolating the radiant floor heat. I did ask my plumber if it could be something internal leaking and he said that we would see water inside and/or around the bottom of the boiler. We shall see how this goes….

  • Ironman
    Ironman Member Posts: 7,539
    https://forum.heatinghelp.com/discussion/comment/1821772#Comment_1821772

    Yes, it would cause the boiler side to rise which in turn would cause the relief valve to dump…

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,312

    To isolate an area takes 2 valves.  Closing one valve only prevents heat from moving in that zone/area.   It does not prevent water movement to that area thru the other end of the zone   The following valve arrangement will not enable you to isolate the pressure of the boiler to the leak location.

    Screenshot 2024-11-23 at 4.32.33 PM.png

    Valve on supply only.

    Screenshot 2024-11-23 at 4.30.57 PM.png

    Valve on return only

    Ths is the only way to isolate the boiler pressure from a suspected leak area.

    Screenshot 2024-11-06 at 5.26.06 PM.png

    A valve on both the supply and the return will keep boiler pressure from going to the area you are testing by the process of elimination to locate where the leak might be.

    As an added note … if the indirect water heater coil has a leak, then the boiler pressure would probably increase. So that is the last place I would look for a leak where you are loosing pressure.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Intplm.
  • JDPT
    JDPT Member Posts: 8
    edited November 24

    yes, and thank you. he shut off both the supply and return to the floor. After about 25 hours of the floor off, the pressure is continuing to slowly decrease as it has been. Is it possible for there to be a leak inside the system that could leak and not show up at the bottom of the casing? Now I am starting to get really concerned….

Categories