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Baxi Luna HT pressure problem

We have a Baxi Luna HT 380.

About a month ago, we started getting an E119 (low pressure) fault code, and repressurized the system to alleviate the issue.  All was fine for several weeks, but it happened again today.  When we repressurized the system, it began to run normally, but the pressure, as indicated on the gauge increased rapidly until discharge came out of the pressure release pipe.  We used the small drain valve to drop the pressure, but it the pressure quickly increased again.  We turned off the supply for the DHW, and the pressure stabilized and ran the heat fine, but as soon as we open the supply for the DHW, the pressure increases, dumps water, then repeats.  What can be done to solve this?  Does it need to be bled somehow?


  • kcopp
    kcopp Member Posts: 3,772
    sounds as if....

    the pressure reducing valve/ fast fill has gone a bit wonky....  Typically it is a Watts 911s or 1156f. Sounds like that needs to be replaced.
  • jamesnichols3
    jamesnichols3 Member Posts: 2
    Which problem?

    Is your response in regards to the low pressure fault code itself, or the fact that it keeps ramping pressure and dumping water?  Really desperate to get DHW going again and deal with the low pressure problem later. 
  • RobG
    RobG Member Posts: 1,850
    Expansion Tank

    It sounds like the expansion tank bladder has blown. When the bladder broke, and the air from it was removed from your system it shut down on low pressure. When you refilled your system there was no where for the expansion to be absorbed and the relief valve popped.

  • gennady
    gennady Member Posts: 829

    on the right hand side looking from the bottom you will see round blue color valve handle. make sure it is closed tight and not leaking. for some reason baxi luna ht 380 has a manual feed build in and there is no backflow device or auto feeder build in. it is just a valve. We usually install auto feeder air eliminator and additional expansion tank separately and keep baxi feed valve closed tight.
  • Tom_133
    Tom_133 Member Posts: 747

    Baxi HT 380 expansion is one known weak point, so as gennady said it's good to put an external expansion tank on. The one fly in the vasoline in this is when the boiler is making DHW it has an internal check valve that in effect closes off the heat side and makes the internal expansion tank critical. So sometimes according to Baxi adding an external expansion won't solve the problem all the time, you may need to change internal tank as well.
    Montpelier Vt
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