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HRV system filling with water/condensate

  • 19-03-2020 10:23am
    Registered Users Posts: 20 s00bf06e


    We have a vent axia sentinel HRV system installed in our new build which is in place about a year and a half. A few weeks ago I woke up during the night to hear a noise from the system that sounded like churning water. The motors run at 20% at night and 45% at day. I turned it off and called the plumber who installed it the next morning. When he arrived we checked the system (located in the attic) and found the chamber where the exhaust fan is full of water. We followed the exhaust pipe to where it exits through the slates, the last 30cm of duct between the rigid duct and the roof vent is flexible and this was sagging down and full of water. This happened when we were having all the storms and the roof faces directly south and was taking the brunt of this weather, the plumber thought driving rain must have come in and collected in the duct and HRV unit. He came back two days ago and reconfigured the ductwork and put in a condensate collar to trap and collect any rain water that might get blown in. This morning I heard a similar churning noise in the system and went and checked it and the exhaust fan chamber again contained water. So now I think this is condensation building up for some reason. The ducting is insulated and there was no great wind or rain in last two days. Does anybody know of a solution to this?, are our fans running to slow for example or could it be something to do with the humidity sensor. I will ring the plumber again but I am going to see will it happen again over the next day or two. any help appreciated


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion

    That is a normal operation of a HRV.
    The fact that is creating troubles is the plumber's understanding of the piping rather than a issue of the unit.

    See my graphs... big hit on the humidity to take on.
    80ish outside converted to a 33% indoors...


    Take care.

  • Registered Users Posts: 4 MrBob

    I have had similar issue with my vent axia. The issue was due to the small drain hole inside the unit being blocked, it was due to dead bugs getting into the intake and only happened in very humid weather

    I was able to remove the vent pipes from the top and reach into the unit to clear the blockage with a small bit of wire. It is very awkward but possible.

    If you are unable to do that, then you can manually drain the water from front of the unit as there is a second drain hole

    Let me know if you need more info and I could try to get some pictures if you are really stuck