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Low Volume - Rinnai RU199ip

kparker
kparker Member Posts: 3
in Domestic Hot Water

1.5 year old unit has been descaled and flushed. However, hot water volume is considerably less than it has been in the past. I removed and inspected the water flow servo valve, and it looked brand new. Used a garden hose and reverse flushed the unit for about 15 minutes to make sure there wasn't any sediment build up.

What could I be missing?

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,527

    What exactly do you mean by low volume? Does the temperature of the water change when multiple fixtures are is use?

    Have you tried calling Rinnai tech. support at (800)621-9419? Have your model and serial number ready.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • GGross
    GGross Member Posts: 1,592

    If it is a pressure issue I would start at the source and work your way to the fixture.

  • kparker
    kparker Member Posts: 3

    By low volume, I mean a low total volume of water. Heater heats fine, but the flow used to support multiple fixtures at once at a greater flow each than I can get out of one fixture. Aerators have been replaced, water heater has been descaled with vinegar and reverse flushed for about 20 minutes. Not a pressure issue because I don't have the same problem with the cold water. I am thinking it might be an issue with some type of solenoid or servo in the unit. Haven't called Rinnai yet, I guess that will be my next step.

  • mattmia2
    mattmia2 Member Posts: 13,855

    is there a strainer somewhere in the tankless water heater or elsewhere in the system?

  • pedmec
    pedmec Member Posts: 1,237

    Did you clean the cold water inlet strainer?

  • GGross
    GGross Member Posts: 1,592
    https://forum.heatinghelp.com/discussion/comment/1861768#Comment_1861768

    start at the source and work back to the fixture in question. What is the incoming cold pressure? are there any sorts of pressure drop between the cold line and the heater? (this includes any filter of any kind, softener, etc!) then at the tankless you did a flush, did you flush for around an hour? did you take out and clean the cold water inlet filter? If there is a drain after the heater you can screw on a garden hose adapter with pressure gauge and see the pressure drop through the unit, it naturally has some drop but you can check just how much. Once the unit and the incoming lines are cleared you move on to the piping to the fixtures, and then the valves in the fixtures themselves. I would be surprised if it were "some type of solenoid or servo" Seems like this is a standard tankless water heater, and not a combi, so there should be no reason to have internal valves close off flow at any time, they shouldn't be in there. There should be a flow sensor, some temp sensors, and the parts for ignition. the trouble areas for flow are the heat exchanger and filters either internal or external.

  • kparker
    kparker Member Posts: 3

    Cold water inlet strainer was cleaned when I descaled and flushed the heater. It's not just one fixture. The issue affects all of the fixtures. I don't think there is a pressure differential because when a fixture such as a lav is turned on, there is a quick rush and then the flow settles down at a much lower rate than we previously had. Something in the heater is choking the water flow and I can't determine what that thing might be.

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