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Navien 240 combi installed - I have concerns

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  • Tdubx
    Tdubx Member Posts: 16
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    Piping

    Here's an update, i didnt get the pressure valve tester (yet), my plumber is going to get me one and i'll test what I currently have to the house this weekend. As for the water lines. The water main sits on the city's side, so it was their responsibility to change and upgrade it. At that time (1989) they did a pressure test and concluded 110# at the main.



    More recently, i went around the house to check my PRV and noticed that I actually have a 3/4" line from the city side to my PRV, then a 1/2" into the house, and ultimately connecting to the navien. So, my plan is to upgrade the 1/2" line that site just outside my house, I wont have to dig up and concrete or foundation since the line is actually run on the outside of the house in contained area, so this should be relatively easy to upgrade. At that time i'll re-test and see what I have for pressure. Everything seems to lead to the 1/2" line coming into the house and/or the PRV.



    And yes, in the house I have 3/4" to 1/2" PEX to the fixtures.
  • Gordy
    Gordy Member Posts: 9,546
    edited March 2014
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    Thank you

    I knew ther was a 1/2" bottle neck in there somewhere from the street to inside the house.



    Still a little confused when you say 1/2" runs off the prv to the Navien. So the cold side is 1/2" to Navien, and all cold side on fixtures. So when you ran new 3/4" pex you tapped into the 1/2" for your distribution lines of 3/4, and then back down to 1/2" to the fixtures?
  • Snowmelt
    Snowmelt Member Posts: 1,418
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    In the mean time

    Are you going to do the work yourself, I suggest you look up static and dynamic pressure.



    Also whatever you replace use one inch copper or 1-1/4 pex you want volume
  • icesailor
    icesailor Member Posts: 7,265
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    Getting confusing:

    This is getting confusing.

    First of all, no matter what size water pipe you have going to a fixture (except shower valves and tub valves), they all reduce down to 1/4" ID Tubing. The current El Cheapo PB spaghetti risers are even smaller. Even if you ran 2" copper to under the sink, the fixture is still fed by 1/4" ID tubing.

    Although it is nice to have 1" run all over, it is commonly accepted installation practice to use a majority of 1/2" tube/piping in residential installs. Its nice to go bigger if you can afford it. Its nice to be competitive for jobs.

    Massachusetts is as middle of the road as you can get. The minimum water service size is 3/4", even if it only serves a toilet. I don't know how cold it gets where this house is but if Canada, I'll bet the service is 4' down. Not a recital of the Earth Guitar Band. As far as checking the pressure, go to your local supply house and pick up a 0-160# 1/4" Bottom gauge and a 1/2" X 1/4" Reducing coupling or ell and a 1/2" boiler drain. Plus a washing machine hose. Connect it to any boiler drain you can find and turn it in. That will be the pressure. Let it flow, check the pressure. Its not expensive science.

    Before you go nuts and start re-piping the house, check the PRV. It isn't working properly.

    My Florida place is all 1/2" copper with a 3/4" copper service. The city maintains at least 60#. The pressure doesn't go up or down. But because of El Cheapo Moen 1982 Moen single lever Non-Pressure balance valves, if anyone turns on a faucet, you immediately feel it in the shower. Like I said in an earlier post, the Pipe Du Jour is now, 1/2" PEX, with home runs from a fixture to a manifold. Plumbing, heat and gas. 1/2" piping is the rule of the day.
  • Snowmelt
    Snowmelt Member Posts: 1,418
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    Iceman

    I'm going to have to disagree

    Take your 1/2 pex and take my 1 inch copper

    Open 4 fixtures in your home

    I know what will happen but I want you to tell me?
  • Gordy
    Gordy Member Posts: 9,546
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    So if your 3/4" line

    Has a 1/4" kink in it from the street to the house that does not make a difference?



    This could go everywhere. My point is if your using multiple fixture simultaneously you need volume to the fixtures the closer to the fixture you reduce down the better. It would drive me nuts to have to use one fixture at a time or there will be war crystal from the shower stall.
  • Tdubx
    Tdubx Member Posts: 16
    edited April 2014
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    ICESAilor: Your thought process...

    ...is the same as my plumbers too. He said we can run 3/4" in the whole house, then 1/2" down to each fixture It's all about volume, which will give you the right pressure.



    If we are already getting low volume from a 3/4" line from the city side to our final run of a 1/2" line to the Navien, then we've already lost volume, resulting in lower pressure. No matter what we do inside the house, won't help.



    My area doesn't get colder than 30F (or minus 10C) and my lines run down about 2ft, not 4ft so I can access them quite easily.
  • Tdubx
    Tdubx Member Posts: 16
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    Let me explain..

    From the street the lines are 3/4", then on the outside of the house (before the PRV) they change to 1/2". At that point the 1/2" line goes into the PRV, then inside the house. So, ultimately, the 1/2" gets connected to the Navien (as per my picture above).



    What I meant was, the new lines from the Navien were all 3/4" (those are all in the attic), then the runs down to each fixture are 1/2" (those are smaller runs of no more than 10ft).



    Hope that makes sense.
  • RobG
    RobG Member Posts: 1,850
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    Don't forget

    Don't forget the pressure drop through the Navien. The 1/2" main and the pressure drop through the heat exchanger is a recipe for dissatisfaction.



    Rob
  • HDE_2
    HDE_2 Member Posts: 140
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    Not on a combi

    Domestic flow is through a plate heat exchanger so, pressure drop is minimal, maybe 5 psi at 5 GPM?