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.

Terrible hotwater output from tankless combi unit

Options
I recently purchased a home with a Triangle Tube 125K BTU heating/hot water combi unit. This is for a 2000 sq foot house. Given the winter season, the heating has been running. The amount of hot water supply coming out of the hot water faucet side is terrible if I am running more than one faucet. For example, if the tub is running (btw, pressure doesn't seem to particular high for the water coming out), the sink in the same bathroom has a low supply of hot water until the tub sink is off. It's ridiculous. I can't see how this will sustain a family of 2 adults and 2 kids. Can this be repaired? Or is this how these combi units work? Even at 125K BTU, I would still think I can run heating, a shower and 1 sink at the same time. I miss the old fashioned tank water heaters!

Sanjay

Comments

  • Zman
    Zman Member Posts: 7,579
    Options
    You could verify that the unit is performing up to spec with a 5 gallon bucket and a watch. If it is you may want to consider low flow fixtures. If not, troubleshooting is in order.
    Haterusguy also makes a good point.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Jamie Hall
    Jamie Hall Member Posts: 23,455
    Options
    Troubleshooting might be in order -- but consider: Q = 500 X gpm X delta T. Equals 500 times 3 times 70 for your tub. Equals 105,000 BTUh right there. You can't get more than that out of your combi. They are meant for one bathroom and some heat; that's all.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • kcopp
    kcopp Member Posts: 4,443
    Options
    As the others have mentioned combi boilers have their limitations. There are always options. A storage tanks would be in order, if you have the room. BTW...how many baths in the place?
  • hot_rod
    hot_rod Member Posts: 22,271
    Options
    agree with mad hatter, you don't have enough "horsepower" to get more than MAYBE 3 gpm. If your incoming water is lower than 50°F, as many places are in the winter, expect even less performance.

    Solar pre-heat helps, but somewhat un-predictable.

    That being said, most of Europe, large and small families, get along with small tankless and comb boilers, a different lifestyle and water consumption.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    kcoppjonny88RobG
  • wogpa67
    wogpa67 Member Posts: 238
    Options
    you need to get your water tested. those small heat hx get fouled up easily
    icesailor
  • Jamie Hall
    Jamie Hall Member Posts: 23,455
    Options
    hot rod said:

    agree with mad hatter, you don't have enough "horsepower" to get more than MAYBE 3 gpm. If your incoming water is lower than 50°F, as many places are in the winter, expect even less performance.

    Solar pre-heat helps, but somewhat un-predictable.

    That being said, most of Europe, large and small families, get along with small tankless and comb boilers, a different lifestyle and water consumption.

    I would add to the most of Europe... at least in Scotland, what you will find is a tankless for each bathroom, if there is more than one.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SWEI
    SWEI Member Posts: 7,356
    Options

    most of Europe... at least in Scotland, what you will find is a tankless for each bathroom, if there is more than one.

    Often hanging on the wall in the bathroom (sometimes in the shower) where you can turn the knob to get whatever temperature you need. Piping becomes very simple -- one cold water line to the space.
  • hot_rod
    hot_rod Member Posts: 22,271
    Options
    right down the the simplest "electric shower head" device
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • icesailor
    icesailor Member Posts: 7,265
    Options
    Stinky Europeans.

    Do they have GFCI's on those? In the USA, they would at least have that lamp cord in Liquid Tight tubing and fittings.
  • hot_rod
    hot_rod Member Posts: 22,271
    Options
    Do't know about GFCI, most are 230V if that makes you feel better :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    Options
    They call them RCD's -- and yes, they are mandated for many applications.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    Options
    230 V-now I feel better!--NBC
  • icesailor
    icesailor Member Posts: 7,265
    Options
    SWEI said:

    They call them RCD's -- and yes, they are mandated for many applications.

    "RCD" ??

    What's that.

  • SWEI
    SWEI Member Posts: 7,356
    Options
    Residual Current Detector (Brit-speak for GFCI.)
  • icesailor
    icesailor Member Posts: 7,265
    Options
    Damn Brits. Why can't they just learn English like we speak over here. That thing they speak across the pond is all gibberish.
    kcoppjonny88