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Navien NHB-150 vs. Bosch Greenstar 151

BIGRYE Member Posts: 2
I live on Long Island and I am in the market for a new boiler. Existing Boiler (NTI Trinity T150) is 13 years old and is on its death bed. Had 2 plumbers to my house for quotes on new direct vent boiler. One swears by Navien (he said he has taken their classes and has installed quite a few but has no experience with Bosch) and recommended the Navien NHB-150, the other panned Navien (said his company rips them out all the time due to a faulty heat exchanger, most likely to poor installation) and recommended the Bosch Greenstar 151. House was built in 2004 and is 3k SF, with baseboard heating and 2.5 bathrooms?

Thoughts on which one to choose and why? Don't mind paying more $ upfront if the unit I choose will end up saving me money in the long run.


  • NY_Rob
    NY_Rob Member Posts: 1,370
    Download the slant-fin app and do a heatloss analysis for your home- both units seem way oversized for a 3K SqFt house on LI.
    Most "modern" homes come in around 20BTU's/SqFt or less for heatloss, so your 3K SqFt house would only need 60K BTU's on the coldest day of the year. Installing a mod-con boiler with 2.5x the capacity you actually need isn't good for the boiler or your pocketbook.

    When I was looking into replacing my boiler in 2016, I looked at the Greenstar line. The knock on them is the heat exchanger is aluminum... not a great thing to have with the water here on the island.

    There are pros here who recommend Navien, also the Lochinvar KHN series may be a great choice for you or the HTP UFT80W may also fit your needs.

    There are quite a few members here who service LI, go to the main page and hit the "find a contractor" link. The pros here are generally head and shoulders above the locals in many areas.
    BIGRYE Member Posts: 2
    What about general rule of thumb that you should have 50 btu per SF? At 3000k SF these boilers would be correct size. Also, boiler being replaced also has 150k btu so I would want something comparable.
  • Brewbeer
    Brewbeer Member Posts: 616
    edited November 2017
    50 BTUs per sq. ft. Is about right for a turn of the 19th century Victorian with some of the windows left open.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
    BIGRYEkcoppJohn Mills_5Solid_Fuel_Man
  • gschallert
    gschallert Member Posts: 170
    BIGRYE said:

    What about general rule of thumb that you should have 50 btu per SF? At 3000k SF these boilers would be correct size. Also, boiler being replaced also has 150k btu so I would want something comparable.

    That general rule of thumb is total BS. The boiler you have is likely more than 2X the size you actually needed and might be the reason it's going to an early grave. Likely short cycled itself to death. I'd be shocked if you needed anything more than the 55 unless you don't have insulation in your walls or you keep your windows and doors open all winter.
  • njtommy
    njtommy Member Posts: 1,105
    edited November 2017
    Absolute max boiler is 80k btus for your Home. Heat loss will probably come up between 60k and 75k depending on how accurate you are entering the info. Most likely you will have a hard time convincing someone you only need a 80k boiler to heat your house. But that said the difference in bottom end modulation on the Navien and Lochinvar boilers is 8k for the 80k and 10k for the 100k not really a big difference, but 80k will be sufficient even with and indirect tank if you go that route.
  • NY_Rob
    NY_Rob Member Posts: 1,370
    @BIGRYE, just to put you mind at ease regarding how over-inflated that 50BTU's/SqFt heatloss figure is....

    My 1,700 SqFt home (built in 1964) on long island had an original 1960's era 100K BTU boiler which produced 80K BTU's output.
    I replaced it with a 80K BTU mod-con, but I have set the output limit on the mod-con to 50% so it can only put out 40K BTU's on max fire. We went through all last winter with the boiler limited to 40K BTU's output and it never fell behind leaving the house cold.

    My original heatloss calculation (when planning the boiler replacement) was derived from actual gas usage and it indicated my heatloss at 17-18BTU's/SqFt. Being that I can adequately heat my 1,700 SqFt house on the coldest day of the year with a 40K BTU boiler proves the heatloss calculation was fairly accurate.

    Your house is 40yrs younger than my house, I would be shocked if it wasn't tighter/better insulated. IMO, using a "guesstimate" heatloss figure north of 20BTU's/SqFt for your 2004 home is setting yourself up for another failed boiler install.
  • bob eck
    bob eck Member Posts: 929
    I like a condensing boiler or combi boiler with a Stainless Steel Fire Tube heat exchanger. Lochinvar Noble and Knight boilers, Burnham Aspen (K2FT), HTP, Bradford White, Laras, Triangle Tube there may be more that have this type of heat exchanger. When putting in a boiler to large for the job it will short cycle (turn on and off to often) and that will kill the boiler sooner than it should. Boiler needs to be sized right, piped in right, vented right and these three major things along with yearly maintenance your new boiler should run many many years.