Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

High Efficieny Gas Boiler Recommendation

esabetesabet Member Posts: 1
We are in the midst of constructing a single family house on Long Island, New York.

We are looking for advice on sizing of the boiler and brand recommendation.

The primary source of heat is through Forced Hot Air and there are 6 Zones in the house.  As a secondary source there is also radiant heating in selective areas of the house, i.e. bathrooms, main foyer and 1st floor living quarters.  Here are the BTU demands/requirements that we are aware of (do need help with BTU calculation for the Radiant Heating):

        1) Hot Water Coils, total for the 6 zones is 360,000 BTU.

        2) Radiant Heating:  Total Square Feet of radiant heating is 5,300 S.F.

        3) Garage Heater w/ Hot Water Coil, 45,000 BTU.

The house is Energy Start Compliant with foam insulation and high quality windows and doors.

We are strictly interested in High Efficiency Boilers.  That said, and to be more specific, our questions are as follows:

       1) What size Boiler(s) would you recommend?

       2) What Brand/Manufacturer would you recommend?

       3) What is your opinion about Alpine vs. Knight Heating Boiler by Lochinvar?

Thank you in advance.


  • kcoppkcopp Member Posts: 2,746
    Was a heatloss...

    done? Where did you get that 360,000 btu number....that is HUGE! Either that is one huge home or there is no insulation in the walls.
  • SWEISWEI Member Posts: 7,356
    Energy Star Compliant

    If true, that 360k rating on the coils might be at 180 or 190F.

    What is the heat loss calculation?
  • ZmanZman Member Posts: 3,478
    edited June 2013

    The first thing to understand is that number  of  BTU's that your coils are capable of emitting is not the same as the number of BTU's your house will loose on the coldest design day(heatloss calc). Your boiler should be sized for the latter.The home you describe should come in at less than 20btu/ft.

    High efficiency boilers perform best with low water temps. The entire system should be designed perform at low temps. It may be that your designer has oversized the coils to achieve this.

    Trying to integrate forced air and radiant floor heating is tricky.The whole idea with the radiant is to have warm toes. If you keep the floors warm for your feet, you really don't need the air.

    The heat exchanger in the lochinvar is "hands down" superior tovAlpine

    Given the scale of your job, and the fact you are still in the design phase, I would get a top quality contractor on board now and rest easy. There are several great long island guys on this site, I would start with Robert O'Brian.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomeOwner1HomeOwner1 Member Posts: 134
    We are happy with our Modulating Condensing Boiler

    We have baseboard in our house and is about 1400 square feet smaller than yours but has vaulted and high ceilings in about 75% of the home. We are in Cherry Hill New Jersey, so similar climate.

    We chose a Navien Ch-240 and does great, modulates down heat for better efficiency. They can be cascaded and connected together as well to serve larger needs. These units do both hot water and heating all in one. Also can be used as a hybrid feeding forced hot air coils, radiant and baseboard all in one shot. Trangle Tube makes some nice ones too, but are more money and the combis would never meet your hot water needs. Indirect heating tanks then would be an option as well with any mod con brand boiler.

    The Navien could potentially be the solution with the least equipment costs though. You may be able to get away with a sinlge unit, but let your contractor advise you of that. Also, probably the smallest space taking option as well. And potentially the least expensive. Some people are not fans of the brand on this forum, but that is the only combi that I am personally aware of that sizes to meet these needs. We did a lot of research. The professionals on this forum know best though. Interesting option nonetheless.

    The combi efficiency ratings are a bit misleading since the heating side runs around 97 to 98% efficient and hot water runs 87 to 92% efficient from what was explained to me on most combi systems. Hence, your combine rating is usually in the low 90's in those types of boilers.

    The guys are right though, we had to measure our flow rates for hot water to make sure our selected option would work and also have someone come in and figure our your max heat loss on the coldest day of the hear so your unit actually does the job and not too big.

    Just a heads up, our heat loss was determined to be only 80 to 90 KBTU in our home, which is only probably rated for insulation at average to high average at best. This was done with the door blower test and full analysis. Your measurements and estimates don't sound right to the layman here. We have 4 thermostats piped to seven total loops driven by three 1/12 HP circulation pumps.

    Our previous system was a way over-sized wet base boiler and we saw eye opening reductions in our bills when equipment was sized correctly.

    Good Luck!
  • ZmanZman Member Posts: 3,478

    I don't subscribe to the strategy of oversizing the heat boiler in order to get instantaneous DHW . Just to many compromises. Navian is a completely different boiler, much lower quality and price point.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomeOwner1HomeOwner1 Member Posts: 134
    We agree to disagree

    Works great in our house. The proof for us was in the very low gas bills.

    You need the bigger heat potential to meet the hot water side.

    Otherwise the unit modulates down to 17kbtu. It is not over-sized due to modulation and outdoor sensors.

    It works, it is proven and I own one.

    Too many people tried to tell us that combis are not feasible. IT WORKS!
  • ZmanZman Member Posts: 3,478
    I agree..

    Your system clearly works. You are saving energy over a conventional system.

    The 10 to 1  turndown on most units costs some efficiency you are less efficient than a 5 to 1 model in most cases.

    Navien does not have a particularly good track record over the long hall. They are priced accordingly


    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • heatpro02920heatpro02920 Member Posts: 991
    edited June 2013
    If you do indeed need that amount of BTU's

    If I were quoting your job {keep in mind I would do a heat loss, and I'm thinking your property is more likely under 200K BTU's depending on the property of course, without being there and doing the man. J I am guessing using my experience}...

    So we will do this 2 ways, if you do indeed need 360K I would be proposing...

    2- solo 175's and 1 solo 60, so thats 3 boilers, cascade the 2 175s and run the 60 for the garage... That will let you mod down to 50K on the house and 16K on the garage...

    Now I doubt you have that size load, so if you were more in the 200K range, I would say just 2- solo 110's, it will allow you to mod down to around 30K...

    Need more info though, like how many zones, what is the heat loss of the smallest zone, what are you doing for DHW, ect?

    But with that size load and in my experience larger homes have a lot of smaller zones and a lot of zoned space that doesn't get used.... So you need a good amount of BTUs but want to be able to mod down for when them small zones call...

    One more point- DO NOT GO WITH NAVIAN, they are not proving the test of time, the PROS in the industry are very aware of this problem... I know they are cheap initially, but you will pay one way or the other, Homeowner 1 is still a newly wed with his unit, time will harden him and he most likely will be singing a different tune when he tucks his kids in with no heat a few times...
  • JStarJStar Member Posts: 2,668

    Condensing boilers are not efficient on a Hot Water Coil system. The temperatures need to be way too high to allow for efficient operation.

    I would stick with an atmospheric boiler for the coils, and a condensing boiler for the radiant.
    - Joe Starosielec
    [email protected]
  • ChrisChris Member Posts: 3,056
    Heat Loss

    You have to do that heat loss. If this is an energy star home your probably in the 20 btu/hr area and may even less. Based on that your looking at a boiler that could heat a 18,000 sqft house.

    A condensing boiler will work efficiently on a hydro air system. Need that heat loss though in order to find the needed water temp at design. Have plenty running on 120 degree supply water temp.

    Having both the radiant (low temp) and hydro (high temp) systems I'd look at a Viessmann Vitodens 200. The boiler can control two separate heating circuits via controlling a 3-way mixing valve for the radiant. May simplify your control strategy.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • heatpro02920heatpro02920 Member Posts: 991

    I have a lot of efficient Hydro air systems out there using mod cons, especially since his sound so oversized he can probably run 130 degrees into each one... The huge supply return difference makes them awesome for mod cons, and his large heatloss also makes him a prime customer for the savings from a mod con...
  • heatpro02920heatpro02920 Member Posts: 991
    I know navian is technically a

    combi boiler, but IMO its just a tankless water heater with a 3way valve and a plate exchanger... There is a reason we stopped installing tankless water heaters with 3 way valves and plate exchangers..... Because they do NOT last, there is no such thing as a free lunch, I have had customers asking for navian units, and I talk always end up showing them that even a basic Condensing rinnai unit and with a small plate exchanger and taco 3 way valve will give them much better service life, better efficiency, and better support... Plus it is cheaper.. So if that is the way someone wants to go, I suggest going with separate components, buy a PE, a 3 way valve, and a rinnai ru98 at least you will really be up around mid 90's for efficiency.... And the over all cost is less...

    There is a reason a boiler of the same output is 3 times the cost of a navian and three times the weight.... you get what you pay for...
  • R ManninoR Mannino Member Posts: 422
    We Did a Boiler in a 5000 Sq Ft.

    house on Long Island, heat loss is probably around 100,000 btu/hr on a design day. FYI
  • HomeOwner1HomeOwner1 Member Posts: 134
    Are you saying Combis are inferior?

    Triangle tube also makes a combi. So do others.

    Are you saying all combi units built in the world won't hold up to a standard boiler?

    Also, Rinnai boilers are more than twice as much as the highest end Navien? Then, you either have to pay for a $1k indirect or at least a standard tank water heater. The ru98 is even more. That almost triples the cost.

    For a little more than the price of just the ru98 water heater alone, you could have everything up and running with a Navien CH.

    Also, as you already know, all of the combis out there, inclusive of the Navien, run higher for efficiency on heat and lower efficiency for hot water side, just like any hot water heating option. That 92% overall efficient rating is just a calculated weighted average between the two uses.

    It is NOTcheaper. Please don't mislead people.
  • HomeOwner1HomeOwner1 Member Posts: 134
    I agree as well....

    Yes, we did a lot of research on the recent history on units since their recent tweaked releases. Most of the bad press was on a unit they no longer sell with the copper heat exchangers. Now they just have the ASME and appear to have worked out tweaks over the years on the good model with the stainless.

    We spoke with some installers up north that have done about 30 or so of them in the past couple years. They indicated the newer 210 and 240 models are good these days. They appear to have turned a corner on quality these days and we live in the same town as the North East service center, which does not hurt.

    Even with another hot water heating option, you will still take an energy hit. And have more infrastructure to install and maintain. We did not have the budget to opt for a WM with indirect, which was triple the price for us.

    You are correct about price, for 2k you get a lot for your money.
  • HomeOwner1HomeOwner1 Member Posts: 134
    It is spelled Navien

    Spelling the name of the unit incorrectly consistently could give one the impression you are not familiar with them.

    I understand this board is very anti-combi and especially anti Navien, but it is a viable option if sized and installed correctly.

    If you only have an 80% cast iron boiler budget, you can indeed put yourself into a really nice high efficiency unit without breaking the bank.

    Is there a manufacturer that has never produced a heating unit that had some issues at some point in their lineage?

    A wet-based cast iron boiler will certainly be a simpler option but will not complete with the energy savings even in the short term on the mod con boilers. With expensive energy, the energy misers have payback quicker.

    Opinions on this board appear to be highly polarized. Most installers were trying to push us into another over-sized cast iron boiler, which would have ultimately led us to more higher then necessary energy bills. We are happy with our choice, time will tell as with any new technology to the market, to your point.
  • heatpro02920heatpro02920 Member Posts: 991

    how many times are we going to have this discussion, lol..

    Name the forums that are favorable of the units, for that matter get 3 owners on any site with units that are 8 years old and have not had any service issues...

    The NaviEns I have come across are trash, it is not a boiler IMO, it is a tankless water heater, you will do much better with a cast iron boiler over a naviEn. The units only get the 90% numbers at perfect conditions, you install that unit on a system with 180 degree supply temps and you will be lucky to get 85%, truth is you can expect to be in the 70's...

    I have a strong feeling Homeowner1 is affiliated with them, he lives very close to their headquarters and if you look up his posts on this forum, every one of them is him trying to sell a NaviEn, if he isnt affiliated, than I don't know what to say, for someone to give advice on a unit that he has not even had for a year is kind of wreckless, I install any units I am going to promote in my own property before putting my name on them, I take them apart, listen to the majority of users and installers and then commit to adding it to the lineup........... These naviEn units do NOT offer long term reliability... Buyer beware...
  • gennadygennady Member Posts: 677
    edited June 2013

    Energy star compliant and 360.000 + btu? Are you building an apartment building?
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • HomeOwner1HomeOwner1 Member Posts: 134
    Here we go again....

    Actually, was originally leaning towards a Triangle Tube originally until it was figured out that their units can't supply enough hot water to meet a typical household's needs. They have a long standing good reputation.

    The efficiency is good, as proven by our low energy bills. Probably would have been the case for all mod con boilers though.

    It is a boiler. Look it up.

    But, I ask you this. What combi boiler out there that can support a 3 bathroom typical suburban home with high flow rates like that unit can, support large home heat demands, plus for the same low budget?

    Please name just one.
  • ChrisChris Member Posts: 3,056
    Here's The Navien Story

    In my opinion. The reason for its popularity is price, plain and simple. They do a great marketing job and most homeowners are on tight budgets and can't afford the better products for the application. Any combi boiler, tankless or which ever name you want to put on it, best application is the condo, one bed apartment, cottages etc. The wear and tear in multiple simultaneous applications beats the living crap out of them.

    The misconception here is that the Navien cut your fuel bills. It's not the Navien its the technology of modulation/outdoor reset that cut the fuel bills. Like HeatPro and others have said, come back in 5-7yrs and let us know how much you spent on replacing parts.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • HomeOwner1HomeOwner1 Member Posts: 134
    Longevity question

    What about tankless water heaters that are standalone? Navien and other brands. Does that hold true that all tankless water heaters also face a short life due to quick thermal expansion conditions?

    Having a coupled dual use unit with a much lower temperature for heating does not seem to make sense that it would cause additional wear and tear due to heating exposure. It seems logical that the higher temperature hot water side would be the greatest point of expansion.

    Nobody ever said anything negative about the Triangle Tube higher end Prestige Excellence combi. Is that a bad unit as well that will face the same fate in your opinion of a short life because it is also dual use?

    True, the modulation options these days is really neat on boilers.

    As I have said, for us it was the option of a 80% cast iron boiler with coils built in for hot water or the Navien combi for the exact same price. You are correct, budget plays a big role. We were not willing to spend three times the money for a similar performing mod con boiler and hot water heating setup. Given the price difference, we could replace this unit three times over its comparable service life and still be ahead. I would imagine in your line of work, that is a tough sell scenario.
  • SWEISWEI Member Posts: 7,356
    Triangle Tube Prestige Excellence combi

    Has had plenty of negative comments -- mostly about its size (relatively large heating capacity paired with relatively small indirect tank.)  This is a challenge faced by nearly all combi boilers.
  • ChrisChris Member Posts: 3,056
    Kurt I Wonder

    What the markets opinion is going to be on this which will be avail here in a couple of

    months. My guess is that price point will dictate over the product itself.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • HomeOwner1HomeOwner1 Member Posts: 134
    Longevity question again

    Because the Triangle Tube Prestige Excellence is dual use for hot water and heat, does that mean it will not last as long?

  • HenryHenry Member Posts: 703

    Mod/con are ideal for the application. You do NOT need to run high temperatures into the coils at all times.

    Here is one of our installs of a large house. It has 3 tons of geothermal with a Knight KBN 285. The system provides hot water, heats the pool, heats the duct coil and 23 zones of geothermal.
  • HenryHenry Member Posts: 703
    edited June 2013
    500,000 BTU

    Here is one with a KBN500. It does snow melt, radiant in the garage area, domestic hot water, 400,000 BTU pool heater and a heating coil. Here is also the garage with a turntable to turn the cars, Wolfe BBQ and plasma screen!
  • ZmanZman Member Posts: 3,478


    I love the turntable. Where is the spring?

    I have always wanted to pull into the garage at 60mph. the energy would be absorbed by a giant spring. The car would be spun on a turntable and be released at 60. No wasted energy. Your project is so close.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!