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Who makes modulating non-Condensing Boilers

Ted89Ted89 Member Posts: 5
New to the wall.  Am planning a conversion from oil to N.gas.  Have a 6" SS lined chimney in Maine and  finned element radiators.  At the current gas price, I'd only be savings less than a hundred dollars a year with condensing efficiencies (even if they could be achieved, without adding 70% more radiator length to accept low water temps).  So,  I'm looking at non-condensing gas boilers.

I've only found one manufacturer of a modulating non-condensing gas boiler so far.  Space heat loss is 70k BTU/h and a 41 gal. indirect tank heater and my shower useage at only 2GPM hot would indicate DHW load of maybe 100k-120k output needed.  That's the boiler output I have now and the DHW is acceptable.  Unfortunately the two smallest of three space zones are BOTH only 14k each.  Without a modulating firing rate, a typical 130k output boiler would be short cycling wicked delivering only 14k. 

What other brands are out there that installers like installing.  Is it not offered because it's too expensive a feature to be bundled in a low cost boiler?

Thanks,  Ted


  • Aaron_in_MaineAaron_in_Maine Member Posts: 313
    Buffer tank

    The boiler should be sized to the heat loss of your house. With a zone that small I would install a buffer tank to keep the boiler from short cycling.
    Aaron Hamilton Heating
    [email protected]
  • RichRich Member Posts: 2,243
    Hey Ted

    check this out . May just fit your bill . Boiler , buffer tank , tankless water in one unit . Made in Mass , never had a problem with this HTP combi equipment . Just an idea .

    Video demo .

    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • TomTom Member Posts: 458
    My 2 cents...


    I am currently installing Weil McLain GV90+ boilers, they are basically the same as the old GV90's and those boilers are absolutely bullet proof. This new design adds an external heat exchanger which allows for a couple more passes of the flue gases (7 total) to absorb the heat. The vent pipes in PVC and the GV90+3 is right around 92% all the time and it condenses about an a gallon per hour of run time. No modulation but it can have outdoor reset if you decide to buy it, the sensor is extra. Inexpensive and cheap to install, I love it and works very well in applications that have existing baseboard.
    Montpelier Vt
  • SWEISWEI Member Posts: 7,356
    Don't obsess over non-condensing

    With those numbers, I'd probably specify a Lochinvar WHN-085 with an indirect hot water heater.  Minimum modulation is 17k, but if you tune the outdoor reset properly and use the zone thermostats as high limit controllers, you shouldn't have any "single zone calling" events.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    gas boiler

    the lochinvar solution does some modulation, has provision for outdoor reset, and looks a lot lighter to move down the stairs into the basement.

    download the slant-fin heat-loss software to figure out your size.--nbc
  • ChrisChris Member Posts: 3,056
    edited June 2013
    Don't Be Blind

    Think long term not short term. How did you come up with you need 70% more radiation? For this discussion let's say I buy the 70%. It's not more radiation its btu/hr with a lower water temp. Standard residential baseboard at a 1gpm flow rate with 180 degree water will delivery 560 btu/hr or maybe more depending on brand. For the most part 560 is what it is. So you have 10' of board that will produce 5,600 btu/hr. What if I just changed that piece of board out to a higher capacity board. With 160 degree water I move the same btu/hr as that residential board with 20 degree less water temp.

    Now under design conditions, that coldest day of the year I'm returning 140 degree water. Just 10 degrees from condensing. Where do you think that boiler will be running 90% plus of the season? Condensing mode.

    Look for the condensing boiler for this year and save your pennies and change out the existing baseboard the next year. Think long term not short term. You will not need to disturb any piping your using the same footprint. Did it in my house and went from needing 180 down to 150 at design..

    Look at all your options.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Ted89Ted89 Member Posts: 5
    Sorry, I don't understand your point

    I guessed at the 70% more radiator length if I used a condensing blr.  Slant Fin 30 baseboards at 2GPM 180 (cold day with a ODR) is 600BTU/ft. and at 140 (to return to blr at about 135) it's 330 BTU/ft.  Wouldn't I need actually 80% for length to produce the same amount of space heat?

  • Ted89Ted89 Member Posts: 5
    80% more

    Meant to type "80% more length".
  • ChrisChris Member Posts: 3,056
    edited June 2013
    There's No Guessing

    In hydronics, its all in the math. The heat loss changes. If your at 70,000 at design and let's say it's zero, what's the heat loss when it's 32 degree out? 38,0000....So what water temp do I need. I have no idea how many feet of board you have. You have to break out each zones heat loss and do the math. Those small zones are not moving 2gpm, they are moving 1.4gpm based on what you posted. So those zones are probably going to determine the water temp. What's each zones loss and how many feet of board in each zone?

    You don't need to add more board you need to add more btu/hr output utilizing the existing board foot print.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Ted89Ted89 Member Posts: 5
    radiator details

    As I posted, the two smallest load zones are 14k BTU each.  About 22' each, mostly Slant Fin 30.

  • gennadygennady Member Posts: 680

    You have to loose zoning it kills efficiency dead. Install TRVs Instead. Then install small mod con.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • ChrisChris Member Posts: 3,056
    You sure about that heat loss

    600 x 22 = 13,200 with 180 degree water. Did you do a heat loss or just measure the capable board output?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Ted89Ted89 Member Posts: 5

    Yes, did a room by room heat loss. 

    Gennady, could you please explain what you mean?

    In case someone out there thinks a heat only  modulating non-condensing boiler may be a good idea- does anyone know who makes one besides Baxi?

  • SWEISWEI Member Posts: 7,356
    Modulating, but not condensing

    in a cast iron boiler would limit you to return water temps above 130F for the vast majority of designs, though a few can tolerate 110F return water.   I'm not sure how viable a market that represents.
  • JStarJStar Member Posts: 2,668

    We installed a condensing boiler on a baseboard system yesterday. We peaked at 99.1% combustion efficiency.

    In other words...don't waste your money on reinventing the wheel. Choose a contractor, and a manufacturer that you like, and go for it.
    - Joe Starosielec
    [email protected]
  • gennadygennady Member Posts: 680
    edited June 2013

    modulating boiler has a minimum stable load. usually 20-25% of max output. if you divide minimum load into smaller loads by using zone valves, you make modulating boiler to work in on/off mode or even short cycle, and vaste a lot of fuel. If you use TRVs, you create indoor reset, and exact load from room to room. This is the most effective and comfortable heating. But you have to use VFD constant flow pump for this.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • gennadygennady Member Posts: 680

    Forgot to mention, disconnect thermostats, as well.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
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