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.

I am Confused

Jason_13 Member Posts: 304
I read a lot of posts here about the need for smaller mod/con boilers.
The ALP080 has a 5:1 turn down from 80k to 16k. To drop the low side maybe utilizing a 10:1 turn down makes sense. The upper side does not make all the sense to me. If I need 40K due to my heat loss I can install the ALP080 and limit the firing rate to 40K and will now allow an input from 40K to 16K.
An alternative is to make a smaller boiler that may go from 50K down. A smaller heat exchanger. Is it not more efficient to turn down the 80K which means the ratio of fire side heat exchanger to input is greater and a higher efficiency.
I believe if they would control the circulator or we can do that in the field. If the boiler is limited to 40K we can just use a smaller circulator than required on an 80K.
BTW, that new zone control that limits the input according to the heat loss of the zone is really cool.


  • Jamie Hall
    Jamie Hall Member Posts: 22,050
    Most combustion devices -- and a boiler is no exception -- have a design firing range. A 5 to 1 turn down is, nowadays, somewhat expected. A 10 to 1 turn down range is achievable, but trickier. But... the real thing is that within that range, the efficiency will vary. Depending on the details of the boiler design and installation, it will probably be best in the upper third of the turn down range, and drop -- perhaps not drastically, but drop -- as the firing rate drops. The shape of the efficiency/firing rate curve is heavily influenced by the boiler and firing design. Only very careful testing over the full firing range will reveal where the peak efficiency in a particular installation will be. The installed efficiency will also vary with the water temperatures and temperature distribution in the boiler.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Rich_49
    Rich_49 Member Posts: 2,762
    You should like this jamie .

    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
    Mark Eatherton
  • SWEI
    SWEI Member Posts: 7,356
    Smaller boiler = lower materials cost, lower shipping costs, lower warehousing costs. At some point, it will make sense.
    Mark Eathertonjonny88RobG