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New boiler Advice

Fedpro
Fedpro Member Posts: 8
My Burnham v74 has started leaking and needs to be replaced.  My house is about 2400 square feet with 156 feet of finned tubular radiators and I have a design heat loss of 59322 BTU/hr.  I'm considering a Burnham MPO or a Buderus G115.  But I seem to be getting conflicting quotes.  One is for a Buderus G115WS/4, another company quoted me on a Buderus G115WS/5 and the Burnham was for a Burnham MPO 147.  I'm not sure what size I really need - any help would be appreciated.

Comments

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    boiler size

    Since I am a homeowner, not a professional, I cannot tell you what size you need either.



    I can say one thing, though. It is extremely easy to figure out the boiler size needed when you know the heat loss of your building. Each contractor should have performed a heat loss calculation to determine the heat loss of your building and from that to determine the size boiler you need.. Do not accept a contractor like my former one who just walked around two sides of my house and counted his paces. Also, do not accept a contractor who looked at the plate of your existing boiler and proposes one equal or larger than what you have. This standard will rule out a lot of incompetent contractors.



    Only if you have more than one contractor who did a real heat loss calculation will you have a problem. The big issue is to pick the best contractor, because in the long run, the performance of your system will depend more upon the ability of the contractor than anything else.



    Once you have selected a contractor, discuss the pros and cons of a modulating-condensing boiler. They cost more to install, and their maintenence is more too, but their fuel costs are considerably less provided you get low enough return water temperatures. I have radiant in slab heat downstairs that has low enough return water temperature. My upstairs is fin-tube, and I deliberately installed more than I would normally have in order to get lower return temperatures.
  • Al Letellier_21
    Al Letellier_21 Member Posts: 402
    new boiler

    Assuming your numbers are correct, you are way over radiated as 156 feet will give you around 96,000 BTU's so you have to be sure of your numbers. You didn't mention what you are doing for domestic hot water, but assuming you are going to use an indirect, the Buderus would be my choice. Make sure the bids you get include the heat loss calculations.
  • Fedpro
    Fedpro Member Posts: 8
    New Boiler

    Al, we have a tankless coil now, but the new system will have a 40 gal. Super Stor indirect tank or a Buderus ST200 50 gal indirect water heater.   The radiator measurements were checked twice and are correct - 156 feet.  House is a split level with a 700 foot addition of two rooms and a bath over an unheated two car garage and the basement is finished and heated.  When we finished the basement 15 years ago,  an audit was done and we were told we needed the present size boiler which is the Burnham PV74.  I'm leaning toward a Buderus also, just don't know if it should be the 115/4 or 5.
  • meplumber
    meplumber Member Posts: 678
    Great chance for outdoor reset.

    I agree with Al.  You are way over radiated.  You could get by with lower water temperatures to the radiation.



    With that much over radiation, it would be a great chance to take advantage of the outdoor reset capabilities on the 2107 Buderus control.  This would save quite a bit of fuel by not requiring the boiler to run with such a high water temperature.  It has a built in boiler protection temperature by not allowing the circulators to come on if the boiler temp is 104 deg F. 



    The key is that it has to be wired and setup correctly.  Be picky with your contractor selection.  It is more important than the boiler selection.



    Good Luck.
  • Fedpro
    Fedpro Member Posts: 8
    Outdoor reset

    Ok, I have actually been considering the 2107 Logamatic control, but which boiler, the 115/4 or 115/5?
  • meplumber
    meplumber Member Posts: 678
    The 115/4 is more than enough.

    Assuming that your numbers are correct the 4 is more than enough.



    You might even consider the 115/3.  Have the prospective contractor do a true heat loss on the structure.  Then use that to size the boiler.  Have him take into consideration the DHW tank.  Up here in Maine we have such high heat loses due to our -10 or greater design temps that DHW isn't an issue.



    It may be if you are in a warmer climate.



    Good Luck
  • billtwocase
    billtwocase Member Posts: 2,385
    just a thought

    any warranty left on the old boiler?
This discussion has been closed.