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  1. #1
    Join Date
    Oct 2007
    Posts
    7

    Gas Boiler- Condensing versus Cast Iron?

    I am replacing an old oil boiler (converting to Nat. Gas).

    I have spoken to several compentent contractors regarding what makes sense as far as installing. I need to line chimney in the case of traditional cast iron boiler. I know the equip. costs more for condensing, but the fact I would not have to line chimney with a condensing, direct vent helps offset some of the cost..

    This question of the newer Higher Eff. equipment versus traditonal boilers seems to be a big debate between the professionals who install them.

    Besides picking the boiler brand, the type to install also brings out many varying suggestions. Any opinions would be appreciated

  2. #2
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    734

    Cast - Iron vs. Condensing

    There is actually very little intelligent debate on this issue between experienced contractors (those who put in more than a couple of boilers a year) who promote and install Mod/Con boilers. There is much speculation, but this is really of little use.


    Almost all of the technology for Modern i.e. "condensing" boilers has come from several decades of European experience. Much of the technology originated in the US but backward thinking and cheap fuel have stifled growth in our boiler industry.

    Choose any Mod/Con boiler cheerfully promoted by your local contractor and if you decide to go with 60 yr. old cast iron technology, choose the Mod/Con guy anyway. He is by definition, better informed.

    MA

  3. #3
    Join Date
    Oct 2007
    Posts
    7
    Thanks M...With $93 oil right now soon to be $100. Natty Gas will surely be ramping higher. High effiency seems to make sense.

    I see you've installed a Buderus Mod Con. Have you any experience with the Utica or Trinity condensing gas boilers? One pro I spoke to recommended a direct vent (High 80s) Slant Fin gas boiler as a way to save money on equipment and install versus condensing.

    I have to say I am leaning towards a Mod Con, but need to find someone who is comfortable with the technology and has the experience putting them in. These High Effy. unit Product Managers must be besides themselves in struggles to convince the experienced techs. to embrace the technology.

  4. #4
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    734

    Astute observation.

    I have installed many Buderus Mod/Cons and am in the process of installing the rest of the Mod/Con offerings. I have not installed the Utica but did see in a show years ago, it looks to be made by Dunkirk and old and venerable name and purveyor of private label boilers for several retailers that will remain unnamed.

    The Trinity is made by our Canadian cousins and enjoys a very loyal following hear in Minnesota. I just returned from a training school and have several bid. They are light, efficient and stainless steel that is preferred by some. They require a high head pump that is seen as a negative by others.

    This quibbling is silly considering the potential savings that are commonly 25% in real world applications. This fuel saving device coupled with an indirect (single wall) indirect water heater, is really the best thing available today.

    MA

  5. #5
    Join Date
    Oct 2007
    Posts
    7
    MA-

    I heard you guys in the Midwest do not use oil as an option much. A guy out here in NY told me today that with current oil and natty gas prices...I need a High Effy. gas boiler (condensing) to match the efficiency of a new conventional oil boiler (Cast Iron- vent through chimney)...due to the higher BTU generated by oil fired versus gas...I have hot water cast radiators in house now...

    Now I am still confused. Stay with oil? Just switch out to a new oil boiler? My original intentions were to get off the black juice...Cheaper, cleaner, etc...Maybe not?

  6. #6
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    734

    Oil vs. Natural Gas

    It is just a numbers game. If the cost per BTU British Thermal Unit is higher for NG than oil then oil is it. You have a long history in the northeast with oil and boilers. If you get your boiler serviced every year you can expect high efficiency and reliability.

    Naturally gas generally requires less maintenance to produce the same result though the jury is still out on the relatively new breed of condensing gas boilers. Here in the Midwest where oil is generally more expensive and oil technicians few and far between, our choices are few.

    Talking with a qualified heating contractor in your area who is not prejudice toward either fuel will give you the answer. Your local guy should have all the numbers in his head.

    Ask about outside reset and indirect water heaters: two things that will enhance the "operating" efficiency of any boiler.

    MA

  7. #7
    Join Date
    Nov 2000
    Posts
    1,251
    Will a condensing boiler work (that is to say, will it condense) if you have radiators that give you 150 to 160 degree return water temp?
    Just asking.
    "You do not merely want to be considered just the best of the best. You want to be considered the only ones who do what you do.".... Jerry Garcia
    "You just have to decide if you're a Tigger or an Eeyore,..I think you know where I stand on the great Tigger/Eeyore debate." Prof. Randy Pausch

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    With a mod /condensing boiler. You should also use OD reset.
    Then the boiler only heats the water as hot as needed to heat your house that day,
    Why heat you CI rads to 150, if they only need to be 130.
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  9. #9
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    734

    Nearly all Mod/Cons have outdoor reset built-in

    This is one of the great advantages of Mod/Cons; another is that they are more efficient at burning gas than conventional gas boilers. They start above 90% AFUE - naturally aspirated boilers are 86% efficient and below by definition. Some Mod-Con boiler claim 98% thermal efficiency and real operation efficiency - AFUE - is enhanced by outdoor reset as this boiler will operate in a full range of space heating water temperatures.

    Re-set matches boiler water temperature to outdoor air temperature on a scale. In temperate weather you may only need 80F water to heat your home and only during design conditions - a couple of days a year - will you need the 160F your system may have been designed for. Many of my old homes with cast iron radiators have been upgraded with insulation and new window etc. These homes are heated with 100-year-old radiators that never get above 140F.

    Conventional low efficiency boilers - 86% and below - will also benefit from outdoor re-set but to a lesser degree, because conventional boilers will condense when return water temperatures reach 130F or so. Outdoor reset will protect the boiler from slightly acidic condensate that is bad for cast-iron conventional boilers.

    The last and perhaps most important advantage to outdoor reset controls whether applied to conventional or condensing boilers is that a more constant flow on warm water is delivered to the space. This eliminated cold drafts between the hard-on, hard-off cycles of old.

    MA

  10. #10
    Join Date
    Oct 2007
    Posts
    7
    MA-

    Just replaced an old 150,000 oil boiler beast with a Munchkin 80 with outdoor reset (nat. gas). The way this unit drives my old CI radiators is simply amazing. My house has never been so warm and comfortable.

    Your posts in this thread are spot on. I was lucky enough to find a pro in my area that understands and has embraced the technology. Why there are not not more of these Mod/Cons installed on the east coast is beyond me. Even the local gas company is clueless on the subject.

    Thanks

    Quote Originally Posted by BadgerBoiler MN View Post
    This is one of the great advantages of Mod/Cons; another is that they are more efficient at burning gas than conventional gas boilers. They start above 90% AFUE - naturally aspirated boilers are 86% efficient and below by definition. Some Mod-Con boiler claim 98% thermal efficiency and real operation efficiency - AFUE - is enhanced by outdoor reset as this boiler will operate in a full range of space heating water temperatures.

    Re-set matches boiler water temperature to outdoor air temperature on a scale. In temperate weather you may only need 80F water to heat your home and only during design conditions - a couple of days a year - will you need the 160F your system may have been designed for. Many of my old homes with cast iron radiators have been upgraded with insulation and new window etc. These homes are heated with 100-year-old radiators that never get above 140F.

    Conventional low efficiency boilers - 86% and below - will also benefit from outdoor re-set but to a lesser degree, because conventional boilers will condense when return water temperatures reach 130F or so. Outdoor reset will protect the boiler from slightly acidic condensate that is bad for cast-iron conventional boilers.

    The last and perhaps most important advantage to outdoor reset controls whether applied to conventional or condensing boilers is that a more constant flow on warm water is delivered to the space. This eliminated cold drafts between the hard-on, hard-off cycles of old.

    MA

  11. #11
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    734
    It only took 20 years, but good on ya!

    MA

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