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Indirect vs. tankless coil energy savings

EricD Member Posts: 4
I am getting ready to replace my ancient Columbia oil-fired boiler with a new system, and have quotes for a Weil-McLain WTGO3 with a domestic hot water coil and a Buderus G115WS/4 paired with a Buderus ST160 indirect tank.  I know that the Buderus will be a little more efficient, but I am having a difficult time finding hard numbers on annual fuel savings of indirect systems versus ones with tankless coils.  Calculating payback periods is, therefore, almost impossible.

Can anyone give real-world guidance on the percentage annual fuel savings of one type over the other?  As for climate, I am in Maryland.


  • Ironman
    Ironman Member Posts: 7,119
    No Comparison

    Go with the Buderus. It will not only be more efficient, but it's much easier to clean and maintain. I would highly recommend that you add the 2107 logamatic control. You'll see at least a 30% fuel savings with it.

    As with any install, the contractor is the key. A good one can take an average system and make it perform well, and a bad one can turn the best system into a nightmare.

    Where are you at in MD?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EricD
    EricD Member Posts: 4
    How much more efficient?

    Thanks for the reply.  I am near Columbia, MD.

    Since the Buderus water heater warranty I saw states that the unit has to be "maintained and repaired by a heating contractor whose principal occupation is the sale and installation of plumbing, heating and/or, air conditioning equipment", I suppose how easy it will be to clean is not my concern.

    Here is my problem.  Everyone seems to agree that the Buderus with the indirect is more efficient, but by the time you add in the Logamatic controller, it is $4000 more than the Weil-McLain, so I need to get an idea for how much more efficient to calculate a payback.  Is the Buderus really THAT much more efficient than a brand-new WM?
  • meplumber
    meplumber Member Posts: 678
    The short answer is yes.

    We do not discuss pricing in this forum.  However, you can expect a clean 30% fuel saving by using the Buderus with 2107 and an indirect.  Assuming that you currently use 1,000 gallons a year (normal with a tankless coil up here in Maine) that would be 300 gallons a year.  At current fuel prices, that adds up fast. 

    It is impossible for us to give you a hard number, because each structure and application is different.  Trust the years of hard earned experience by the members of this board and go with the indirect.  If you can afford it, add the 2107 control.

    The biggest thing to consider is that the casting of the Buderus is capable of operating at lower water temperatures.  The 2107 control is designed specifically for the Buderus, by Buderus.  It controls your heating circulator, the burner, and the indirect tank.  It is the most effective way of squeezing the most out of every gallon of oil with that equipment.

    I agree with Ironman, a top notch installer is the key to everything.

    Good Luck.
  • meplumber
    meplumber Member Posts: 678
    edited June 2011
    Duplicate Post.

  • meplumber
    meplumber Member Posts: 678
    edited June 2011
    Triplicate Post.

  • EricD
    EricD Member Posts: 4
    Now THAT'S the info I needed

    Yes, I know you don't discuss pricing, and that's not what I was looking for.  I can "afford" to spend whatever is justified.   I just needed some info to allow me to make some payback calculations, and it now looks like I have that. 

    Here is my thinking.  I am currently averaging about 1100 gallons per year with the relic in the basement.  I figure upgrading to the new boiler with the tankless coil would save at least 25%, which, at Department of Energy predicted prices for 2012, works out to a 5.3 year payback.  Going with the Buderus G115WS, indirect tank, and Logamatic, your prediction based on your experience is another 30% on top of that.  If I go a little more conservative, and figure only 25% over the WM with tankless, I get a payback that is actually SHORTER (5.1 years) for the more expensive system.  Even if the numbers are off a little, it still looks like it is justified to spend more for the more efficient system.

    If, however, I was looking at 30% reduction in consumption over my ancient relic, compared with 25% with a new boiler with a tankless coil, then the economics simply aren't there.

    Thanks for the information!
  • Ironman
    Ironman Member Posts: 7,119

    As pointed out, we're not allowed to discuss pricing. But the variation may have more to do with the contractors. One may be including things that the other is not. It always cost more to do the job right. I'm not saying the low bidder wouldn't, but the old adage applies:"You get what you pay for".

    If you're not settled with your current bids, I would recommend Dan Foley of Foley Mechanical in Lorton, VA. He's under the "Find a Contractor" tab above. I'm not sure if they go as far as Columbia, but it's worth a call.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EricD
    EricD Member Posts: 4
    Oh, wow

    Walked away while composing a response, got the "log in again", and it lost my multi-paragraph response.  Gotta fix that "time out and lose it" problem.  Not going to type all that over again.  So 1990s web technology.

    It was the same contractor gave me multiple proposals
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    It always cost more to do the job right.

    I do not know about the heating business, but in the software design business, where I used to work, this is not necessarily true. Novices right out of school tend to come up with very interesting designs that cost a lot to implement, are difficult to modify, require more memory, and more processing power than others who have been in the field for a while. The "old timers" think longer before coming up with the design, and these designs end up being simpler, quicker to implement, easier to test, and require fewer resources. Now being an "old timer" is not a guarantee. Some people have 20 years experience, and others have 6 months experience 40 times. It is not the same. You have to have learned something from your experience. But quite often doing the job right costs less, especially if the cost over the product's lifetime is the criterion.
  • Mac_R
    Mac_R Member Posts: 117

    I install primarily Buderus G115 with the 2107 Logamatic control.  I have seen savings from 45% all the way to 70%.  The key is to use the BFU room temp sensor and run the circulator on constant run.  The BFU will set the system to room reset not just outdoor reset.  It will take into account people in the room as well as if you are cooking.  If the oven is on you don't need the same temp in the system than if it were off.  I find it to be much more comfortable than just using outdoor reset alone.  Another big thing is what kind of heat do you have?  Is it baseboard, radiant, or cast iron radiators?  Each one of these require different water temps and the BFU will compensate for each.

    Just for an example.  I put a new system in my Aunt's home last September.  She had a Bhurnham boiler with a hot water coil.  I replaced that system with a Buderus G115WS/3 with the Logamatic 2107 and a S120 Indirect tank.  On average she would burn about 200 gallons of fuel per month during the winter.  Oct- Feb.  Last December she used 60 gallons.  that is a 70% savings.  The home is more evenly heated and she no longer runs out of hot water.  Love the Buderus and the Logamatic.  In my opinion there is no better system. 
  • Steamhead
    Steamhead Member Posts: 15,994
    Columbia is closer to Baltimore than DC

    and that's where we are- give us a call!
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • carl_nh
    carl_nh Member Posts: 27
    Savings Verified - Buderus

    I installed the Buderus G125-21BE (Blue Flame 90.7% Eff) Oil Boiler in Feb 09 with ST160 DHW tank to heat our 2800SF cape in NH. Heat Loss 65-75K BTU.

    The G125 series comes with the Logimatic 2107, Tiger Loop, Preheater for oil, and burns blue - very clean! We used 900 gal per year in the previous two years and since installation we are using 500 gallons annually.

    Cost of the G125BE series is $2K more than a G115 BUT it has the Logimatic, Tiger loop and blue flame burner technology INCLUDED. This every thing else was equal - installation, plumbing, three speed Grundfos circulators, down to the nickel.

    Then the Fed tax credit for 90% + oil boilers for $1500 was the icing on the cake plus we are saving $1200+ at $3.30 gal oil per year.

    So when I added it up $1500 tax credit + $1200 annually = a ROI of 6 years for our COMPLETE installation.
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