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Replacing oil boiler - mini split or combi boiler

barkroy Member Posts: 2
Hello. We have a small 1100ish sqft single level ranch style home near Phoenicia, NY. Current heating is baseboard powered by a Peerless EC-03 boiler which also provides hotwater for the home. There is about 70' of baseboard element throughout the house. The boiler is at least 20 yo (preventive replacement), oil prices are insane (don't think system is especially efficient) not to mention 2 tanks inside (would love that space). Have been considering mini-split system but a bit turned off by the price tag plus ancillary cost (potential new breaker, new backup generator, need to work out hot water) as well as the size of the wall units (smaller home/low ceilings) vs the additional cost for ceiling cassettes. Now strongly considering a combination boiler. The combi boiler looks like it will cover our needs, give higher efficiency than current, oil tanks go away and no ancillary electric costs. Also first quote on mini split suggested we keep the boiler in place as backup to mini split for the cold sub zero winter days/nights (another mark against mini split)
No idea about actual efficiency and more importantly reliability of the combi boiler. Any thoughts, suggestions greatly appreciated.


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,906
    edited August 2022
    @barkroy Does this home have AC? If not, do you want AC?

    How many gallons of oil did you use last year?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
    Actually, There are no free lunches. The Combi Boiler will get you where you want to be if new equipment is necessary. The key word is NECESSARY. I have worked on Peerless oil fired boilers that were 50 years old and still operating properly. The oil burner is probably as efficient as any new boiler might have. Havr you had the burner properly maintained? A good clean heat exchanger, along with a properly tuned Flame retention oil burner like the Beckett AF or AFG can be very efficient. The price of natural gas and propane are not far behind the price increases of fuel oil. Add the cost of the new boiler installation, you may find the 20 years of savings in lower operating cost might not equal the price of the new equipment.

    On the other hand, if the boiler failed and you must replace it, then the additional coat of high efficiency equipment is well worth the investment. The difference between a $10,000.00 new boiler and a $13,000.00 new boiler that will lower your operating cost, will make sense because only $3,000.00 needs to be considered, since $10,000.00 is being spent anyway! And if $3,000.00 saves $300.00 to $500,00 in annual operating cost then the savings will offset the additional before the new equipment becomes old equipment.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    EBEBRATT-Ed Member Posts: 15,767
    Unless you oil tanks or boiler is failing, I would keep what you have if you're thinking about a combi with propane.

    If you have natural gas a combi might make more sense. If you in a cold climate and have had baseboard hw I doubt you would be happy with a mini split
  • hot_rod
    hot_rod Member Posts: 22,396
    How do the fuel costs comp[are in your area? LP prices vary quite a but from state to state.
    This site give you a cost comparison once you know local costs, plug it in.

    The EIA site has the history of the fuel costs for most areas going back 20 years or more to see past cycles.


    A heat load calc on your home as it stands would determine the loads to see how the baseboard and loads match. www.slantfin.com has a free load calculator.

    IF you go with a mod con you could run a variable temperature system and increase efficiency of the condensing boiler. 70' of baseboard running 180 would get you around 38,000 btu/hr. I'll bet your heatload is less than that for 1100 sq. ft. So you could run lower temperatures, outdoor reset. Crunch some numbers.
    An 80 or 110 combi might be ideal if you do want to switch fuels. They can easily convert from LP to NG is gas becomes available.

    A mini-split for cooling and shoulder season heating, plug the electric costs into that calculator also. If you like the comfort of hydronic baseboard, the mini-split may disappoint for heating.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • vtfarmer
    vtfarmer Member Posts: 101
    edited August 2022
    FWIW, I went from living in homes in upstate NY and VT with oil and wood fired HW BB and cast iron radiators, respectively, to a home in the mountains of west central Virginia heated by a pair of heat pumps plus a cassette style mini split and find that I need to keep the thermostats at 71-73 to feel as comfortable as I did with the hydronic systems set at 66-68 (in much colder climates).

    The other point I'll make as a DIYer is that mini splits are a PITA to own long term: the indoor units get filthy with mold, dog hair, and dust and are the devil to clean and the whole system is hard to get parts for. Plus the drain got plugged on the indoor cassette once and it flooded the room out - if one of the central systems did that it would have leaked harmlessly into the basement floor drain.
  • pecmsg
    pecmsg Member Posts: 4,916
    I don't see you recouping the money wasted on a high efficiency combo! There only High Efficiency when the supply water is below 140°F. Your system was designed for 180°F supply water so your back in the mid 80's #'s.

    1st Get an accurate heat load calc done. Slant Fin has one you can do.
    Now look at where the envelope can be tightened, insulation, windows, doors. Those you'll get a return on investment. Enter the #'s again and see how much smaller you can go.

    If the existing Peerless EC-03 boiler is oversized as I suspect, getting a smaller oil fired will save a lot.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    I'd think your best bet would be an EK.
    It's the most efficient, will give you all the domestic hot water you need, and most models can be converted to nat gas or propane.
    2 oil tanks for 1100 sq ft sounds like a lot, unless it's hard to get heating oil deliveries in your area or you just like to fill them both at once and be done with it for the season.
    Oil prices did spike and have come down a lot of their highs. Almost none of my customers even got a delivery at the high prices at the end of last season.
    If you want to add the mini splits for AC and shoulder heating season, that might be a good idea too.

    There was an error rendering this rich post.

  • Nsherman2006
    Nsherman2006 Member Posts: 25
    What about having the boiler serviced to ensure it’s running optimally, and installing mini splits to shoulder the majority of the heating/cooling load. You should be able to remove one oil tank if you do so.

    I have a 1500sf ranch in CT and I installed solar with a new roof, so I left the existing boiler in place but added mini splits and a heat pump water heater to move the majority of the heating to electric. I have the comfort of baseboard heating in the winter when needed, and the added efficiency of the heat pumps in moderate temperatures 
  • barkroy
    barkroy Member Posts: 2
    Wow! thanks everyone for all the feedback, alot to chew on here...and definitely giving this a rethink. Going to do the slant/fin load calc and see if I can get a bit more data driven about efficiency gains and amortization of new equip. We do not currently have a/c would be nice for the 3-10 days it gets tropical in the Catskills but generally it cools enough at night. Also should have mentioned that we have a woodstove which we use to do a fair share of the winter heating, some of the back rooms hover in the low 60's but makes for a good nights sleep. We typically get the 2 tanks filled annually so go through about 500 gals/year. I am taking the "necessary" to heart and leaning towards letting the Peerless runs it's life span, it is arguably in good shape despite it's years, could use a cleaning/servicing. thinking to explore slower approach to DIY a couple ceiling mount mini splits for shoulder and the occasional a/c + resale/investment value and when the Peerless gives it's final chug look to combi replacement or what a data driven analysis might prescribe.
    Again, huge thanks to this community, such an incredible and responsive resource. Finally if anyone can share any oil boiler service rec's in the Catskills.