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Thread: Boiler - Oil vs Propane

  1. #1
    DIY Junior Member frank in ohio's Avatar
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    Default Boiler - Oil vs Propane

    My oil fired boiler is 30+ years old, it still works but probably needs some work, and with the cost of fuel oil being close to 4 bucks a gallon, I was considering replacing it with a propane fired boiler. Those are the only choices that I have. Some contractors have told me to avoid propane at all costs, something about the BTUs per gallon as compared to fuel oil. Others have said that with the efficiency of todays propane boilers, it is probably a wash. Me, I haven't a clue. Would like to hear some professional opinions. I have a simple ranch house with baseboard heat from the boiler, two zones.

    thanks
    frank

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Don't know the energy equivalent between propane and fuel oil, but I'm sure you can find it with a search. then, you can compare the cost per BTU. A gas-fired boiler is much easier to modulate, and that may make it much more efficient than a fixed output oil burner. This would let the boiler match the exact heat need fo the building, and not cycle as much. But, it will cost more in startup, since you'll need the tank and a modulating boiler is more expensive than a fixed output version. Many use direct vent and are closed combustion, so this helps in efficiency as well since it isn't drawing combustion air through the cracks in the house (there's less to reheat, and the house would feel less drafty). Some utility companies are offering rebates for efficiency (especially if you had natural gas, but maybe still for propane). The tax credit has expired (I think). So, lots of things to investigate. A 30+ year old boiler is almost certainly much oversized unless you've added on lots to the building, so first thing is a good analysis of the building. You can get an idea by comparing oil use to the heating degree day values for your location. You'll probably be surprised at how low that is. For efficiency, the worst thing is an oversized boiler!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    "There's no more convenient heat than electric heat — until you have to pay the bill at the end of each month," he said. "Firewood's a good alternative for me. I have an old wood stove, and I enjoy chopping firewood as physical exercise. That might not be appropriate for others, so they might consider wood pellets as an alternative. If you decide to go with wood pellets or shelled corn, you'll need a pellet stove or boiler. So you'll need to include the cost of purchasing the system in your calculations as well."

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    DIY Junior Member dapoppa's Avatar
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    In rounded numbers, a gallon of LP will give 90,000 btus. A gallon of #2 will give 140,000 btus. Do the math to find the better buy.

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    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by dapoppa View Post
    In rounded numbers, a gallon of LP will give 90,000 btus. A gallon of #2 will give 140,000 btus. Do the math to find the better buy.
    Here on Long Island, NY, a gallon of #2 heating oil last delivery in May, was about $3.80. My last delivery of propane that I use for my gas log fireplace and hot tub heater was much more than that per gallon, over 4 bucks per. don't have the delivery ticket with me where I am right now, but i sure would not want to heat my home with propane here. Natural gas main is about 1/4 mile from my block, so that also is out of the question for me
    I am definitely not a pro plumber, but I am a pro crastinator

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    In the Trades Tom Sawyer's Avatar
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    Go here http://www.nora-oilheat.org/site20/index.mv?screen=home

    Go half way down the page until you see the NORA calculator

    Download the software, it has no viruses and run it. You will need to get local fuel prices and ask your oil company for your K factor. Then you can compare any equipment against anything else. What you will find is that oil is cheaper to operate gallon for gallon
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  7. #7
    In the trades Dana's Avatar
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    Unless the thing is completely toast, replacing the boiler isn't a very cost-effective efficiency improvement. You can probably get double-digit improvements out of a better controller such as the Intellicon HW+ (worth doing, if the boiler has another 5-10 years in it, which it might), but dropping money into a condensing propane or high efficiency oil boiler you're looking at a 25-30% savings, best case.

    A more cost effective solution is to keep the boiler (but adding an intellicon) but to add an R410A refrigerant mini-split heat pump with at least 2-ton (24,000BTU/hr) nominal heating capacity which would cut down your heating cost substantially if used as the primary heat source, using the boiler only as the backup during the bitterest weather. In an OH climate you can count on getting an average coefficient of performance (COP) of 2.5, and maybe close to 3.0. At 2.5, it means for every kilowatt-hour (kwh) of electricity expended, you get 2.5 kilowatt hours of heat put into the house.

    The economics of it work this way:

    1kwh=3412 BTU, so for every kwh used by the heat pump you get 2.5x 3412 = 8530 BTU into the house. For every 10kwh you get 85,300 BTUs into the house, which is about what you'd get out of one gallon of propane in a 94% AFUE condensing boiler (assuming you have enough baseboard to run at condensing temps most of the time.) If you're paying 12 cents/kwh, that's roughly equivalent to $1.20/gallon propane. Even at 20cents/kwh (probably way more than you're paying in OH) that would be $2 propane.

    Priced propane lately?

    Assuming your 30year old boiler is running 75% efficiency or better (which it probably can, with an Intellicon HW+ controller), call it 85%, every gallon of oil delivers 0.85 x 140000= 119,000 BTUs to the house. With a mini-split heat pump that would take 119,000/8530= 14kwh. At 12 cent/kwh running the heat pump is equivalent to $1.68/gallon oil in your boiler, at 20 cent electricity it's like $280 oil.

    In a state of the art 90% Buderus you're looking at 126000 BTU/gallon, which is closer to 15 kwh in the mini split, so at 12 cent electricity it's like $1.80 oil in the Buderus, a 20 cents it's like $3 oil in a Buderus.

    A 24,000BTU single-head mini split is under $5K. Add about $1200-1500 per head for the interior units for multi-splits. You can probably even put in a 36,000 BTU multi-split for less than the cost of state of the art Buderus, and it would probably cost half as much to run. There are multiple vendors (Fujistu, Mitsubishi, Daikin, Sanyo, LG, etc etc.), but finding one with good local distribution & support is a good idea. They're practically (but not completely) idiot-proof to install, but there's always a better idiot to be found, if you're really looking. You want to get something with an HSPF (heating season performance factor) of at least 9.5-9. I've been sticking with the short list compiled by a pacific northwest monitoring program, but there are others out there.

    During the shoulder seasons they'd run a COP of 3 or better, but below 10F they're only about 2-ish, at which point running the oil boiler isn't dramatically more expensive as the backup. Don't use set-backs with them- they run more efficiently if you "set and forget". Set the T-stats for the boiler a couple degrees below that of the mini-split and you're golden- it'll only fire up when the mini-split can't keep up, which will be mostly during the coldest 5% of winter hours.

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