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Replacing Oil Boiler

drake | Posted in General Questions on

I live in Halifax NS, and am looking to replace a 19-yr old oil-fired boiler with tankless coil for DHW. My 2 story home +/- 2600 sf is heated via radiant in-slab on 1st floor, hot water baseboard on 2nd floor.

Ideally I would like to use an air to water heat pump, but understand the higher temps required for hot water baseboard are a problem for air to water heat pumps. I would like to stay away from fossil fuels for the replacement system – no oil or propane. 

Any ideas for a replacement system? Greatly appreciated, thank you.

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  1. paul_wiedefeld | | #1

    This is a fine application for an air-to-water heat pump, but you're right, some creativity will be needed for the baseboard.

    A few options, all of which can be combined with one another to handle the baseboard:
    1. Determine the actual heat loss of the rooms with baseboard. You want to find out the BTUs needed divided by the linear feet of baseboard for those rooms, then compare that to the output/linear foot of the baseboard at temperatures around 120F. If you're extremely lucky, the baseboard might work as is!
    2. Try targeted heat loss reductions for the rooms with baseboard to get them in line with the outputs provided by the existing baseboard.
    3. Increase the output of the baseboard by replacement and/or addition. You can install higher output baseboard or an alternative, like a panel radiator. Or if there's space, more of the same.
    4. Use a different heat source to increase the water temperature to the temperatures needed for the coldest days. You have several options here:
    a. you can keep the existing oil boiler. Depending on the baseboard floors heat loss,
    you might only need higher temperatures for a fraction of the year, so the carbon
    intensity of the boiler would be low. It would also function as a backup in case
    something happens to the heat pump.
    b. you can add an electric boiler. It's expensive to run but cheap to install. Same
    concept as the oil boiler: ideally, the heat loss allows it to only run a small
    percentage of the year.
    c. You can add a water-to-water heat pump which can reach a higher temperature
    than the air-to-water can. Usually this means using a different refrigerant. Nordic is
    a Canadian manufacturer that sells these.
    d. Somewhat similar to b., you can install backup electric heat, but in the rooms
    themselves. If it's just a few rooms, this might be easier than installing an electric
    boiler. It also provides a redundant system - you'll be fine if a pump fails, etc.
    5. You can also consider an air-to-air system: perhaps, you'll want AC in the future and this could justify running ductwork. From there, it's easy to use a heat pump.

    As for the DHW, that’s easy. Integrated hot water with an indirect water heater, or separate heat pump or resistance tank.

    Here's a great resource:

  2. drake | | #2

    Thank you Paul, very helpful.

  3. walta100 | | #3

    Do you really want to be the pioneer in the ATWHP (air to water heat pump) many pioneers get slaughtered.

    New equipment is rare is hen’s teeth. Priced like diamonds. Manufactures come and go like the wind. Experienced installers are non-existent. Local replacement parts stock is a joke.

    The safe bet is to buy 4X the number of solar panels and a simple electric boiler.


  4. iwatson | | #4

    Hey Drake,

    I'm also in Halifax and am looking to go air-to-water, so I'll be interested in your experience. I currently have oil-fired cast iron rads.

    For DWH, I ran all the numbers and came to the conclusion that a simple electric resistance tank was the way to go. Heat pump for DWH just isn't worth the cost or complexity. Electric tankless seems nice for space savings. If you have the space for a tanked system, the Giant 3-coil systems qualify for a big EfficiencyNS rebate. I've been very happy with mine.

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