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  1. #1
    Join Date
    Mar 2020
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    Post Oil to Gas Conversion + Central AC install

    Thank you in advance for any guidance you can provide!

    I'm limited on details (i.e. load calcs), but please let me know what other info I can provide. We are looking to convert from Oil to Gas, then add Central AC. In the next few years, we will be adding a bedroom and full bath to the attic, so we are planning for that in our heating/cooling design. The property is in Massachusetts.

    House:
    Build = 1936 (Colonial)
    Siding = Vinyl
    Walls = Plaster (no insulation)
    Basement = 500 sq ft finished (electric heater) & 550 sq ft unfinished
    1st Fl = 1,088 sq ft - 1 bedroom, 1/2 bathroom
    2nd Fl = 972 sq ft - 3 bedroom, 1.5 bathroom
    Attic = 936 sq ft - unfinished, but will finish in the near future

    Current Heating = Oil, forced hot water, indirect tank
    Current AC = window unit

    We've had a few contractors in to bid on this, with recommendations that have varied. All have recommended converting to gas and a central AC system, but a few recommended utilizing a heat pump (no electric coil) within the central AC (gas boiler would still be installed). Most have recommended replacing the old indirect tank with a new one, only one recommended tankless.

    For heating & cooling the attic, the recommendations range from a dedicated heat pump / mini split, to running new pipes up for the forced hot water and a damper for the new AC vent for the attic. As an aside, I have a plumber replacing every single pipe in the house, so I don't think adding baseboards / radiators in the attic would be as significant if he would not there already.

    Thoughts on the overall design approach? Which direction would you go? If there are additional details I can provide, please let me know.

    I also have all the specs on the boilers & A/C system if it would be helpful to post those.

  2. #2
    Join Date
    Jan 2010
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    Did you consider insulating the walls to tighten up the envelope ?
    Windows ?

  3. #3
    Join Date
    Aug 2002
    Location
    Southold, NY
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    NG or LP?

    Also keep in mind new gas service is being closed down all over.

  4. #4
    Join Date
    Oct 2011
    Location
    Culver, Oregon (Central OR)
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    Has anyone offered dual fuel?

  5. #5
    Join Date
    Mar 2020
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    Thread Starter
    No dual fuel recommendations from the contractors, gas would be NG. All windows in the house are Harvey windows, ~ 5yrs old.

    For the walls, Mass Save recommended blow-in, but after doing some research, it seemed pretty consistent that folks recommended not adding blow-in insulation behind plaster walls...settling, mildew, etc. However, I've read about "Blow In Blanket" and that supposedly doesn't have the same issues with plaster walls. Thoughts?

  6. #6
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Is there NG in the house already and is the line large enough?

  7. #7
    Join Date
    Oct 2011
    Location
    Culver, Oregon (Central OR)
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    Quote Originally Posted by Sparg93 View Post
    No dual fuel recommendations from the contractors, gas would be NG. All windows in the house are Harvey windows, ~ 5yrs old.

    For the walls, Mass Save recommended blow-in, but after doing some research, it seemed pretty consistent that folks recommended not adding blow-in insulation behind plaster walls...settling, mildew, etc. However, I've read about "Blow In Blanket" and that supposedly doesn't have the same issues with plaster walls. Thoughts?
    Ask them.

  8. #8
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    Mar 2020
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Is there NG in the house already and is the line large enough?
    There is existing NG, but current line going into house is undersized, so it will be replaced.

    Thoughts on if a heat pump is the way to go? Would you also dedicate a mini split/heat pump in the attic or plumb radiant heat up and then dampen the central AC?

    Also, all have recommended modulating boilers, with the lower range kicking in around 20 - 30k BTU, depending on boiler. The max have been around 115 - 150k BTU. Would you recommend keeping the indirect or going with tankless?

  9. #9
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Be advised gas companies are restricting upgrades or new hookups all over the NE. L I is currently fully restricted. NO new gas service, NO increase in supply lines.

    As far as Mod cons a full heat load loss must be performed. The old radiators were rated for 180F water, no advantage to high efficiency equipment when ran over 140F. All those radiators may have to be replaced or modified.

    As far as A/C Heat pumps Yes. 1 system for each floor.

  10. #10
    Join Date
    Mar 2020
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Be advised gas companies are restricting upgrades or new hookups all over the NE. L I is currently fully restricted. NO new gas service, NO increase in supply lines.

    As far as Mod cons a full heat load loss must be performed. The old radiators were rated for 180F water, no advantage to high efficiency equipment when ran over 140F. All those radiators may have to be replaced or modified.

    As far as A/C Heat pumps Yes. 1 system for each floor.
    Thanks Pecmsg - I'm not familiar with the above. What would I replace the hot water radiators with and/or modify? I'm guessing the investment would be significant to complete...thoughts on payback time?

    There's also the option to go combined forced hot air + AC, even adding a hot water coil.

    I'm down to the studs in my house so I have a few options, but with recommendations coming from every corner, I'm having a hard time weeding through it all. Recommendations?

  11. #11
    Join Date
    Aug 2002
    Location
    Southold, NY
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    With a unlimited budget...………

    In floor radiant heat to take the chill off the floors.
    Heat pumps with Hot Water coils designed for lower water temperatures. (140F Max)

    ALL of this is Highly dependent on the installing contractor and there design team. Properly designed and installed and you'll have a comfortable home!

  12. #12
    Join Date
    Jan 2012
    Location
    Broomall, PA
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    You need a proper design, based off a proper heat loss. That heat loss should consider all new envelope improvements-doors, windows, insulation, etc.
    Ideal is all radiant for heat, adding AC w/heat pump for back up, and shoulder seasons. This is what I have, and I never use the heat pump.
    For a quick load calc, what's your city/state/zip, how many gallons of heating oil did you use last year, and what's your current equipment?
    Proper sizing is most important, and a qualified competent tech would know this. Oversizing is wasteful, inefficient and shortens equipment life.
    You could also look into products from Energy Kinetics.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

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