Heating workshop: Boiler vs mini-split vs ???

paulm81 Posted By paulm81, Jan 28, 2013 at 1:51 PM

  1. paulm81

    paulm81
    New Member

    Feb 15, 2012
    29
    13
    Loc:
    Lucknow Ontario
    I built a new workshop over the last several months and am now considering options to heat it. It is 960 sq. ft. with a 12 foot ceiling. I would only work out there on weekends likely, but I would like to keep it at 5 to 10 *C with the option to bring it up a bit if I know I'm going to be working out there.

    I found a spreadsheet online to calculate heat loads and to keep it at 15*C inside with -15*C outside would take about 15000 BTU/hr, but we rarely see temps that cold. I found average temps for this area (the coldest average daily temp is only -3*C) and calculated the annual total heat load for every day under 10*C and came up with 27.5 million BTU.

    The first option I am considering is a mini-split heat pump. Mitsubishi has some models that provide rated heat output down to -15*C. The main advantages are no user effort and no floor space lost. The disadvantages are cost of the unit, although I would likely buy from ebay and do as much of the install myself as possible, and complexity. If anything ever goes wrong with the unit, there is very little I can fix myself. I am also concerned with under-performance in case my calculations are off. Electricity costs to cover my annual heat load would be about $400, although who knows where this will go.

    My second option is some kind of wood fired boiler. I put 2" insulation under the floating slab foundation and I have pex in the floor, just in case I ever wanted to use this option. We are set up to handle wood as we have an insert in the house and I don't mind the work or mess. I don't have a source of wood though, so I would have to buy it. My biggest concern is the initial cost of the boiler, does anyone know of a smaller, low cost, simple boiler that is still CSA or UL approved? I would build one, but don't want to void my insurance if anything ever happens. I would also like to incorporate storage, but maybe with the thermal mass of the concrete this isn't as important? The wood system appeals to me as I enjoy tinkering and it is simple enough to tweak and repair if necessary. If it gets really cold, it's not too hard to burn a bit more wood, whereas the heat pump may be in trouble, but with a heat pump, I could just turn on some electric heat if I really need it.

    Thoughts, concerns, and opinions are much appreciated!!
     
  2. henfruit

    henfruit
    Minister of Fire

    Nov 27, 2007
    711
    33
    Loc:
    New Hampshire-Maine border
    If are looking for a wood boiler,give Ted Kestor a call in Brockville ont.@613 349 9267. He is a Vigas dealer.
     
  3. paulm81

    paulm81
    New Member

    Feb 15, 2012
    29
    13
    Loc:
    Lucknow Ontario
    A fullsize boiler is out of the question price-wise just for the shop. For that much money, I could install the heat pump and enough solar panels to run it > no work and no fuel cost!! Are there any simple low-cost wood boilers available? Basically a firebox inside a tank?

    I would have no problem building something like this with all the proper safeties, but my insurance company will have a problem with it!!!
     
  4. 91LMS

    91LMS
    Member

    Oct 20, 2011
    217
    21
    Loc:
    MAINE
    i have seen a bunch of gassers for sale used for 1-2k.
     
  5. paulm81

    paulm81
    New Member

    Feb 15, 2012
    29
    13
    Loc:
    Lucknow Ontario
    I've been checking the classifieds around here and haven't seen anything even remotely suitable. I don't really know of many indoor boilers around here period, the outdoor ones seem more popular.

    Anyone have experience or opinions on the mini-split heat pumps?
     
  6. Floydian

    Floydian
    Feeling the Heat

    Dec 12, 2008
    459
    98
    Loc:
    Southwestern VA
    Hi Paul,

    Try a search on mini split heat pumps at: http://www.greenbuildingadvisor.com/

    Lots of good reading there,

    Noah
     
  7. Fred61

    Fred61
    Minister of Fire

    Nov 26, 2008
    2,012
    385
    Loc:
    Southeastern Vt.
    I have two mini-splits installed. One 9000 btu in the master bedroom and a 12000 btu unit in the main open living space. They are mainly used for cooling. I only use them for heat very early in the fall or very late in the spring to warm up on a chilly morning. They are useless when outside temperatures drop into the forties and the efficiency also diminishes as the outside temperature drops. They are about three years old and I have not kept up with what the latest and greatest advancements are in engineering of these units so you may find different numbers in your searches.
    I also have dual heat pumps in my RV that are tied in with the propane furnaces. When the outside temperatures drop to about +-45, the propane furnaces are activated.
     
  8. paulm81

    paulm81
    New Member

    Feb 15, 2012
    29
    13
    Loc:
    Lucknow Ontario
    I think this is my biggest concern, some of the new ones claim pretty impressive numbers, but how that translates into the real world is an expensive gamble.

    I think I'm pretty much set on using wood to heat the slab, but I still haven't found a simple low cost boiler.
     

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