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System design temp.

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Michael Rogers
Michael Rogers Member Posts: 29
in THE MAIN WALL
I just did a heatloss calc. on my house and was working with a system temp. of 180*F. So to keep the house 70* with an outside temp of -20*F it is going to take 99,500 bth/hr. Am I working with too low of an outside temp. for sourthern Ontario or does that sound fair. The house is 1947 two story, partially insulated, with leaded glass windows and original storms. The basement is unfinished with one rad. but I would like to do infloor and finish it. If 100,000 btu/hr is right, I should probabaly go with a 120k btu boiler? I am going to do this job in the spring so I will be lurking here till then, thank you. P.S. The current boiler is originally coal, converted to oil, converted to gas.....ie it is a pig.

Comments

  • Michael Rogers
    Michael Rogers Member Posts: 29


    By the by this is a gravity sys. that will be converted to a primary/secondary setup.
  • Bob W._3
    Bob W._3 Member Posts: 561


    According to the sites on Google your design temp should be in the Ontario Building Code. Can't seem to find it online though. Here is a link to their search page:

    http://www.canlii.org/on/laws/regu/1997r.403/
  • Michael Rogers
    Michael Rogers Member Posts: 29


    I think I found it. So for Brantford ON, I would calc. for -17°C or 1.4°F. It also said "using 2.5 per cent design temperature criteria". What exactly does that mean? Here is the table. www.canlii.org/on/laws/regu/1997r.403/20051216/part1_1997r.403_2.gif
  • Brad White_22
    Brad White_22 Member Posts: 15
    2.5 percent means

    that is the percentage of total annual hours at which the temperature will be at the specified point or above.

    ASHRAE and the US Air Force has design data expressed at 0.4 percent, 1 percent and 2.0 percent (not 2.5 for some reason) all on the cooling side and conversely 99.6 percent, 99 percent and 97.5 percent on the heating side of the season.

    I will search my files to see if I have any USAF data for Southern Ontario as a basis of comparison. If I do, it will be in .pdf format and has interesting graphs. They run about 18 pages for each location.

    Brad
  • Brad White_22
    Brad White_22 Member Posts: 15
    Weather Data for S. Ontario

    All I could find for Ontario:
    Ottawa, Toronto/Pearson AP, Timmins (Hometown of Shania :) and a a place with named "Thunder Bay" that seem positively uninhabitable ;).

    You have a few places with "Bay" by the way, with similar weather. I would send them some heat.
  • Michael Rogers
    Michael Rogers Member Posts: 29


    So what could I safely use a design temp and do my heat loss calc again to size the boiler. This will make a big differance in my sizing. You gotta love Canada where you go from 95°F in the summer to -20°F in the winter.
  • Bob W._3
    Bob W._3 Member Posts: 561


    Brad, I think you meant "at or below" the specified point? My understanding is that in an average heating year there will only be 2.5 percent of the time when it is at or below design temperature.

    BTW, I find that totally inadequate, as we can have temps well below design temp that linger for far too long. Our design temp is -17F. I have seen days where it hit -33 to -35 and never got above -17, with a high wind no less. House would get pretty cold if all your system could do was the design temp.
  • jp_2
    jp_2 Member Posts: 1,935
    confused???

    you say your temp swings are from 95 to -20F? if true do not use 0F as design temp?
  • Bob W._3
    Bob W._3 Member Posts: 561


    Thunder Bay is on Lake Superior north of Duluth. It used to be two cities, Port Arthur and Fort William.
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    At or above

    is correct in that the higher percentage numbers (e.g. 97.5%) are reserved for the winter low end design values. The inverse is true in that for this example it would be colder 2.5% of the time.
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Not sure exactly where you are

    What city is closest to the ones I posted? Those are all I could find in my database.

    They are pretty spread out but you have a choice. I tend to use the narrowest band (99.6%) for heating design, especially where radiation is concerned. Yes, it makes a big difference especially a 10 or 20 degree spread between the 97.5 and 99.6 percent columns.
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    I found it on the map

    and am amazed that it can still be called "southern Ontario". I swear, there is nothing outdoors in it's liquid state in winter in Thunder Bay. Dogs frozen to hydrants...bet it gets ugly :)
  • Michael Rogers
    Michael Rogers Member Posts: 29


    The nearest city to me on that list is Toronto. I am about 40 mile west of there. I was planning to size it for -17°F, but would like to hear other opinions.
  • ChasMan
    ChasMan Member Posts: 474


    Like Hamilton or Burlington? They are slightly warmer than Toronto. At least according to HVAC Calc.
  • Michael Rogers
    Michael Rogers Member Posts: 29


    Yes, Hamilton. Brantford is 20mins. Southwest of Hamilton. Now we are getting closer. Thunder Bay is 570 miles Northwest of me.
  • Brad White_23
    Brad White_23 Member Posts: 8


  • Michael Rogers
    Michael Rogers Member Posts: 29


    I will design the system for about -17°F. I think it should be ok as I also plan on upgrading insulation and windows.
This discussion has been closed.

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