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Design temps

Brad White_191
Brad White_191 Member Posts: 252
in THE MAIN WALL
Not a lot to add but if you give me your location, I can probably find specific weather data for you.

Comments

  • Mike Dunn
    Mike Dunn Member Posts: 189
    How do you guys

    determine your outdoor design temp? Do you simply use the design temp that your heat loss software recommends for your area or are there some other ideas? What if you do a heat loss by hand?

    In a perfect world what number would we all use to remain consistant?

    Mike
  • Unknown
    Unknown


    ASHRAE's 99.6% design temp from the weather station nearest that best reflects the area. sometimes corrected for local microclimate issues based on job site situations (high elevation, perhaps).

    a perfect world would also have to take into account the mass of the home, solar gain, lighting, occupancy rates, wind and soil composition, night time cloud cover, climate, and a hundred other factors ;)

    Load calculations are an art, not a science. Energy use calculations on existing buildings is a science.
  • MIke_Jonas
    MIke_Jonas Member Posts: 209
    Like Rob said..

    The software I use has the ASHRAE standards built in. With a couple mouse clicks, I can change it and see how it affects boiler sizing.

    For instance, Chicago-Midway airport (by my house) has a design temp of 0. O'hare airport is -4. I'll try -5 and -10. Most of the time, the heat loss with these different design temps is within whatever size boiler I would have quoted at 0.

    As an example, say, a Knight 105 would be too small at 0 design temp, so I have to quote a 150. The 150 may cover the heat loss to -10 as well. I let the homeowner know that what I size will handle ASHRAE design temps, and then some.

    I have had some customers...."I remember 20 years ago, it got down to 15 below, for two weeks straight. We were cold. I want a boiler that will keep me warm when that happens again". I show them what design temp calls for, show them what 15 below calls for and let them choose.

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