Abstract :
IN MOST PARTS of the United States, heating plants must be adequate to heat our buildings from 0 to 70 degrees Fahrenheit. Actually this range varies with locality from a temperature difference of 100 degrees to one of only 35 degrees. It can be shown that the temperature span for heating, which largely determines size of plant, does not vary directly with the degree-day record (cumulative temperature deficiency below 65 degrees Fahrenheit). Even in the milder zones, heating requirements must include provision for occasional extremes of low temperature. The lowest recorded temperature need not be used as the basis for selecting building heating equipment, as this temperature minimum is approached only briefly and at long intervals. Through local experience, outdoor design temperatures may be derived. For fuel-fired plants, the design temperature is usually about 15 degrees above the lowest recorded, except in mild-winter areas.
