FIGURE I

Heating Load Hours (HLH) for the United States and Territories

Alaska

This map is reasonably accurate for most parts of the United States but is necessarily highly generalized
and consequently not too accurate in mountainous regions, particularly in the Rockies.

Hawaii and Territories

FIGURE 2

Test Setup for Measuring S/F for Furnaces and Boilers
with Barometric Draft Controls

AVERAGE OUTDOOR AIR TEMPERATURE (°F)

60

FIGURE 3

Average Outdoor Air Temperature vs. Balance Point Temperature for
Modulating Furnaces and Boilers

BALANCE POINT TEMPERATURE TĊ (°F)

This figure is based on 5200 degree-days and 5°F outdoor design temperature.

FIGURE 4

Fraction of Total Annual Heating Load Applicable to Reduced Operating
Mode (X,) and to Maximum Operating Mode or Modulating Mode (X2) vs.
Balance Point Temperature for Modulating Furnaces and Boilers.

1.0

0.0

FRACTION OF TOTAL ANNUAL HEATING LOAD APPLICABLE TO REDUCED OPERATING MODE (X1)

BALANCE POINT TEMPERATURE TC (°F)

This figure is based on 5200 degree-days and 5°F outdoor design temperature.

[49 FR 12159, Mar. 28, 1984]

FRACTION OF TOTAL ANNUAL HEATING LOAD APPLICABLE

TO MAXIMUM OPERATING MODE OR MODULATING MODE (X2)