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99% Winter Design Temperatures for the Contiguous United States
−10
o
5
F
o
17
F
o
27
F
o
37
F
This map is a necessarily generalized guide to temperatures in the contiguous Unites States. Temperatures shown for areas such as
mountainous regions and large urban centers may not be accurate. The data used to develop this map was taken from the 1993 ASHRAE
Fundamentals Handbook (Chapter 24, Table 1: Climate Conditions for the United States.
This map has been reprinted with permission from NFPA 54: National Fuel Gas Code E1999, National Fire Protection Association, Quincy,
MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject,
which is represented only by the standard in its entirety.
Table 2 lists winter design temperatures for some of the
major U. S. cities.
TABLE 2
Minimum Winter Design Temperatures
of Major U. S. Cities
City
Baltimore
Boston
Chicago
Columbus, OH
Des Moines
Detroit
Kansas City
New York
Philadelphia
Pittsburgh
Salt Lake City
St. Louis
Requirements
The room temperature surrounding the furnace and vent
connectors must be at least 60°F (16°C).
o
F
o
−10
F
Minimum Winter Design
Temperature −− °F (°C)
+10°F (−12°C)
+6°F (−14°C)
−8°F (−22°C)
0°F (−18°C)
−10°F (−23°C)
+3°F (−16°C)
+2°F (−17°C)
+11°F (−12°C)
+10°F (−12°C)
+1°F (−17°C)
+3°F (−16°C)
+2°F (−17°C)
FIGURE 1
The space surrounding the furnace must not be
depressurized by more than 0.2" w.c. below the outdoor
pressure (caused by exhaust fans, clothes dryers, etc.)
Furnace capacity must not exceed 1.7 times the
calculated heating load.
Sea level input ratings should be used when determining
maximum capacity for high altitude installation.
If the furnace is to be vented into an exterior chimney, the
furnace must share a common vent with at least one
drafthood−equipped appliance to prevent condensation in
the masonry chimney.
If the furnace is to be vented into an interior chimney, the
furnace may be vented as a single appliance or into a
shared vent.
Chimney and Vent Connector
Requirements and Sizing
The masonry chimney vent adapter kit may only be used
in applications which include vent exit through the
furnace top cap. Applications which require side vent
exit are not permissible.
When two or more appliances are vented into a single
masonry chimney, the flow area of the largest section of
vertical vent shall not exceed seven times the flow area
of the vent adapter outlet or drafthood outlet , whichever
is smaller, unless the vent is designed in accordance
with approved engineering methods.
Page 2
−10
o
F
o
5
F
o
17
F
o
27
F
o
37
F
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