Case 2: Furnace Located In A Confined Space; Case 3: Furnace Located In A Confined Space, Outdoor Air From Attic Or; Crawl Space - Napoleon WPV-N Série Instructions D'installation Et D'opération

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8.1.2 CASE 2: FURNACE LOCATED IN A CONFINED SPACE

A confi ned space, (any space smaller than the minimums discussed in Case 1), must have two air openings;
one within 12" (305mm) of the ceiling and the other within 12" (305mm) of the fl oor. The air openings must be
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sized considering the method outside air is introduced, whether the combustion and ventilation air is being
taken from indoors or outdoors and taking into account any other fuel burning appliances in the confi ned
space.
If suffi cient indoor combustion and ventilation air is available for the furnace and all other fuel burning
appliances, size each opening on the basis of one square inch (645mm²) of free area per 1000 Btu/hr.
(Figure 4)
NOTE
Be sure to consider all clothes dryers, bathroom fans, range hoods, etc., when making this calculation.
The minimum requirement for these openings is 100
square inches (645mm²), even for the furnace models
under 100,000 Btu/hr.
NOTE
If using grills to cover the two openings, factor in the
free area of the grill. Typically, a sidewall grill will
have a free area approximately 50% of its nominal
size. Consequently, if the required opening is 10" x
10" (254mm x 254mm), it will have to be doubled if
using a sidewall grill with 50% free area.
IMPORTANT:
IF AN EXHAUST FAN, FIREPLACE, CLOTHES DRYER OR ANY SIMILAR DEVICE IS PRESENT IN THE
INDOOR AREA FROM WHICH THE COMBUSTION AND VENTILATION AIR WILL BE DRAWN, NEGA-
TIVE PRESSURE COULD BE A PROBLEM IF NATURAL INFILTRATION FROM THE OUTDOORS DOES
NOT MATCH THE RATE AT WHICH AIR IS EXHAUSTED.
8.1.3 CASE 3: FURNACE LOCATED IN A CONFINED SPACE, OUTDOOR AIR FROM ATTIC
In this circumstance, the free area of each of the two combustion and ventilation air openings is based on a
minimum of 1 square inch (645mm²) per 4000 Btu/hr. In this confi guration, one opening can originate from the
fl oor drawing combustion and ventilation air from the ventilated crawl space.
The other opening may communicate freely with the ventilated attic. If using the attic air, ensure that the
opening is ducted from the ceiling high enough to be above the insulation. The attic must be adequately
vented with soffi t vents or gable vents (Figure 5).
As an alternative to creating an opening in the fl oor to draw air from a crawl space, a duct may be dropped from
the attic terminating 12" (305mm) above the fl oor.
W415-2308 / B / 11.04.19
OR CRAWL SPACE
FIGURE 4 - COMBUSTION/DILUTION AIR FROM
HEATED INSIDE SOURCES (CASE 2)
H13.2C