Williams 2509621 Installation & Operating Instruction Manual page 9

Combustion & Ventilation Air (Con't)
A. All Air From Inside Building:
If the confined space adjoins an unconfined space as
defined in EXAMPLE 1, provide two permanent openings,
one within 12 inches of the top and one within 12 inches
of the bottom of the room connecting directly to unconfin-
ed space. Each opening must have a free area of at least
100 square inches or 1 square inch per 1000 Btuh com-
bined input of appliances in one room if combined input
exceeds 100,000 Btuh.
WARNING
DANGER OF PROPERTY DAMAGE,
BODILY INJURY OR DEATH
THE ADJOINING UNCONFINED SPACE MUST
HAVE ADEQUATE AIR INFILTRATION AS DEFINED
IN EXAMPLE 1.
FOR EXAMPLE: Your furnace is rated at 50,000 Btu per
hour. The water heater is rated at 30,000 Btu per hour.The
total is 80,000 Btu per hour. You need two grilles, each with
100 square inches of free opening. Metal grilles have about
60% free area, so you need two metal grilles each with
160 square inches of Iouvered area.
Refer to Fig. 5, which shows grille installation.
Using the previous example, the two connecting rooms
plus the closet must equal at least 500 sq. feet to handle
the combined input 50,000 plus 30,000.
GRILLES CONNECTING ROOMS TO
MAKE UNCONFINED SPACE
VENTILATION GRILLES CONNECTING
TWO ROOMS TO MEET UNCONFINED
$PAC_
I I
I
, I
200 SO IN
MINIMUM
BETWEEN
LARGE ROOMS
1<[ COMMENOt O
FRESH AIR DUCT
rPilO CRAWL $PAC_ _N
_ U_NACE AREA
OR IN CLOS[T W_IH WAIER HLA1FR
so
_N
100
So
IN
B. All Air From Outdoors:
If confined space doesn't adjoin an unconfined space
(defined in EXAMPLE 1) then air must be provided from
outdoors or spaces open to outdoors such as attic or crawl
spaces.
Provide two permanent openings, one within 12 inches of
top, one within 12 inches of bottom of room connecting
directly, or by using ducts, with the outdoor or areas open
to outdoors.
If opening connects directly to, or with vertical ducts, the
free area of each opening must be at least 1 square inch
per 4000 Btuh combined input of appliances in area.
If horizontal ducts are used, the free area of each opening
must be at least 1 square inch per 2000 Btuh combined
input of appliances in area.
FOR EXAMPLE: Your furnace is rated at 50,000 Btu
per hour. The water heater is rated at 30,000 Btu per
hour. The total is 80,000 Btu per hour. You need two
grilles, each with 20 square inches of free opening,
unless connected by horizontal ducts which would re-
quire each grille or opening to have a free area of 40
square inches.
CH_MN[ y
OR GAS VENT
3 OR CRAWL SPACE
OUTLET AIR
==
o-=
PNLEI AIR
*Openings for inlet or outlet air should not be made into
attic area if attic is equipped with a thermostat controlled
power vent.
FREE AREA IN SQ. INCHES
EACH OPENING (FURNACE ONLY)
BASED ON ONE SQ. INCH PER 4000 BTUH
Furnace
Btuh/Input
30,000
35,000
40,000
45,000
50,000
60,000
Sq.
Inch
of Opening
7.5
8.75
10.0
11.25
12.5
15.0
Req'd Number of Holes
Sill or Header Plates
1V=" 2" 3"
7 4
8 5
9 5
10 6
11 6
13 8
2
2
3
3
3
4
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