Williams 509622A Owner's Manual & Installation Instructions page 10

INSTALLING YOUR FURNACE
HOLE PLACEMENT - EXAMPLE
AIR GRILLS TO STUD SPACE
HOLES FROM VENTILATED
CRAWL SPACE INTO STUD SPACE
HOLES IN BOTTOM ON BACK OF FURNACE INTO OPEN
STUD SPACE OR CRAWL SPACE
FURNACE LOCATED IN UNCONFINED SPACE
An unconfined space must have a volume of a minimum 50
cubic feet per 1,000 BTU/hr. of the total combined input of
all appliances in the area. Adjoining rooms may be included
only if there are no doors between the rooms or if special
provisions are made such as ventilation grilles installed
between connecting rooms. Figure 4 outlines the minimum
area in square feet, based on 8-foot ceiling heights for various
BTU/hr. input ratings.
FIGURE 4 - MINIMUM AREA
4,000 BTU/hr. per
square inch opening
Rectangular
Round duct dia. square duct size
4ʺ 3ʺ x 3ʺ
4ʺ 3ʺ x 3ʺ
4ʺ
3ʺ x 4ʺ
4ʺ
3ʺ x 4ʺ
4ʺ
3ʺ x 5ʺ
4 ½ʺ 3ʺ x 5ʺ
* Can be two or more rooms separated by ventilation gas fire.
10
MONTEREY TOP VENT GAS WALL HEATER
HOLES FROM VENTILATED
ATTIC INTO STUD SPACE
12ʺ MAX FROM FLOOR
*Uncontained space
Max. min. area in sq. ft.
BTU/hr input 8ʼ ceiling height
30,000 145
35,000 219
40,000 240
281
45,000
312
50,000
375
60,000
EXAMPLES OF GRILL PLACEMENT
VENTILATION GRILLES CONNECTING TWO
ROOMS TO MEET UNCONFINED SPACE
200 SQ IN
MINIMUM
BETWEEN
LARGE
ROOMS
RECOMMENDED FRESH AIR DUCT INTO CRAWL
SPACE IN FURNACE AREA OR IN CLOSET WITH
WATER HEATER
FURNACE LOCATED IN CONFINED SPACE
If a furnace is installed in a confined space, it must be
provided with free air for proper combustion and ventilation
of flue gases by one of the following methods:
A. AIR FROM INSIDE THE BUILDING
If the confined space adjoins an unconfined space, provide
two permanent openings. One within 12-inches of the top
and another within 12-inches of the bottom of the room
directly connected to the unconfined space. Each opening
must have a free area of at least 100-square inches or 1-square
inch per 1,000 BTU/hr. of input for all appliances combined.
WARNING: Danger of property damage, bodily
injury or death. The adjoining unconfined space must
have adequate air infiltration.
B. AIR FROM OUTDOORS
If confined space does not adjoin an unconfined space, then
air must be provided from outdoors or spaces open to the
outdoors such as an attic or crawl spaces.
Openings for inlet or outlet air should NOT be made into an
attic area if the attic is equipped with a thermostat controlled
power vent.
Provide two permanent openings, one within 12-inches of
the top and bottom of the room connecting directly to, or by
using ducts, with the outdoors or areas open to fresh air.
If the opening connects directly to, or with vertical ducts, the free
area of each opening must be at least 1-square inch per 4,000
BTU/hr. of the combined input of all appliances in the area.
If horizontal ducts are used, the free area of each opening
must be at least 1-square inch per 2,000 BTU/hr. of the
combined input of all appliances in the area.
100 SQ IN
VENTILATION
GRILLES
INTO CLOSET
FOR HOT
WATER
HEATER
100 SQ IN