GAS FIRED VENTED FLOOR FURNACES
7
FLOOR FURNACE LOCATION
Choose a central location such as a hallway but where
occupant traffic is minimal & where there is at least 18
inches of room from two adjoining sides of the grill to the
nearest wall so that occupants may pass without stepping
on the grill.
Figure 1
Give consideration to available air for combustion, location
in relation to chimney or vent system, thermostat location,
clearance under floor, clearance to combustibles, and
heat circulation. Any open foundation is unacceptable as
wind can cause pilot outage and reduced efficiency. Keep
furniture, drapes, doors, and other combustible materials
at least 12 inches from the edge of the grill. Never locate
the floor furnace closer than 8 inches to a wall and never in
a corner.
Figure 2
Two adjoining sides of the floor furnace must have a
minimum clearance of 18".
Figure 1
After selecting a location in the home, go beneath the
floor and check the position of the floor furnace in relation
to joists, supporting columns, electric wires, water pipes
and walls. There must be a minimum of 6 inches clearance
between the top of the draft hood and floor joists. There
must also be at least 6 inches clearance between the
bottom of the floor furnace and the ground.
Figure 3
In order to find the location beneath the floor it may be
necessary to drill a 1/16 inch hole through the floor approximately
in the center of the selected floor furnace location to use as a
reference point when measuring under the floor.
FRESH AIR FOR COMBUSTION AND VENTING
Adequate air for combustion and venting must be
provided.
Any reduction in the necessary amount of
fresh air can result in an oxygen starved flame that
emits Carbon Monoxide (C.O.) an odorless, colorless
gas that can cause serious injury or death.
A ventilated crawl space will usually provide enough fresh
air. However, you must check to see that there is 1 square
inch of free area of ventilation opening for each 1,000
BTU’s input of your floor furnace.
To compensate for the loss of square inches of
ventilation due to the use of louvers, grills, or screens add
approximately 50% to the square inches calculated. Screen
all openings with mesh not less than 1/4 inch to prevent
animals or insects from entering the crawl space.
All type “B” vents shall ext end in a generally vertical
direction with offsets not exceeding 45 degrees, except
that a vent system having not more than one 60 degree
offset may be allowed.
Any angle greater than 45 degrees from the vertical is
considered horizontal. The total horizontal run of a vent
plus the horizontal vent connector shall be not greater
than 75 percent of the vertical height of the vent.
Any offsets used should be as far above the drafthood
as possible to allow a venting action to begin before any
restriction is encountered.
Kitchen
Bath
Bedroom
Bedroom
Living Room
18" Minimum
Thermostat
Vent Pipe
WALL
8" Minimum
FLOOR
FURNACE
FLOOR
6" Minimum
JOIST
JOIST
6" Minimum
GROUND LEVEL
DRAFT
HOOD
VENT PIPE
If another gas burning appliance, such as a water heater,
is installed within the same crawl space or basement:
Add the BTU’s of the other appliance to those of the floor
furnace before calculating the total ventilation needed.
FIGURE 1
FIGURE 2
FIGURE 3
EXAMPLE 1
50,000 BTU FLOOR F 1,000 = 50 SQUARE INCHES
EXAMPLE 2
50,000 BTU
FLOOR
FURNACE
40,000 BTU
WATER
HEATER
+
1,000 = 90 SQUARE
INCHES
+
