Sizing Guide

4 Sizing Guide www.hartandcooley.com
Type B Double-Wall Gas Vents
Systems
The Tables given in Section 1 apply to system design using
Hart & Cooley
®
Type B Gas Vents and to Model TLC
Chimneys when used for venting listed Category I gas-
fired, draft-hood-equipped or fan-assisted combustion
appliances. At no time should a venting system for a listed
Category II, III, or IV appliance be sized with these tables;
instead, follow the appliance manufacturer’s instructions.
Clearance
Installations must provide the proper clearances to
combustible materials as specified in the appropriate
Underwriters Laboratories Inc. conditions for Listing,
as stated in the product catalogs and embossed on the
vent pipe. Hart & Cooley
®
systems to be designed using
Section 1 of this Guide are shown below with their
proper clearances.
Type B Hart & Cooley
®
pipe sizes 3 through 24 inches
in diameter require 1 inch of airspace
clearance throughout the entire length.
Model TLC Hart & Cooley
®
chimney sizes 5 through
14 inches in diameter require 2 inches of
airspace clearance to combustible
construction.
Air Supply†
For satisfactory performance of appliances in confined spaces
and for the venting system, an adequate supply of fresh air
must be provided. When proper air supply has been provided
for other appliances, such as clothes dryers, range hoods,
fireplaces, etc., then the following method as provided by
NFPA Standard 54, ANSI Z223.1 will provide the additional air
needed for the appliances. The two grilles specified in A, B, C
and D of Figure 1 must be installed so that one is at or below
A
B
D
E
C
VENTILATION
LOUVERS
(each end of attic)
VENTILATION LOUVERS
(each end of attic)
VENTILATION LOUVERS
(each end of attic)
AIR DUCT
INLET
(terminate 1 ft.
above floor)
ALTERNATE
AIR INLET
ALTERNATE
AIR INLET
VENTILATION
LOUVERS
FOR UNHEATED
CRAWL SPACE
AIR
SUPPLY
OPENINGS
AIR
SUPPLY
OPENING
OUTLET
AIR DUCT
OUTLET AIR
INLET AIR
OUTLET
AIR DUCT
INLET
AIR DUCT
ALL AIR FROM
INSIDE BUILDING
ALL AIR FROM
OUTDOORS THROUGH
HORIZONTAL DUCTS
**ALL AIR FROM VENTILATED
ATTIC OR ADJACENT TO
EXTERIOR WALL
AIR IN FROM CRAWL
SPACE, OUT INTO ATTIC
SINGLE OPENING, ALL AIR
FROM OUTDOORS
Free Area of
Each Grille
Total Input*
1000
=
Free Area of
Each Grille
Total Input*
4000
=
Free Area of
Each Duct
Total Input*
2000
=
Free Area of
Each Duct
or Grille
Total Input*
4000
=
(Use 2 grilles facing into large
interior room. Minimum free
area of each grille is 100 sq. in.)
*Total Input = Total of
combined appliance input
ratings in BTU; (Free Area
in square inches).
**If the equipment room is
located against an outside
wall and the air openings
communicate directly with
the outdoors, each opening
shall have a free area of not
less than one square inch
per 4,000 Btu per hour of
the total input rating of all
equipment in the enclosure.
†See NFPA 54 for additional
provisions and restrictions
for the air supply.
the combustion air inlet of
the appliance (within 12"
from the floor) and the
other above the relief
opening of the draft hood
(within 12" from the
ceiling). The minimum
dimension of air opening
shall be 3". Any ducting
used should have at least
the same free area as the
grilles determined.
One permanent opening,
commencing within
12 inches of the top of the
enclosure, shall be
permitted where the
equipment has clearances
of at least 1 inch from the
sides and back and 6
inches from the front of
the appliance. The
opening shall directly
communicate with the
outdoors or shall
communicate through a
vertical or horizontal duct
to the outdoors or spaces
that freely communicate
with the outdoors (see
Figure 1, E) and shall
have a minimum free area
of:
Figure 1