58SS
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58SS/DH
HEATING «COOLING
Induced-Combustion Gas-Fired Furnaces
Application Data
Installation Guidelines Procedures
INTRODUCTION
The desire to conserve energy has created
greater use of insulation, improved vapor barriers,
weather stripping, etc. Homes are now tighter, resulting
in less natural air infiltration and inefficient furnace oper
ation. The condition is further affected by the growing use
of kitchen and bathroom exhausts and even fireplaces.
Field studies indicate that combustion air starvation,
particularly in closet installations, points to a need for
positive furnace air supply, plus new guidelines for to
day’s furnace applications.
A WARNING
These instructions cover minimum combustion air
requirements and venting practices. They also reflect
current conditions found in the field, and conform to
existing national standards, and safety codes. In
some instances, these instructions exceed certain
local codes and ordinances, especially those that may
not have kept pace with changing construction
practices. Carrier requires these standard pro
cedures as a minimum for safe installation.
CONTENTS
INSPECTION
...................................................
1
FURNACE LOCATION — COMBUSTION/
VENTILATION AIR ...................................... 1
GAS PIPING................................................................... 3
VENTING.......................................................... 4
ELECTRICAL................................................................ 5
START-UP, ADJUSTMENT AND
SAFETY CHECK...................................................... 5
FURNACE LOCATION WITH RESPECT
TO COOLING EQUIPMENT................................. 7
SPECIAL LOCATIONS.............................................. 7
APPENDIX — VENTING REPLACEMENT
INSTALLATIONS..................................................... 7
INSPECTION
Check available power supply to be sure it meets speci
fications on wiring diagram and all motors in furnace.
Check available gas supply to see that it conforms to
gas specifications on AGA rating plate.
Page
A CAUTION
Do not block openings in front of furnace or on
furnace top along side vent pipe. These openings pro
vide air for combustion and ventilation. Never store
anything on or in contact with furnace, such as:
aerosol cans, rags, brooms and mops, cleaning tools
and aids, powders, bleaches, waxes, plastic items,
gasoline, kerosene, lighter fluids, cleaning fluids,
thinners, painting compounds or paper products.
Installation Procedures — These recommendations
apply to the installation and operation of gas furnaces
and piping systems for natural or LP (propane) gases.
Use these procedures in conjunction with your specific
furnace installation instructions.
Refer also to your gas supplier regulations and local
building, heating, plumbing and other codes for your
installation area.
Portions of the following have been adopted in part
from the National Fuel Gas Code (NFPA No. 54-1984 or
ANSI Z223.1-1984) copyrighted by the National Fire
Protection Association and American Gas Association.
For further details, consult this publication or current
edition available from NFPA, Batterymarch Park,
Quincy, MA 02269, or American Gas Association, 1515
Wilson Boulevard, Arlington, VA 22209.
FURNACE LOCATION —
COMBUSTION/VENTILATION AIR
Locate furnace close to chimney and as near to the
center of the air distribution system as possible. Install
furnace as level as possible. Provide ample space for
servicing and cleaning. Always comply with minimum
fire protection clearances shown on unit rating plate. Do
not install directly on carpeting, tile or any combustible
material other than wood flooring. Accessory eom-
bustible floor base is available from your dealer when
required.
The relief-air supply for the draft safeguard duct (draft
hood) must be in the same atmospheric pressure zone as
the combustion-air inlet supply to the furnace.
When a furnace is installed so that the supply ducts
carry air to areas outside the space containing the
furnace, the return air must also be handled by duct(s)
sealed to the furnace casing and terminating outside the
furnace location area.
All fuel-burning furnaces must be supplied with air
that enters the combustion process and then is vented to
the outdoors. Sufficient air must enter the space contain
ing the furnace to replace the amount drawn up the vent
stack. Replacement air must be provided by means of
ducts from the outside to the furnace area or heated
spaee. Under all eonditions, enough air must be provided
to ensure there will be no negative pressure condition
Bookh PC101 Catalog No 515-808 Printed in U S A Form 58D.S-2XA Pg 1 6-85 Replaces: 58D,S-1XA
Tab l6a
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
within the space containingHlte fut'^ace. A positive seal
must be made between the furnace base and platform
or return-air duct connections. Even a slight leak can
create a negative pressure condition in a confined closet
or basement and affect combustion. If necessary, seal the
furnace base-to-floor opening with fiberglass or other
approved material. Furnaces with side-connected returns
should use the factory-supplied bottom closure, properly
sealed.
For complete combustion and ventilation, the furnace
requires approximately 20 cu ft of air for every 1000 Btuh
of gas consumed. Thus, for each 1000 Btuh of gas con
sumed, a total of 20 cu ft of air must be supplied. For a
100,000-Btuh gas furnace, this equals 2000 cu ft of air per
hour (100 X 20) or 33 cu ft of air per minute (2000 60).
In the past, the infiltration of outside air assumed in heat
loss calculations (one air change per hour) was sufficient.
However, current construction methods using more insu
lation and vapor barriers, tighter fitting and gasketed
doors and windows, or weatherstripping, and the
presence of fuel-burning fireplaces and household
exhaust fans require positive introduction of outside air.
Use of exhaust fans, kitchen ventilation systems,
clothes dryers and fireplaces may create conditions that
require special attention to avoid unsatisfactory furnace
operation. Exhaust fans and range hoods can handle
from 60 to 300 cfm (or more). Gas and electric clothes
dryers remove even more air. Use of multiple appliances
requires special mandatory provisions for positive intro
duction of outside air. This makeup air requirement is
several times that required by the furnace and must be
replaced, in addition to the air required by the furnace.
A CAUTION
In addition, if ths building is of unusually tight con
struction, there shall be one permanent opening commu
nicating directly with outdoors. This opening shall have
a minimum free area of one sq in. per 5000 Btuh of total
input rating of all equipment in the enclosure. Ducts
shall be used to convey makeup air, and shall be of the
same cross-sectional area as the free area of the openings
to which they connect. This duct should be connected to
the cold air return of the heating system. The minimum
dimension of the rectangular air ducts should not be
less than 3 inches. See Fig. 1.
If furnace is installed on a raised platform to provide a
return-air plenum, and return air is taken directly from
the hallway or space adjacent to the furnace, all air for
combustion must come from the outside, as prescribed in
paragraph below.
ALL AIR FROM OUTDOORS — The confined space
shall be provided with 2 permanent openings, one com
mencing within 12 in. of the top and one commencing
within 12 in. of the bottom of the enclosure. These open
ings shall communicate directly, or by ducts, with out
doors. See Fig. 2.
a. When communicating with the outdoors through
horizontal ducts, each opening shall have a minimum
free area of one sq in. per 2000 Btuh of the total rated
input of all equipment in the enclosure. If vertical
ducts or openings with louvers and grilles are used,
each opening or duct shall have a minimum free area
of one sq in. per 4000 Btuh of the total rated input of all
equipment in the enclosure.
b. When ducts are used, they shall be of the same cross-
sectional area as the free area of the openings to which
they connect. The minimum dimension of rectangular
air ducts shall not be less than 3 inches.
Combustion air must come from a source not con
taminated by halogens, which include fluorides,
chlorides, bromides and iodides. These elements are
found in aerosols, detergents, bleaches, cleaning
solvents, salts, air fresheners and other household
products. Vapors from these products are highly
corrosive to gas-fired furnaces, even in extremely low
concentrations — as low as 1/2 part per million.
When such contaminants are present, outside air
must be ducted separately to the furnace room.
Requirements for combustion and ventilation air
depend upon whether furnace is located in a confined or
unconfined space. An unconfined space is defined as a
space where volume is not less than 50 cu ft per 1000 Btuh
of the total input rating of all appliances installed in that
space. Rooms directly open (no doors) to the space in
which the appliances are installed are considered a part
of the unconfined space. A confined space is defined as a
space with volume less than 50 cu ft per 1000 Btuh of the
total input ratings of all appliances in that space.
Furnaces in Confined Spaces (Typical Furnace
Closet)
ALL AIR FROM INSIDE BUILDINGS — The con
fined space shall be provided with 2 permanent openings,
one beginning within 12 in. of the top and one beginning
within 12 in. of the bottom of the enclosure. Each opening
shall have a minimum free area of one sq in. per 1000 Btuh
of the total input rating of all equipment in the enclo
sure, but not less than 100 sq inches. The openings must
freely communicate with other interior areas served by
the furnace, of sufficient volume so that the combined
volume of all spaces meets the criteria for an unconfined
space. This can be accomplished through either per
manent openings or louvered doors.
Furnaces in Unconfined Spaces (Basements,
Large Equipment Rooms, etc.) — If the uncon
fined space is within a building of unusually tight con
struction, air for combustion, ventilation and dilution of
flue gases shall be obtained from outdoors or from spaces
freely communicating with the outdoors. A permanent
opening, or openings, having a total free area of not less
than one sq in. per 5000 Btuh of total input rating for all
equipment shall be provided. A duct may be used to con
vey makeup air from the outdoors and shall be of the
same cross-sectional area as the free area of the openings
to which it connects. The duct may be connected to the
cold air return of the heating system only if it connects
directly to outside air. The minimum dimension of
rectangular air ducts shall be not less than 3 inches.
A CAUTION
Return air must not be taken from the room, unless
an equal or greater amount of air is supplied to the
room. All duct connections to the furnace must be
airtight to avoid causing a negative pressure condi
tion within the room.
Louvers and Grilles — In calculating the free area,
consideration shall be given to the blocking effect of
louvers, grilles, or screens protecting openings. Screens
used must not be smaller than 1 / 4-in. mesh. If the free
area through a design of louver or grille is known, it
should be used in calculating the size opening required to
provide the free area specified. If the design and free area
is not known, assume that wood louvers will have 20 to
25% free area and metal louvers and grilles will have
60 to 75% free area. Louvers and grilles that provide
combustion and dilution air must be constructed so they
cannot be closed.
©
RETURN OR
SUPPLY AIR
pl~1
I I I
I I I
I I I
VENT TO ROOF
12 IN. MAX
I so IN. PER
2000 BTUH
DUCTS TO
OUTSIDE
I SO IN. PER
2000 BTUH
12 IN. MAX
±
T
I so IN. PER
4000 BTUH
DUCTS
TO ROOF
I I
I I
T
i
RETURN
OR
SUPPLY
AIR
VENT
TO ROOF
1 3
-12 IN.MAX
* MINIMUM OPENING SIZE IS 100 SO IN. (REUIRN
+ MINIMUMOF 3 IN. WHEN TYPE-BI VENT IS USED. AIR ONLY)
Fig. 1 — Upflow or Counterflow, Using Air
from Inside Building
GAS PIPING
Gas piping must be installed in accordance with
national and local codes.
The gas supply line should be a separate line directly
from the meter to the furnace, if possible. Referto Table 1
for recommended gas pipe sizing.
Table 1 — Maximum Capacity of Gas Pipe*
NOMINAL
IRON PIPE
SIZE
(in.)
'k
% 0.824
1 1.049
r/4
1V2
'Cubic ft of gas per hour for gas pressure of 0.5 psig or less, and a
pressure drop of 0.5 in wg (based on a 0 60 specific gravity)
Ref. Table C-4 NFPA 54-1984.
INTERNAL
DIAMETER
(in.)
0 622
1 380 1400 950
1 610 2100 1460 1180
LENGTH OF PIPE (ft)
10 20 30
175 120 97
360 250 200
680 465 375
40
50
82 73
170
151
285
320
770 660 580
990 900
RETURN OR
SUPPLY AIR
USE ANY OF THE FOLLOWING COMBINATIONS
OF OPENINGS; AaB CSD D8E
J
TO OUTSIDE
5
DUCT
I so IN. PER
4000 BTUH
Fig. 2 — Upflow or Counterflow, Using Air
from Outside Building
Install a sediment trap in the riser leading to the
furnace. This trap collects dirt or condensate. It can be
installed by connecting a Tee to the riser leading to the
furnace, so that the straight through section of the Tee
is vertical. Then connect a capped nipple into the lower
end of the Tee. The capped nipple should extend below
the level of the gas controls. See Fig. 3. Where a gum filter
is required by local codes, install it in accordance with
Avoid low spots in long runs of pipe. It is best to slope
all pipe I/4inch in 15 ft to prevent traps. All horizontal
runs should slope away from the meter, to risers. Risers
should be used to connect to the furnace and to the meter.
Joint compounds (pipe dope) should be applied
sparingly and only to the male threads of the joints.
Consult local supplier for type of compound to be used.
This pipe dope must be resistant to the action of LP
(propane) gas.
An accessible manual shutoff valve shall be installed
upstream of the furnace gas controls and within 6 ft of the
furnace. A 1/8-in. NPT plugged tapping, accessible for
test gage connection, must be installed immediately up
stream of the gas supply connection to the furnace, and
downstream of the manual shutoff valve.
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