Page 1
Number One
AirConditbninq
Maker
Division o1
Carrier Corporation
Carrier Parkway • Syracuse NY 13221
V
-------
U-
Procedures for Gas-Fired Furnaces
INTRODUCTION
The Need for Adequate Combustion Air —
Modern construction methods involve greater use of
insulation, improved vapor barriers and weather
stripping, with the result that both apartments and
single-family residences generally are much tighter
structurally than they have been in the past.
Combustion air supply for gas-fired equipment can
be affected by these construction conditions, be
cause infiltration that existed in the past may not
now be adequate. Extensive use of kitchen and bath
room exhaust fans, and even fireplaces, aggravates
the situation.
Today’s building practices invalidate the old rule
of thumb of “one air change by infiltration.” Reli
ance on this practice can result in combustion air
starvation if proper combustion air is not provided.
In fact, recent field investigations, particularly with
closet installation of gas-fired furnaces, indicate the
need for positive provision for combustion air and
for a better understanding of application guidelines
that relate to today’s conditions.
These instructions cover minimum combustion
air requirements and venting practices, 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 the changing resi
dential construction practices. Carrier requires these
standard procedures as a minimum for a safe
installation.
CAUTION: Do not obstruct openings in front
of the furnace or in the top on each side of the
vent pipe. These provide air for combustion and
ventilation. Never store anything on or in con
tact with the furnace such as;
Spray or aerosol cans, rags, brooms, dust mops,
vacuum cleaners, or other cleaning tools.
Soap powders, bleaches, waxes or other clean
ing compounds, plastic or plastic containers,
gasoline, kerosene, cigarette lighter fluid, dry
cleaning fluids, or other volatile fluids.
Paint ihinners and other painting compounds,
paper bags or other paper products.
Installation Procedures — The following recom
mendations apply to the installation and operation
of gas furnaces and piping systems for natural and
LP gases. Use these procedures in conjunction with
the specific furnace installation instructions.
Refer also to the regulations of the serving gas
supplier and the local building, heating, plumbing
or other codes in effect in the area in which the
installation is made.
Portions of the following have been adopted in
part from the “National Fuel Gas Code” (NFPA
No. 54-1980 or ANSI Z223.I-I980) copyrighted by
the National Fire Protection Association and
American Gas Association. For further details, con
sult this publication or current edition available
from NFPA, 470 Atlantic Avenue, Boston, MA
02210, or American Gas Association, 1515 Wilson
Boulevard, Arlington, VA 22209.
These instructions contain the following sections:
Page
Inspection
...............................................................
1
Location and Air for Combustion
and Ventilation.................................................. I
Gas Piping.............................................................. 4
Venting..................................................................... 4
Electrical.................................................................. 5
Start-Up, Adjustment, and Safety Check .... 5
Furnace Location with Respect to
Cooling Equipment........................................... 7
Special Locations
...
................................................
INSPECTION
7
Check the available power supply to be sure that
it meets the specifications on the wiring diagram
and all motors in the furnace.
Check the available gas supply to see that it con
forms to the gas specification on the AGA rating
plate.
LOCATION AND AIR FOR COMBUSTION
AND VENTILATION
Locate the furnace close to the chimney and as
near the center of the air distribution system as
possible. Provide ample space for servicing and
cleaning. Always comply with minimum fire protec
tion clearances shown on the unit rating plate. Do
not install directly on carpeting, tile or any com
bustible material other than wood flooring. If base
for combustible floor is required, obtain from
Carrier distributor or dealer.
© Carrier Corporation 1982 Form 58-9XA
Page 2
The draft hood relief air supply must be in the
same atmospheric pressure zone as the combustion
air inlet supply to the furnace.
When a furnace is installed so that 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 space containing the furnace.
All fuel-burning equipment must be supplied with
air, which enters into the combustion process and is
then vented to the outdoors. Sufficient air must
enter the equipment room to replace that drawn up
the vent stack. Replacement air must be provided by
means of ducts from the outside to the equipment
location or conditioned space. Under all conditions,
enough air must be provided to ensure there will not
be a negative pressure condition within the equip
ment room or space. 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 sideconnected returns should utilize an accessory
bottom closure, properly sealed.
Complete combustion requires approximately
10 cu ft of air for every 1000 Btu of gas fuel. In addi
tion, approximately 10 more cu ft of air is required
for draft hood dilution, and 10 more for ventilation
of the furnace enclosure. Thus, for eaeh 1000 Btu of
gas consumed, a total of 30 cu ft of air must be sup
plied. For a 100,000 Btuh gas furnace, this equals
3000 cu ft of air per hour (100 x 30) or 50 cu ft of air
per minute (3000 60). In the past, the infiltration
of outside air assumed in heat loss calculations (one
air change per hour) was assumed to be sufficient.
However, current eonstruction methods, utilizing
more insulation and vapor barriers, tighter fitting
and gasketed doors and windows or weatherstrip
ping, and the presence of fuel-burning fireplaces and
mechanical exhaust fans from kitchens, laundries,
and baths require the positive introduction of
outside air.
CAUTION; Combustion air must come from a
source that is not contaminated by halogens,
which include fluorides, chlorides, bromides,
and iodides. These elements are found in aerosol
sprays, detergents, bleaches, cleaning solvents,
salts, air fresheners, and other household prod
ucts. Vapors from these products are highly
corrosive to gas-fired furnaces, in even ex
tremely low concentrations—as low as 1 / 2 part
per million. When such contaminants are pre
sent, outside air mttft be ducted separately to
the furnace room.
Operation of exhaust fans, kitchen ventilation
systems, clothes dryers, or fireplaces may create
conditions requiring special attention to avoid un
satisfactory operation of installed gas furnaces.
Commonly used exhaust fans and range hoods
handle anywhere from 60 to 300 cfm (or more) and
gas or electric clothes dryers may remove more air.
With multiple use of such appliances common in
both old and new homes and apartments, special
provisions for positive introduction of outside air
are mandatory. This air requirement is several times
that required by the furnace, and must be replaced,
in addition to the air required by the furnace.
The requirements for combustion and ventilation
air depend upon whether the furnace is located in a
confined or unconfined space. An unconfined space
is defined as a space with a volume not less than
50 cu ft/1000 Btuh of the total input rating of all
appliances installed in that space. Rooms communi
cating directly with the space in which the appliances
are installed, thru openings not furnished with
doors, are considered a part of the unconfined space.
A confined space is defined as a space with a vol
ume less than 50 cu ft/1000 Btuh of the total input
ratings of all appliances installed in that space.
Furnaces in Confined Spaces (Typical Furnace
Closet)
ALL AIR FROM INSIDE BUILDINGS:
The confined space shall be provided with 2 per
manent 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 1 sq in. per 1000 Btuh of the total input
rating of all equipment in the enclosure, but not have
less than 100 sq inches. The openings must freely
communicate with interior areas served by the
furnace, either thru permanent openings or louvered
doors.
In addition, if building is of unusually tight con
struction, provide one permanent opening directly
communicating with outdoors. This opening shall
have a minimum free area of 1 sq in. per 5000 Btuh
of total input rating of all equipment in the en
closure. Ducts shall be used to convey makeup air
and shall be of the same cross-sectional area as the
free areas 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 the furnace is instafled 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 outdoors, as prescribed below.
ALL AIR FROM OUTDOORS:
The confined space shall be provided with 2 per
manent openings, one commencing within 12 in.
of the top and one commencing within 12 in. of the
i
/
A.
Page 3
RETURN OR
SUPPLY AIR
VENT TO ROOF
I I
I I I
I I I
T
12 IN MAX
I
D_L
■= I so IN.
~ PER 1000
BTUH*
INTERIOR
HEATED
SPACE
-6IN MIN
(FRONT)
ISO IN
# per 1000
HTBTUH*
I so IN. PER
2000 BTUH ^
i
RETURN OR
SUPPLY AIR
*MINIMUM OPENING SIZE IS 100 SO IN
J
-d
*-12 IN MAX
MAKEUP AIR
ISO IN
-PER 5000
BTUH FROM
OUTSIDE
(RETURN
AIR ONLY)
Fig. 1 — Upflow or Counterflow, Using Air
from Inside Building
bottom of the enclosure. These openings shall com
municate directly, or by ducts, with outdoors.
See Fig. 2.
a. When communicating with the outdoors thru
horizontal ducts, each opening shall have mini
mum free area of 1 sq in. per 2000 Btuh of total
input rating for 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 1 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 mini
mum dimension of rectangular air ducts shall not
be less than 3 inches.
Furnaces in Unconfined Spaces (Basements,
Large Equipment Rooms, etc.) — If the uncon
fined space is within a building of unusually tight
construction, air for combustion, ventilation, and
dilution of flue gases shall be obtained from out
doors or from spaces freely communicating with the
outdoors. A permanent opening, or openings,
having a total free area of not less than 1 sq. in. per
5000 Btuh of total input rating for all equipment
shall be provided. A duct may be used to convey
USE ANY OF THE FOLLOWING COMBINATIONS
OF OPENINGS: ABB CSD D&E
*MINIMUM OPENING SIZE IS 100 SO IN
Fig. 2 — Upflow or Counterflow. Using Air
from Outside Building
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 con
nected to the eold 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.
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
I
a “negative” pressure condition 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 I / 4-in. mesh.
If the free area thru 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-percent free area
and metal louvers and grilles will have 60- to 75percent free area. Louvers and grilles that provide
combustion and dilution air must be constructed so
they cannot be closed.
Page 4
GAS PIPING
The gas supply line should be a separate line
directly from the meter to the furnace, if possible.
Refer to Table 1 for recommended gas pipe sizing.
Do not use cast-iron or galvanized pipe.
located on the gas valve before the test. It is recom
mended that the ground joint union be cracked be
fore pressure testing.
After all connections have been made, purge the
lines and check for leakage.
Table 1 — Maximum Capacity of Gas Pipe*
NOMINAL
IRON PIPE
SIZE
(in.)
Z
’"3/4
1 T
1-1/4
1-1/2
*Cu ft of gas per hour for gas pressures 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 54-1980
INTERNAL
DIAMETER
(in.)
”^622~
0 824
1^049
1 380
1 6IO"
r''
1400
2100
LENGTH OF PIPE
(ft)
10_
20 30
120 97
360
250 200 170 151
68Í
465 375
950 770
1460 1180 990 900
40
320
660
50
82
73
285
580
Avoid low spots in long runs of pipe. It is best to
slope all pipe 1/4in. in 15ft 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
(omit the first 2 threads). Consult local supplier for
type of compound to be used. This pipe dope must
be resistant to the action of LP gas.
Install a sediment trap in the riser leading to the
furnace. This trap will collect dirt or condensate. It
can be installed by connecting a tee to the riser lead
ing to the furnace, so that the straight-thru 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 those requirements.
An accessible manual shutoff valve shall be in
stalled 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 upstream of the gas supply
connection to the furnace and downstream from
the manual shutoff valve.
Place a ground joint union between the gas con
trol manifold and the manual gas shutoff valve, or
use an approved flexible or semirigid conductor.
Support all piping with the appropriate straps,
hangers, etc. (one hanger every 10 ft minimum).
Piping should be pressure-tested before any
furnace, appliance, or shutoff valve is attached, in
accordance with the requirements of local and
national plumbing and gas codes.
If the pressure exceeds 0.5 psig, the gas supply
pipe must be disconnected from the furnace before
the pressure test. If the test pressure is equal to or
less than 0.5 psig, close the manual shutoff valve
WARNING: Never purge a fine into a combus
tion chamber. Never use matches, candles,
ñame or other sources of ignition for the pur
pose of checking leakage. Use a soap-and-water
solution to check for leakage.
- VENTING
Fig. 3 — Sediment Trap
Consult local codes. For additional information
refer to the “National Fuel Gas Code” (NFPA No.
54-1980 or ANSI Z223.1-1980). Unless the local
codes direct otherwise, the unit may be vented to a
permanent chimney, or to a listed type-B 1 gas vent.
All gas-fired furnaces are shipped with draft
diverters; therefore, connect the vent collar to the
chimney or gas vent to be used. The following
recommendations are made:
1. Select flue connection material that is satis
factory for installation and that meets require
ments of local codes.
2. Flue connection pipe must be at least as large as
outlet collar on furnace. No reduction in this
size is permissible in pipe run.
3. Run pipe as directly as possible with minimum
number of turns.
Maintain minimum of 1/4in. per linear ft up
4.
ward slope on all horizontal runs.
Rigidly support flue pipe with hangers and
straps to ensure that there will no movement
after installation.
Page 5
km
6. Insert the smallest flue conneetion pipe at the
highest level consistent with available headroom or clearance to combustible materials,
when 2 or more vent connectors enter a com
mon gas vent or chimney flue.
7. Extend flue connection pipe thru chimney wall,
flush with inner face of chimney liner and above
extreme bottom to avoid restriction.
WARNING; Never connect into a chimney
serving an open fireplace unless fireplace
opening is sealed off.
8.
No portion of the venting system shall extend
into or pass thru any circulating air duct or
plenum.
9.
Chimney or gas vent should extend at least 5 ft
above highest connected draft hood and should
extend high enough above roof of any neighbor
ing obstruction so that wind from any direction
will not create positive pressure in vicinity of a
chimney or gas vent outlet. Chimney or gas vent
should extend 3 ft higher than point of emer
gence thru roof, and at least 2 ft higher than any
object within radius of 10 feet. See Fig. 4.
A type-Bl gas vent shall terminate above the
10.
roof surface with a listed cap or roof assembly.
HEIGHT ABOVE ANY
ROOF SURFACE
WITHIN 10'
HORIZONTALLY
3 MIN GAS VENT
OR CHIMNEY
Tn
Fig. 4 — Chimney, Gas Vent Height
ELECTRICAL
3MIN GAS VENT
OR CHIMNEY
IMPORTANT: Before proceeding with the
electrical connections, make certain that
voltage, frequency, and phase correspond tp
that specified on the furnace rating plate. Also,
check to be sure that the service provided by the
utility is sufficient to handle the additional load
imposed by this equipment. Refer to the unit
rating plate for equipment electrical
requirements.
" The specific furnace installation instructions con
tain wiring diagrams that show the proper field highand low-voltage wiring. Make all connections in
accordance with the National Electrical Code and
any local codes or ordinances that might apply.
^ W.ARNING: The cabinet must have an unin-
terruoted or unbroken ground according to
National Electrical Code, ANSI/NFPA
70-1981, ANSI C1-19SI, or local codes to mini
mize personal injury if an electrical fault should
occur. This may consist of electrical wire or
conduit approved for electrical ground when
installed in accordance with existing electrical
codes. Do not use gas piping as an electrical
ground.
CAUTION; If manual disconnect switch is to be
mounted on the furnace, select a location where
drill or fastener will not contact electrical or
gas components.
NOTE; Use only copper wire between disconnect
switch and furnace. If aluminum wire is used be
tween service panel and disconnect switch, adhere
to the following recommendations.
When making aluminum conductor connections
to copper conductors or terminals, use only con
nectors that are UL approved (marked Al/Cu with
the UL symbol) for the application and wire size.
Do not reduce wire size to fit connector by cutting
off strands. Use properly sized connectors.
After insulation has been stripped from the
aluminum conductor, coat the conductor end with
corrosion inhibitor (Burndy Pentrox A or equiv
alent), and wire-brush the aluminum surface thru
the inhibitor.
CAUTION: Do not wire-brush connectors and
lugs. The plating will be broken.
After cleaning, recoat the aluminum conductor
with inhibitor, and make connection, then coat entire
connection. When it is suspected that the connection
will be exposed to moisture, it is very important to
cover the entire connection completely to prevent
an electrochemical action that will cause the con
nection to fail very quickly.
If aluminum conductors are to be used, the wire
size selected must have a current capacity not less
than that of the copper wire specified, and must not
create a voltage drop between the service panel
and the furnace in excess of 2% of the unit rated
voltage.
Check all electrical connections (both factory and
field) for tightness. This should also be done after
the unit has reached operating temperatures,
especially if aluminum conductors are used.
START-UP, ADJUSTMENT, AND
SAFETY CHECK
Pilot — Check to be sure that all connections have
been properly made, then proceed as follows;
Light the pilot, using the procedure outlined on
the Lighting Instruction Plate attached to the fur-
Page 6
nace. However, when lighting the pilot for the first
time, perform the following additional steps;
■ 1. If supply line was not purged before connecting
furnace, it will be full of air. It is recommended
that the ground joint union be cracked, and sup
ply line be allowed to purge until odor of gas is
detected. Never purge gas lines into combustion
chamber. Immediately upon detection of gas
odor, retighten the union. Allow 5 minutes to
elapse, then light pilot in accordance with in
structions on furnace.
2. Pilot flame should be soft blue in color.
a. For natural gas controls, flame should be long
enough to provide good impingement on ele
ment of pilot. Flame should extend above the
carryover ports of the burner.
b. For complete shutoff gas controls, flame
should surround tip of thermocouple element
of pilot and extend downward to include 3/8
to 1 / 2-in. of thermocouple. Flame must never
come in contact with any other part of ther
mocouple or its lead wire. Flame lies under
carryover port of burner and merges with
carryover flame.
3. Pilot adjusting screw is located on main gas valve
or pilot shutoff valve.
a. Remove capscrew; turn pilot gas full on and
turn adjusting screw until desired appearance
is obtained.
b. Replace capscrew.
4. For natural gas controls, check the pilot oper
ation as follows: Attach a low-voltage test light
to electrical leads of gas valve. With thermostat
set above room temperature, shut off gas supply
to burners and pilot with main manual shutoff
valve. If test light goes out within 45 seconds,
pilot is functioning properly. If light does not go
out within 60 seconds, replace pilot.
5. The 100% safety control can be easily checked
by unscrewing pilot thermocouple lead from gas
valve. Pilot and main burner gas should shut off
— no gas should flow thru valve. After valve is
checked and found to operate satisfactorily,
reconnect thermocouple to gas valve to fingertight position. Then tighten 1/4 turn with a
wrench. Relight pilot, following lighting instruc
tions on furnace.
Burners — Light main burners using procedure
contained on Lighting Instruction Plate attached to
furnace.
Gas Input — Determine the gas input as follows:
NATURAL GAS
1. Turn off all other gas appliances and pilots.
2. Measure time (in seconds) for gas meter test dial
to complete one revolution.
3. Refer to Table 2 for cu ft of gas per hour.
Table 2 — Gas Rate (Cubic Feet Per Hour)
SECONDS
FOR ONE
REVOLUTION
10
11
12 300
13 277 555
14
15
16
17 212
18
19 189
20 180
21 171 343 857
22
23
24 150 300
25
26
27 133
28
29 124
30 120
31 116
32 113
33
34 106
35
36
37 97
38
39
40
41 88 176
42
43
44 82
45
46
47
48
49
Multiply cu ft per hour times heating value of
4.
SIZE OF
TEST DIAL
2 5
1
cu ft cu ft
360 720 1800
327 655
600
257 514
480 1200
240
225 450
424 1059
200 400 1000
379 947
360 900
164 327 818
157 313
144 288 720
277 692
138
267 667
129 257 643
248
240 600
232 581
225
109 218
212 529
206
103
100 200 500
195 486
189
95
92 185 462
90 180 450
86 172
84 167 419
164
80 160 400
157 391
78
76 153 383
75 150 375
73 147
SECONDS
FOR ONE
REVOLUTION
cu ft
1636 51
1500
1385
1286 54
1125 56
783
750
621 78
563
545 86
514 90 40
474 96 38
439
429
409
367
50
52 69 138
53 68
55
57 63 126
58
59
60 60"^ 120
62 58 116
64 56 112 281
66
68
70
72
74
76
80
82
84
88
92 39 78
94 38
98
100
102
104 35 69
106
108
110 33
112
116
120
SIZE OF
TEST DIAL
»»"—
---
----
,
1
2 5
CU ft cu ft cu ft
72 144 360
71 141 355
136 340
67 133 333
65 131 327
64
129
62
124
61 122 305
54
109
53 106 265
51 103
50 100
48 97 243
47 95
46 92 231
45 90
44
88
43 86
42 84 209
41 82 205
80
76
75
74
37
36 72
71 178
35
34 68
67 167
33
65
32 64 161
31 62
30 60
J
gas (Btu/ cu ft). Obtain heating value of gas from
local gas utility.
Example:
Btu/cu ft X cu ft = Btuh heating input
Time for one revolution of 2 cu ft dial
= 72 seconds
Heat value of gas = 1070 Btuh/cu ft
100 X 1070 = 107,000 Btuh input
Measured gas input should not exceed gas
^ 5.
input shown on unit rating plate.
6. To adjust input rate, remove cap that conceals
regulator adjustment. Turn adjusting screw
counterclockwise (out) to decrease input. When
adjusting, DO NOT change manifold pressure
more than 0.3 in. wg. Any major adjustment
should be made by changing main burner
orifices.
LP (PROPANE) GAS — These units are equipped
with pressure regulators. Burner orifices are sized to
346
321
316
310
300
290
273
257
250
237
225
220
214
200
196
192
188
184
180
173
170
164
155
150
Page 7
give rated input at a manifold pressure of 10.5 in. wg.
Check manifold pressure and, if necessary, adjust
pressure.
HIGH ALTITUDE — Ratings are approved for
altitudes to 2000 ft for all gases. Ratings for altitudes
over 2000 ft are 4% less for each 1000 ft above sea
level.
Adjust Main Burner Flame — The main burner
flame should be clear blue, almost transparent,
with a well-defined inner cone. If there is too much
primary air, the flame will be well defined, but
with a tendency to float or lift off the burner ports.
See Fig. 5.
Limit Control Safety Check — This control shuts
off the gas and energizes the blower motor if the
furnace becomes overheated.
The recommended method of checking the limit
control is to gradually block off the return air after
the furnace has been operating for a period of at
least 5 minutes. As soon as the limit has proven
safe, the return air opening should be unblocked to
permit normal air circulation. By using this method
to check the limit control, it can be established that
the limit is functioning properly and will be fail-safe
if there is a motor failure.
FURNACE LOCATION WITH RESPECT
TO COOLING EQUIPMENT
The cooling coil must be installed parallel with
or on the downstream side of the furnace to avoid
condensation in the heating element. When installed
parallel with a furnace, dampers or other means
used to control the flow of air must prevent chilled
air from entering the unit. If the dampers are
manually operated, they must be equipped with
means to prevent operation of either unit unless the
damper is in the full-heat or full-cool position, i
1. Allow unit to operate 5 minutes.
2. When burners are equipped with primary air
adjustment, adjust each burner by closing air
adjustment device until slight yellow tip appears
on flame; then open, just enough to clear yellow
from flame.
Temperature Rise — The unit is to be adjusted
within the temperature rise range specified on the
rating plate. Determine the air temperature rise as
follows:
1. Place duct thermometers in return and supply
ducts as near furnace as possible. Be sure ther
mometers do not “see” heat element so that
radiant heat will not affect thermometer read
ings. This is particularly important with straightrun ducts.
2. When thermometers stabilize, subtract return air
temperature from supply air temperature to
determine air temperature rise.
3. Adjust air temperature rise by adjusting blower
speed. Increase blower speed to reduce tempera
ture rise. Decrease blower speed to raise tempera
ture rise.
^ SPECIAL LOCATIONS
A gas-fired furnace installed in a residential
garage should be installed so the burners and igni
tion source are located not less than 18 in. above
the floor and the furnace is located or protected to
avoid physical damage by vehicles.
When furnaces are installed in public garages, air
plane hangars, or other buildings having hazardous
atmospheres, the unit should be installed in accord
ance with the recommended good practice require
ments of the National Board of Fire Underwriters.
#
Page 8
#
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book 1
Tab
6a
Form58-9XA Supersedes58-7XA PrintedinUSA 3-82 PC 101
Catalog No 515-802
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