Table of Contents
Advertisement
ADJUSTING OR CHECKING
FURNACE INPUT
NATURAL GAS:
The maximum gas supply pressure to
the furnace should be 10.5" W.C. for
natural gas. The minimum gas supply
pressure for purposes of input
adjustment to the furnace should be 5"
W.C.
A properly calibrated manometer or
gauge is required for accurate gas
pressure readings.
The manifold pressure should be set at
3.5" W.C. for natural gas. Only small
variations in the gas flow should be
made by means of the pressure
regulator adjustment.
To adjust the pressure regulator:
1. Remove the regulator cap.
2. Turn the adjustment screw clockwise
to increase pressure or
counterclockwise to decrease
pressure.
3. Replace the regulator cap securely.
LP GAS:
Furnaces for use on LP gas, the LP gas
supply pressure must be set between
11.0" and 13.0" W.C. by means of the
tank or branch supply regulators. The
furnace manifold pressure should be set
at 10" W.C. at the gas control valve. For
elevations up to 8,000 feet, rating plate
input ratings apply. For high altitudes
(elevations 8,000 and over) and for any
necessary major changes in the gas
flow rate the orifice spud must be
changed.
TO CHANGE ORIFICE SPUDS:
1. Shut off the manual main gas valve
and remove the gas manifold.
2. Replace the orifice spuds.
3. Reassemble in reverse order.
4. Turn the gas supply back on and
check for proper operation and
manifold pressure.
Check of input is important to prevent
over firing of the furnace beyond its
design-rated input. NEVER SET INPUT
ABOVE THAT SHOWN ON THE
RATING PLATE.
TO CHECK FURNACE INPUT:
1. Make certain that all other gas
appliances are shut off, with the
exception of pilot burners.
2. Start the furnace
3. Time the meter to measure the time
required to burn one cubic foot of
gas.
4. Use Table 6 to determine input rate.
ALTERNATE METHOD FOR
CANADIAN HIGH-ALTITUDE
DERATE
In Canada, unless an orifice change is
specifically mandated by local codes, an
alternate method of altitude deration
through a reduction in manifold pressure
is acceptable as described in Table 5.
This information is based on a heating
TABLE 5
ALTERNATE METHOD FOR CANADIAN HIGH-ALTITUDE DERATE
NATURAL GAS
ORIFICE
ALTITUDE
INPUT
OUTPUT
SIZE
50,000
40,000
75,000
60,000
0' - 2000'
100,000
80,000
#42
125,000
100,000
150,000
120,000
45,000
36,000
67,500
54,000
2001' - 4500'
90,000
72,000
#42
112,500
90,000
135,000
108,000
FIGURE 14
MANIFOLD PRESSURE-CHANGE LABEL
THE MANIFOLD PRESSURE OF THIS APPLIANCE HAS
BEEN FIELD ADJUSTED TO OBTAIN THE CORRECT
INPUT RATING FOR INSTALLATION AT ALTITUDES
BETWEEN 2,000 FEET AND 4,500 FEET ELEVATION.
LA PRESSION DU DISTRIBUTEUR D'ALIMENTATION
DE CET APPAREIL A ÉTÉ AJUSTÉ SUR LES LIEUX AFIN
D'OBTENIR LA BONNE PUISSANCE D'ENTRÉE POUR
UNE INSTALLATION ENTRE 2000 ET 4500 PIEDS
TABLE 6
METER TIME IN MINUTES AND SECONDS FOR NORMAL
INPUT RATING OF FURNACES EQUIPPED FOR NATURAL OR LP GAS
METER
INPUT
SIZE
BTU/HR
CU. FT.
MIN. SEC. MIN. SEC. MIN. SEC. MIN. SEC. MIN. SEC.
ONE
50,000
TEN
ONE
75,000
TEN
ONE
100,000
TEN
ONE
125,000
TEN
ONE
150,000
TEN
Heating Value of Gas (BTU/Ft
Input BTU/HR =
Time in Seconds (for 1 cu.ft.) of Gas
value of 1000 BTU per cubic feet of
natural gas, and 2500 BTU per cubic
feet of LP gas.
IMPORTANT: Actual input rates must
be measured onsite with manifold
pressure adjustment to ensure that an
actual 10% reduction in input rate is
achieved.
Once this field adjustment has been
made, the label shown in Figure 14
rmust be affixed in a conspicuous
location on the front of the furnace
cabinet.
NOTE: This label is supplied in the
information packet shipped with each
furnace.
MANIFOLD
ALTITUDE
INPUT
PRESSURE
50,000
75,000
3.5" W.C.
0' - 2000'
100,000
125,000
150,000
45,000
67,500
2.9" W.C.
2001' - 4500'
90,000
112,500
135,000
D'ALTITUDE.
92-24399-01-01
HEATING VALUE OF GAS BTU PER CU. FT.
900
1000
1040
1100
1
5
1
12
1
15
1
10
50
12
00
12
30
13
0
44
0
48
0
50
0
7
12
8
0
8
19
8
0
33
0
36
0
38
0
5
24
6
0
6
15
6
0
26
0
29
0
30
0
4
19
4
48
5
0
5
0
31
0
24
0
25
0
3
36
4
0
4
10
4
3
) x 3600 x correction factor
LP GAS
ORIFICE
MANIFOLD
OUTPUT
SIZE
PRESSURE
40,000
60,000
80,000
#54
10" W.C.
100,000
120,000
36,000
54,000
72,000
#54
8.1" W.C.
90,000
108,000
2500
18
3
20
12
30
00
53
2
0
48
20
0
40
1
30
36
15
0
32
1
12
17
12
0
26
1
0
20
10
0
19
Hide quick links:
Advertisement
Table of Contents
Troubleshooting
