IMPORTANT:
Check the rating plate to make certain the unit is
equipped to burn the type of gas supplied. Care should be taken
after installation of this equipment that the gas control valve not
be subjected to high gas supply line pressure.
In making gas connections, avoid strains as they may cause
noise and damage the controls. A backup wrench is required to
be used on the valve to avoid damage.
The capacities of gas pipe of different diameters and lengths in
cu. ft. per hr. with pressure drop of 0.3 in. and specific gravity
of 0.60 (natural gas) are shown in Table 2.
After determining the pipe length, select the pipe size which
will provide the minimum cubic feet per hour required for the
gas input rating of the furnace. By formula:
Gas Input of Furnace
(BTU/HR)
Cu. Ft. Per Hr. Required
=
Heating Value of Gas
(BTU/FT
3
)
The gas input of the furnace is marked on the furnace rating
plate. The heating value of the gas (BTU/FT
3
) may be
determined by consulting the local natural gas utility or the
L.P. gas supplier.
LP Conversion
Convert the valve to use liquefied petroleum (LP) gas by
replacing the pressure regulator spring with the conversion kit
spring. This LP kit spring allows the regulator to maintain the
proper manifold pressure for LP gas. The correct burner LP
orifices are included in the kit. See Figure 13.
IMPORTANT:
To remove the gas valve, remove the four screws
securing the manifold pipe to the burner tray. Remove the manifold
pipe with gas valve attached. See Figure 14.
NOTE:
Order the correct LP conversion kit from the furnace
manufacturer.
See Conversion Kit Index shipped with unit for
proper LP kit number. Furnace conversion to LP gas must
be performed by a qualified technician.
Adjusting or Checking Furnace Input
– Natural Gas Line Pressure 5
ⴖ
- 10.5
ⴖ
W.C.
– LP Gas Line Pressure 11
ⴖ
- 13
ⴖ
W.C.
– Natural Gas Manifold Pressure 3.5
ⴖ
W.C
– LP Gas Manifold Pressure - 10
ⴖ
W.C.
Supply and manifold pressure taps are located on the gas valve
body 1/8
ⴖ
N.P.T. and on the manifold.
Use a properly calibrated manometer gauge for accurate gas
pressure readings.
Only small variations in the gas flow should be made by
means of the pressure regulator adjustment. Furnaces
functioning on LP gas must be set by means of the tank or
branch supply regulators. The furnace manifold pressure
should be set at 10
ⴖ
W.C. at the gas control valve.
To adjust the pressure regulator, remove the regulator cap and
turn the adjustment screw clockwise to increase pressure or
counterclockwise to decrease pressure.
Then replace the
regulator cap securely.
Any necessary major changes in the gas flow rate should be
made by changing the size of the burner orifices. To change
orifice spuds, shut off the manual main gas valve and remove
the gas manifold.
For elevations up to 2,000 feet, rating plate input ratings
apply. For high altitudes (elevations over 2,000 ft.), see
conversion kit index 92-21519-XX for derating and orifice
spud sizes.
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. Use the following table or formula to determine
input rate.
Heating Value of Gas
(BTU/Cu. Ft.) x 3600
Cu. Ft. Per Hr. Required =
Time in Seconds
(for 1 Cu. Ft.) of Gas
Start the furnace and measure the time required to burn one
cubic foot of gas. Prior to checking the furnace input, make
certain that all other gas units are shut off, with the exception
of pilot burners. Time the meter with only the furnace in
operation.
12
IM 861
Nominal
Iron Pipe
Size,
Inches
Equivalent Length of Pipe, Feet
10
20
30
40
50
60
70
80
1
⁄
2
132
92
73
63
56
50
46
43
3
⁄
4
278
190
152
130
115
105
96
90
1
520
350
285
245
215
195
180
170
1
1
⁄
4
1,050
730
590
500
440
400
370
350
1
1
⁄
2
1,600 1,100
890
760
670
610
560
530
Table 2: Gas Pipe Capacity Table (Cu. Ft./Hr.)
This unit is equipped at the factory for use on natural gas
only. Conversion to LP gas requires a special kit supplied by
the distributor or manufacturer. Mailing addresses are listed
on the furnace rating plate, parts list and warranty. Failure to
use the proper conversion kit can cause fire, carbon
monoxide poisoning, explosion, personal injury, property
damage or death.
▲
▲
DANGER
!
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied
petroleum gases (at 11 inches water column inlet pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
Table 3: LP Gas Pipe Capacity Table (Cu. Ft./Hr.)
Nominal
Iron Pipe
Size, Inches 10
20
30
40
50
60
70
80
90
100
125
150
275
189
152
129
114
103
96
89
83
78
69
63
567
393
315
267
237
217
196
182
173
162
146
132
1,071
732
590
504
448
409
378
346
322
307
275
252
2,205 1,496 1,212 1,039
913
834
771
724
677
630
567
511
3,307 2,299 1,858 1,559 1,417 1,275 1,181 1,086 1,023
976
866
787
6,221 4,331 3,465 2,992 2,646 2,394 2,205 2,047 1,921 1,811 1,606 1,496
1/2
3/4
1
1-1/4
1-1/2
2
Length of Pipe, Feet
Example (LP): Input BTU requirement of unit, 150,000
Equivalent length of pipe, 60 ft. = 3/4
ⴖ
IPS required.
