18-CD19D8-18
31
Installer’s Guide
GAS PIPING
The upflow/horizontal furnace is shipped standard for left
side installation of gas piping. A knockout is provided on the
right side for an alternate gas piping arrangement. See Figure
49.
The installation of piping shall be in accordance with piping
codes and the regulations of the local gas company. Pipe joint
compound must be resistant to the chemical reaction with
liquefied petroleum gases.
Refer to piping Table 13, for delivery sizes. Connect gas
supply to the unit, using a ground joint union and a manual
shut-off valve as shown in Figures 49 & 50. National codes
require a condensation drip leg to be installed ahead of the
controls as shown in Figures 49-51.
▲
CAUTION
!
Use a backup wrench on the gas valve when installing gas
piping to prevent damage to the gas valve and manifold
assembly.
The furnace and its individual shut-off valve must be discon-
nected from the gas supply piping system during any pressure
testing of that system at test pressures in excess of 1/2 psig
(3.5 kPa).
The furnace must be isolated from the gas supply piping by
closing its individual manual shut-off valve during any
pressure testing of the gas supply piping system at test
pressures equal to or less than 1/2 psig (3.5 kPa).
NOTE:
Maximum pressure to the gas valve for natural gas is 13.8"
W.C. Minimum pressure is 5.0" W.C. Maximum pressure to
the gas valve for propane is 13.8" W.C. Minimum pressure
is 11.0" W.C.
All gas fittings must be checked for leaks using a soapy
solution before lighting the furnace.
DO NOT CHECK
WITH AN OPEN FLAME!
TABLE 13 NATURAL GAS ONLY
TABLE OF CUBIC FEET PER HOUR OF GAS
FOR VARIOUS PIPE SIZES AND LENGTHS
PIPE
SIZE
LENGTH OF PIPE
10
20
30
40
50
60
70
1/2
132
92
73
63
56
50
46
3/4
278
190
152
130
115
105
96
1
520
350
285
245
215
195
180
1-1/4
1050
730
590
520
440
400
370
This table is based on pressure drop of 0.3 inch W.C. and 0.6 SP.GR. gas
TABLE 14 ORIFICE SIZES
INPUT
RATING
BTUH
NUMBER
OF
BURNERS
MAIN BURNER ORIFICE
DRILL SIZE
NAT. GAS
LP GAS
60,000
80,000
100,000
120,000
3
4
5
6
45
45
45
45
56
56
56
56
COMBUSTION AND INPUT CHECK
(See also High Altitude Derate)
1. Make sure all gas appliances are off except the furnace.
2. Clock the gas meter with the furnace operating (deter-
mine the dial rating of the meter) for one revolution.
3. Match the “Sec” column in the gas flow (in cfh) Table 15
with the time clocked.
4. Read the “Flow” column opposite the number of seconds
clocked.
5. Use the following factors if necessary:
For 1 Cu. Ft. Dial Gas Flow CFH =
Chart Flow Reading ÷ 2
For 1/2 Cu Ft. Dial Gas Flow CFH =
Chart Flow Reading ÷ 4
For 5 Cu. Ft. Dial Gas Flow CFH =
10X Chart Flow Reading ÷ 4
▲
CAUTION:
Return all tubing, caps, and/or plugs to original positions when pressure checks are completed.
W
