18-CD19D5-25
33
Installer’s Guide
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
40,000
60,000
80,000
100,000
120,000
2
3
4
5
6
45
45
45
45
45
56
56
56
56
56
COMBUSTION AND INPUT CHECK
1. Make sure all gas appliances are off except the fur-
nace.
2. Clock the gas meter with the furnace operating (de-
termine the dial rating of the meter) for one revolu-
tion.
3. Match the “Sec” column in the gas flow (in cfh)
Table 16 with the time clocked.
4. Read the “Flow” column opposite the number of sec-
onds 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
6. Multiply the final figure by the heating value of the
gas obtained from the utility company and compare
to the nameplate rating. This must not exceed the
nameplate rating.
Gas Valve Adjustment
Changes can be made by adjusting the manifold pres-
sure (See Table 15), or changing orifices (orifice
change may not always be required). To adjust the
manifold pressure:
1. Turn off all electrical power to the system.
2. Attach a manifold pressure gauge with flexible
tubing to the outlet pressure boss marked “OUT P”
on White-Rodgers gas valve model 36G or 36J. See
Figure 57 for White-Rodgers gas valve model 36J.
See Figure 56 for White-Rodgers gas valve model
36G.
3. Loosen (Do Not remove) the pressure tap test set
screw one turn with 3/32" hex wrench.
a. The pressure tap adjustment kit (KIT07611)
contains a 3/32" hex wrence, a 5/16" hose and a
connector and can be ordered through Global
Parts.
4. Turn on system power and energize valve.
5. Adjust gas heat by removing the adjustment
regulator cover screw.
a. To increase outlet pressure, turn the regulator
adjust screw clockwise.
b. To decrease outlet pressure, turn the regulator
adjust screw counterclockwise.
c. Adjust regulator until pressure shown on mano-
meter matches the pressure specified in Table
15.
1. The input of no more than nameplate rating
and no less than 93% of the nameplate rating,
unless the unit is derated for high altitude.
HORIZONTAL FURNACE GAS PIPING MAY BE FROM EITHER SIDE (UPFLOW SHOWN)
AUTOMATIC GAS VALVE
WITH MANUAL SHUTOFF
MAIN MANUAL
SHUTOFF VALVE
GROUND
UNION JOINT
DRIP
LEG
MAIN MANUAL
SHUTOFF VALVE
GROUND UNION JOINT
DRIP
LEG
AUTOMATIC GAS VALVE
WITH MANUAL SHUTOFF
E
