30 18-CD35D1-1
INSTALLER’S GUIDE
TABLE 15
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 16
ORIFICE SIZES
MODEL
INPUT
RATING
BTUH
NUMBER
OF
BURNERS
MAIN BURNER
ORIFICE
DRILL SIZE
NAT.
GAS
LP GAS
M951P040BU24AA
40,000
2
45
56
M951P060BU36AA
60,000
3
45
56
M951P080BU42AA
80,000
4
45
56
M951P100CU48AA
M951P100DU60AA
97,000
5
45
56
M951P120DU60AA
110,000
6
45
56
M951P040BD24AA
40,000
2
45
56
M951P065BD42AA
60,000
4
48
56
M951P085CD48AA
80,000
5
48
56
M951P110DD60AA
110,000
6
48
56
COMBUSTION AND INPUT CHECK
1. Make sure all gas appliances are off except the furnace.
2. Clock the gas meter with the furnace operating (determine
the dial rating of the meter) for one revolution.
3. Match the “Sec” column in the gas flow (in CFH) Table
18 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
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 pressure (See
Table 17), 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 36J. See Figure 58 for White-
Rodgers gas valve model 36J.
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 wrench, a 5/16" hose and a connector and
can be ordered through the manufacturer.
HORIZONTAL FURNACE GAS PIPING MAY BE FROM EITHER SIDE (UPFLOW SHOWN)
GROUND UNION JOINT
DRIP
LEG
AUTOMATIC GAS VALVE WITH
MANUAL SHUTOFF
MAIN MANUAL
SHUTOFF VALVE
GROUND
UNION JOINT
DRIP
LEG
MAIN MANUAL
SHUTOFF VALVE
AUTOMATIC GAS VALVE
WITH MANUAL SHUTOFF
R
