Page 15
Pub. No. 41-5010-20
Installation Instructions
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
START-UP AND ADJUSTMENT
PRELIMINARY INSPECTIONS
With gas and electrical power “OFF”
1. Duct connections are properly sealed
2. Filters are in place
3. Venting is properly assembled
4. Blower door is in place
Turn main gas valve within the unit to the “
OFF
” position. Turn
the external gas shut-off valve to “ON”. Purge the air from the gas
lines. After purging, check all gas connections for leaks with a
soapy solution —
DO NOT CHECK WITH AN OPEN FLAME.
Allow 5 minutes for any gas that might have escaped to dissipate.
LP Gas, being heavier than air, may require forced ventilation.
Turn the knob on the gas valve in the unit to the “ON” position.
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 12 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.
7. Changes can be made by adjusting the manifold pressure or
changing orifices (orifice change may not always be required). To
adjust the manifold pressure:
a. Turn off all electrical power to the system.
b. Attach a manifold pressure gauge to the outlet pres-
sure tap marked “OUT PRESS TAP” on White-Rodgers
gas valve model 36F or boss marked “OUT P” on
White-Rodgers gas valve model 36G. (See Figure 18 for
White-Rodgers gas valve model 36F and Figure 17 for
White-Rodgers gas valve model 36G.) For the gas valve
model 36F, measurement requires removal of the plug
and installation of a barbed fitting. Attach flexible tub-
ing and a manometer to the barbed fitting.
For the gas valve model 36G, do not remove the pres-
sure tap test screw. Using a 3/32" hex wrench, loosen
the pressure tap test screw one turn and install 5/16"
flexible tubing and a manometer directly onto the outlet
pressure boss.
c. Turn on system power and energize valve.
d. Remove the regulator adjustment screw cap on the gas
valve for manifold pressure adjustment.
e. Turn the adjustment nut clockwise to increase the gas
flow rate, and counterclockwise to decrease the gas flow
rate using a 3/32" hex wench.
f. The final manifold pressure setting shall be 3.5" W.C.
with an input of no more than nameplate rating and no
TABLE 9
TABLE 10
TABLE 11
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
140,000
2
3
4
5
6
7
45
45
45
45
45
45
56
56
56
56
56
56
PART NUMBERS FOR REPLACEMENT ORIFICES
DRILL
SIZE
PART
NUMBER
DRILL
SIZE
PART
NUMBER
44
45
46
47
48
49
50
ORF00501
ORF00644
ORF00909
ORF00910
ORF01099
ORF00503
ORF00493
54
55
56
57
58
59
ORF00555
ORF00693
ORF00907
ORF00908
ORF01338
ORF01339
less than 93% of the nameplate rating, unless the unit
is derated for high altitude.
g. Replace the regulator adjustment screw cap and tighten
securely.
h. Turn off all electrical power to the system.
i. Remove the manometer and flexible tubing. Remove the
barbed fitting and replace the plug or tighten the pres-
sure test screw.
j. Turn on electrical power to the system and energize
valve.
k. Using a leak detection solution or soap suds, check for
leaks at plug or pressure boss screw.
▲
CAUTION
!
Replace and/or tighten all plugs removed or loosened when
adjusting gas pressure. Leak check the fittings before
placing the furnace into regular service. Failure to follow this
warning could result in fire, explosion, or property damage.
For LP gases, the final manifold pressure setting shall be 10.5"
W.C. with an input of no more than the nameplate rating and no
less than 93% of the nameplate rating, unless the unit is derated
for altitude.
Table 10 lists the main burner orifices shipped with the furnace.
If a change of orifices is required to correct the input rate, refer to
Table 11.
