b. Check gas input rate by clocking gas meter.(1.) Obtain average yearly heat value for local gassupply.(2.) Check and verify orifice size in furnace. NEVERASSUME THE ORIFICE SIZE. ALWAYSCHECK AND VERIFY.CAUTION: DO NOT redrill burner orifices. Improperdrilling (burrs, out of round, etc.) can cause excessiveburner operating noise and misdirection of burner flames.This could result in flame impingement on burners andheat exchanger surfaces, leading to potential failures.(3.) Turn off all other gas appliances and pilots.(4.) Start furnace and let run for 3 minutes.(5.) Measure time (in sec) for gas meter to complete 1revolution.(6.) Refer to Table 7 for cu ft of gas per hr.(7.) Multiply gas rate (cu ft/hr) by heating value (Btu/cuft).EXAMPLE:Btu heating input = Btu/cu ft X cu ft/hrHeating value of gas = 1070 Btu/cu ftTime for 1 revolution of 2 cu ft dial = 72 secGas rate = 100 X 1070 = 107,000 Btuh(8.) Measured gas input should not exceed gas input onunit rating plate.(9.) Proceed to item c to adjust manifold pressure.c. Adjust gas input.(1.) Remove regulator adjustment seal cap. (See Fig.12.)(2.) Turn adjusting screw counterclockwise to decreaseinput. Turn screw clockwise to increase input. DONOT set manifold pressure less than 3.2-in. wc ormore than 3.8-in. wc for natural gas. Make anymajor adjustments by changing main burner ori-fices.TABLE 6—MODEL 395CAV ORIFICE SIZE AND MANIFOLD PRESSURE FOR CORRECT INPUT RATE(Tabulated Data Based on Altitude Up to 2000 Ft and 22,000 Btuh Per Burner)GAS
HEAT
VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.56 0.58 0.60 0.62 0.64 0.66 0.68 0.70 0.72
Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press. Orf
No. Mnfld
Press.
860 41
42
—
3.2
3.6
—
41
42
—
3.3
3.7
—
41
42
40
3.4
3.8
3.2
41
40
—
3.5
3.3
—
41
39
40
3.7
3.2
3.4
41
39
40
3.8
3.3
3.5
39
40
—
3.4
3.6
—
38
39
40
3.2
3.5
3.7
38
39
40
3.3
3.6
3.8
875 42
—
—
3.4
—
—
41
42
—
3.2
3.6
—
41
42
—
3.3
3.7
—
41
42
40
3.4
3.8
3.2
41
40
—
3.5
3.3
—
41
39
40
3.6
3.2
3.4
41
39
40
3.8
3.3
3.5
39
40
—
3.3
3.6
—
38
39
40
3.2
3.4
3.7
890 42
—
—
3.3
—
—
42
—
—
3.4
—
—
41
42
—
3.2
3.6
—
41
42
—
3.3
3.7
—
41
42
—
3.4
3.8
—
41
40
—
3.5
3.2
—
41
40
—
3.6
3.3
—
41
39
40
3.7
3.2
3.4
41
39
40
3.8
3.3
3.5
905 42
—
—
3.2
—
—
42
—
—
3.3
—
—
42
—
—
3.4
—
—
41
42
—
3.2
3.6
—
41
42
—
3.3
3.7
—
41
42
—
3.4
3.8
—
41
40
—
3.5
3.2
—
41
40
—
3.6
3.3
—
41
39
40
3.7
3.2
3.4
920 43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—41
42 3.2
3.5 41
42 3.3
3.7 41
42 3.4
3.8 41
40 3.5
3.2 41
40 3.6
3.3
935 43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—41
42 3.2
3.5 41
42 3.3
3.7 41
42 3.4
3.8 41
40 3.5
3.2
950 43
—3.6
—43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—41
42 3.2
3.5 41
42 3.3
3.6 41
42 3.4
3.7
965 43
—3.4
—43
—3.6
—43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—41
42 3.2
3.5 41
42 3.3
3.6
980 44
43 3.8
3.3 42
—3.5
—43
—3.6
—43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—41
42 3.2
3.5
995 44
43 3.7
3.2 44
43 3.8
3.4 43
—3.5
—43
—3.6
—43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—42
—3.4
—
1010 44
—3.6
—44
43 3.7
3.3 44
43 3.8
3.4 43
—3.5
—43
—3.6
—43
—3.7
—43
—3.8
—42
—3.2
—42
—3.3
—
1025 44
—3.5
—44
43 3.6
3.2 44
43 3.7
3.3 43
—3.4
—43
—3.5
—43
—3.6
—43
—3.7
—43
—3.8
—43
—3.2
—
1040 44
—3.4
—44
—3.5
—44
43 3.6
3.2 44
43 3.7
3.3 43
—3.4
—43
—3.5
—43
—3.6
—43
—3.7
—43
—3.8
—
1055 44
—3.3
—44
—3.4
—44
—3.5
—44
43 3.6
3.2 44
43 3.8
3.3 43
—3.4
—43
—3.5
—43
—3.6
—43
—3.7
—
1070 44
—3.2
—44
—3.3
—44
—3.4
—44
—3.5
—44
43 3.7
3.2 44
43 3.8
3.3 43
—3.4
—43
—3.5
—43
—3.6
—
1085 45
—3.8
—44
—3.2
—44
—3.3
—44
—3.4
—44
—3.6
—44
43 3.7
2.3 44
43 3.8
3.3 43
—3.4
—43
—3.5
—
1100 45
—3.7
—45
—3.8
3.4 44
—3.2
—44
—3.4
—44
—3.5
—44
—3.6
—44
43 3.7
3.2 44
43 3.8
3.3 43
—3.4
—
—12—