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The gas valve is factory set and should not require adjust-
ment. All gas valves are factory regulated.
Manifold Adjustment Procedure:
1 - Connect test gauge to manifold pressure tap
(FIGURE 19 and FIGURE 20) on gas valve.
2 - Ignite unit on low fire and let run for 5 minutes to
allow for steady state conditions.
3 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
TABLE 19.
4 - If necessary, make adjustments. FIGURE 19 and
FIGURE 20 show location of high fire and low fire
adjustment screw.
5 - Repeat steps 2, 3 and 4 on high fire.
6 - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
replace pressure tap plug.
7 - Start unit and perform leak check. Seal leaks if
found.
F- Proper Gas Flow (Approximate)
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures
a more accurate time.) Divide by two and compare to time
in TABLE 17. If manifold pressure matches TABLE 19 and
rate is incorrect, check gas orifices for proper size and
restriction.
NOTE- To obtain accurate reading, shut off all other gas
appliances connected to meter.
G- Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. See sections E- and F-. Take combustion sam-
ple beyond the flue outlet and compare to TABLE 18. The
maximum carbon monoxide reading should not exceed
100 ppm
GAS METERING CLOCKING CHART
Natural 1000 btu/
SL280
Unit
1 cu ft
dial
-045
80
-070
55
-090
41
-110
33
-135
27
For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
Firing Rate
High Fire
Low Fire
The carbon monoxide reading should not exceed 100 ppm.
H- High Altitude
The manifold pressure, gas orifice and pressure switch
may require adjustment or replacement to ensure proper
operation at higher altitudes. See TABLE 19 for manifold
pressures and TABLE 20, TABLE 21 and TABLE 22for
pressure switch and gas conversion kits.
Page 49
TABLE 17
LP 2500 btu cu/cu ft
cu ft
Seconds For One Revolution
2 cu fr
1 cu ft
dial
Dial
160
200
110
136
82
102
66
82
54
68
IMPORTANT
TABLE 18
CO2% For Nat
CO2% For L.P.
6.8 - 7.4
4.2 - 5.7
2 cu ft
Dial
400
272
204
164
136
7.5 - 9.0
5.0 - 6.0
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