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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 18 below. If manifold pressure matches TABLE
20 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.
TABLE 18
GAS METERING CLOCKING CHART
SL280
Unit
Natural 1000 btu/cu ft
LP 2500 btu cu/cu ft
Seconds For One Revolution
1 cu ft dial 2 cu fr dial 1 cu ft Dial 2 cu ft Dial
-070
55
110
136
272
-090
41
82
102
204
-110
33
66
82
164
IMPORTANT
.For safety, shut unit off and remove manometer as soon
as an accurate reading has been obtained. Take care to
replace pressure tap plug.
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 sample beyond
the flue outlet and compare to the table below. The max-
imum carbon monoxide reading should not exceed 100
ppm.
TABLE 19
Firing Rate
CO2% For Nat
CO2% For L.P.
High Fire
6.0 - 7.4
6.9 - 8.4
Low Fire
4.8 - 6.0
5.7 - 7.0
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 20 for manifold
pressures, TABLE 21 for pressure switch kits and TABLE
