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035-17477-001 Rev. A (801)
INLET
WRENCH
BOSS
ON/OFF SWITCH
Gas Valves - (Top) White-Rodgers
FIGURE 37 :
(Bottom) Honeywell (Approved for Field
Replacement)
CHECKING GAS INPUT (NATURAL GAS)
NOTE: Front door of burner box must be secured when
checking gas input.
1.
Turn off all other gas appliances connected to the gas
meter.
2.
With the furnace turned on, measure the time needed for
one revolution of the hand on the smallest dial on the
meter. A typical domestic gas meter usually has a 1/2 or
1 cubic foot test dial.
3.
Using the number of seconds for each revolution and the
size of the test dial increment, find the cubic feet of gas
consumed per hour, (Table 9 on Page 27).
NOTE: To find the Btuh input, multiply the number of cubic
feet of gas consumed per hour by the BTU content of the gas
in your particular locality. Contract your gas company for this
information, as it varies widely from city to city.
EXAMPLE: It is found by measurement that it takes 26 sec-
onds for the hand to turn on the 1 cubic foot dial to make a
revolution with only a 120,000 Btuh furnace running. Using
this information, locate 26 seconds in the first column of.
Unitary Products Group
Read across to the column headed 1 Cubic Foot where you
will see that 138 cubic feet of gas per hour are consumed by
the furnace at that rate. Multiply 138 by 850 (the BTU rating
of the gas obtained from the local gas company). The result is
117,300 Btuh, which is close to the 120,000 Btuh rating of the
OUTLET
furnace.
If the actual input is not within +2% of the furnace rating, with
allowance being made for the permissible range of the regu-
lator setting (0.3 inches W.C.), replace the orifice spuds with
spuds of the proper size.
MAIN REGULATOR
ADJUST
Table 9: GAS RATE (CUBIC FEET PER HOUR)
Be sure to relight any gas appliances that were
turned off at the start of this input check.
SECONDS FOR
1/2 CUBIC
ONE REVOLUTION
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
SIZE OF TEST DIAL
1 CUBIC FOOT
FOOT
180
360
150
300
129
257
113
225
100
200
90
180
82
164
75
150
69
138
64
129
60
120
56
113
53
106
50
100
47
95
45
90
43
86
41
82
39
78
37
75
36
72
35
69
34
67
32
64
31
62
30
60
27
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