Johnson Controls DW-03 - Burner Air Shutter Adjustment; Checking Gas Input; Natural Gas; Adjustment of Temperature Rise

362247-BIM-B-0109
52 Johnson Controls Unitary Products
Burners are now accessible for service.
Reverse the above procedure to replace the assem-
blies. Make sure that burners are level and seat at the
rear of the heat exchanger.
BURNER AIR SHUTTER ADJUSTMENT
Adjust burner shutters so no yellow flame is observed
in the heat exchanger tubes.
CHECKING GAS INPUT
NATURAL GAS
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 small-
est dial on the meter. A typical gas meter usually
has a 1/2 or a 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 from the Gas
Rate - Cubic Feet Per Hour (Table 36).
If the actual input is not within 5% of the furnace rating
(with allowance being made for the permissible range
of the regulator setting), replace the orifice spuds with
spuds of the proper size.
NOTE: To find the Btu input, multiply the number of
cubic feet of gas consumed per hour by the
Btu content of the gas in your particular locality
(contact your gas company for this information
- it varies widely from city to city.)
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise (or temperature difference
between the return air and the heated air from the fur-
nace) must lie within the range shown on the rating
plate and the data in the Gas Heat Application Table 4.
FIGURE 22 - TYPICAL FLAME APPEARANCE
TABLE 36:GAS RATE - CUBIC FEET PER HOUR
1
1. By actual measurement, it takes 38 seconds for the hand on
the 1-cubic foot dial to make a revolution with a 100,000
Btuh furnace running. Using this information, located 38
seconds in the first column in the table above. Read across
to the column headed “1 Cubic Foot”, where you will see
that 95 cubic feet of gas per hour are consumed by the fur-
nace at that rate. Multiply 95 X 1050 (the Btu rating of the
gas obtained from the local gas company). The result is
99,750 Btuh, which is close to the 100,000 Btuh rating of the
furnace.
Seconds for one
rev.
Size of Test Dial
1/2 cu. ft. 1 cu. ft.
10 180 360
12 150 300
14 129 257
16 113 225
18 100 200
20 90 180
22 82 164
24 75 150
26 69 138
28 64 129
30 60 120
32 56 113
34 53 106
36 50 100
38 47 95
40 45 90
42 43 86
44 41 82
46 39 78
48 37 75
50 36 72
52 35 69
54 34 67
56 32 64
58 31 62
60 30 60