Adjustment Of Temperature Rise - York DM036 Installation Manual

consumed per hour from the Gas Rate - Cubic Feet Per
Hour (Table 27).
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.)
Table 27: Gas Rate - Cubic Feet Per Hour
Seconds for one
rev.
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
Johnson Controls Unitary Products
1
Size of Test Dial
1/2 cu. ft. 1 cu. ft.
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
Table 27: Gas Rate - Cubic Feet Per Hour
Seconds for one
rev.
54
56
58
60
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 col-
umn headed "1 Cubic Foot", where you will see that 95 cubic
feet of gas per hour are consumed by the furnace 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.

Adjustment Of Temperature Rise

The temperature rise (or temperature difference between the
return air and the heated air from the furnace) must lie within
the range shown on the rating plate and the data in the Gas
Heat Application Table 3.
Btuh Input x 0.8
=
CFM
108 .
After the temperature rise has been determined, the Volumetric
Flow Rate can be calculated as follows:
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts (about six feet from the furnace) where
they will not be affected by radiant heat. Increase the blower
Volumetric Flow Rate to decrease the temperature rise;
decrease the blower Volumetric Flow Rate to increase the rise.
Refer to the Blower Motor and Drive Data Table 21.
5011492-XIM-B-0815
1
Size of Test Dial
1/2 cu. ft. 1 cu. ft.
34 67
32 64
31 62
30 60
.
43