York PHG6A24 Installation Manual page 26

5322625-UIM-A-0417
External Static Pressure Setup
To measure external static pressure:
• Measure the supply air static pressure. See Figure 13.
• Record this positive number.
• Measure the return air static pressure.
• Record this negative number.
• Treat the negative number as a positive, and add the two numbers
together.
• This is total system static.
Checking Gas Heat 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 revo-
lution of the hand on the smallest 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 Table 21.
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.
NOTICE
To find the BTU input, multiply the number of cubic feet of gas con-
sumed per hour by the BTU content of the gas in your particular
locality. (Contact your gas company for this information since it varies
widely from city to city.)
FIGURE 13: Measuring External Static Pressure
26
Table 21: Gas Rate Cubic Feet Per Hour
Seconds for9
One Rev.
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
1. EXAMPLE: By actual measurement, it takes 38 seconds for the hand on
the 1-cubic foot dial to make a revolution with just a 100,000 BTUH furnace
running. Using this information, locate 38 seconds in the first column of
Table 15. 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 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.
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
34 67
32 64
31 62
30 60
Johnson Controls Unitary Products