Johnson Controls 340968-XIM-A-0108 Manual De Usuario
340968-XIM-A-0108
18
Johnson Controls Unitary Products
CHECKING SUPPLY AIR CFM
To check the supply air CFM after the initial balancing
has been completed:
has been completed:
1.
Remove the two ¼ inch dot plugs in the duct panel.
2.
Insert at least 8 inches of ¼ inch tubing into each of
these holes for sufficient penetration into the airflow on
both sides of the indoor coil.
these holes for sufficient penetration into the airflow on
both sides of the indoor coil.
3.
Using an inclined manometer, determine the pressure
drop across the dry evaporator coil. Since the moisture
on an evaporator coil may vary greatly, measuring the
pressure drop across a wet coil under field conditions
would be inaccurate. To ensure a dry coil, the compres-
sors should be deactivated while the test is being run.
drop across the dry evaporator coil. Since the moisture
on an evaporator coil may vary greatly, measuring the
pressure drop across a wet coil under field conditions
would be inaccurate. To ensure a dry coil, the compres-
sors should be deactivated while the test is being run.
4.
Knowing the pressure drop across a dry coil, the actual
CFM through the unit can be determined from the curve
in Coil Delta P vs. Supply Air CFM figure.
CFM through the unit can be determined from the curve
in Coil Delta P vs. Supply Air CFM figure.
After readings have been obtained, remove the tubes and
reinstall the two ¼ inch plugs removed in Step 1.
reinstall the two ¼ inch plugs removed in Step 1.
De-energize the compressors before taking any test mea-
surements to ensure a dry indoor coil.
surements to ensure a dry indoor coil.
TABLE 12: GASE RATE - CUBIC FEET PER HOUR
1
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 12. 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.
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 12. 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.
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
Failure to properly adjust the total system air quan-
tity can result in extensive system damage.
tity can result in extensive system damage.