Air Balance; Pressure Drop Across A Dry Indoor Coil - York SUNLINE 2000 Installation Manual

AIR BALANCE

Start the supply air blower motor. Adjust the resis-
tances in both the supply and the return air duct sys-
tems to balance the air distribution throughout the
conditioned space. The job specifications may require
that this balancing be done by someone other than the
equipment installer.
To check the supply air CFM after the initial balancing
has been completed:
1. Remove the two 5/16" dot plugs from the blower
motor and the filter access panels shown in the
Unit Dimensions Figure 10 and Detail "X" Accy.
Side Supply & Return Air Openings Figure 11.
2. Insert at least 8" of 1/4 inch tubing into each of
these holes for sufficient penetration into the air
flow on both sides of the indoor coil.
The tubes must be inserted and held in a posi-
NOTE:
tion perpendicular to the air flow so that veloc-
ity pressure will not affect the static pressure
readings.
3. Using an inclined manometer, determine the pres-
sure drop across a dry evaporator coil. Since the
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
5
FIGURE 15 - PRESSURE DROP ACROSS A DRY INDOOR COIL VS SUPPLY AIR CFM
Johnson Controls Unitary Products
SUPPLY AIR
6 7
NOMINAL CFM (THOUSANDS) SUPPLY AIR
moisture on an evaporator coil may vary greatly,
measuring the pressure drop across a wet coil
under field conditions would be inaccurate. To
assure a dry coil, the compressors should be deac-
tivated 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 Pressure Drop vs. Supply Air
CFM Figure 15.
Failure to properly adjust the total system air
quantity can result in extensive blower dam-
age.
After readings have been obtained, remove the tubes
and reinstall the two 5/16" dot plugs that were removed
in Step 1.
De-energize the compressors before taking
NOTE:
any test measurements to assure a dry indoor
coil.
240 MBH
8
175245-YIM-C-1008
9 10
25