To check the supply air CFM after the initial balanc- ing has been completed:
1.Drill two (2)
2.Insert at least 8 inches of 1/4 inch tubing into each of these holes for sufficient penetration into the airflow on both sides of the evaporator coil.
3.Using an inclined manometer, determine the pressure drop across a dry evaporator coil. Since the moisture on an evaporator coil may vary greatly, measuring the pres- sure drop across the wet coil under field conditions would be inaccurate. To assure a dry coil, the refrigerant system should be
4.Knowing the pressure drop across a dry coil, the actual CFM through the unit can be determined from the curves shown in Figures
If the CFM is above or below the specified value, the supply air motor pulley may have to be readjusted. After one hour of operation, check the belt and pulleys for tightness and align- ment.
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 seal up the drilled holes in the side panel. 5/16 inch dot plugs (P/N
25"
7" | 5/16" |
| HOLE |
EVAPORATOR
COIL
22"
5/16"
HOLE
14"
FILTERS
COIL SECTION
FIGURE 25 - HOLE LOCATION FOR PRESSURE DROP READING
Unitary Products Group | 25 |