Sunlife Enterprises DM180, DM300, DM240 Drop, Pressure, Nominal Cfm Thousands Supply Air

356214-XIM-A-0108

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 Dimensions and Clearances Figure 13.

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.

NOTE: The tubes must be inserted and held in a posi- 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 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 18.

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.

NOTE: DE-ENERGIZE THE COMPRESSORS BEFORE TAKING ANY TEST MEASURE- MENTS TO ASSURE A DRY INDOOR COIL.

	0.65
(IWG)	0.6	180 MBH			240 MBH			300 MBH
	0.55
DROP	0.5
	0.45
PRESSURE
	0.4
	0.35
	0.3
	0.25
	4	5	6	7	8	9	10	11	12	13

NOMINAL CFM (THOUSANDS) SUPPLY AIR

FIGURE 18 - PRESSURE DROP ACROSS A DRY INDOOR COIL VS SUPPLY AIR CFM FOR ALL UNIT TONNAGES

Johnson Controls Unitary Products 35