035-13329-001-B-0504
Unitary Products Group
17
1.
Remove the (two) 5/16" dot plugs from the holes located
on the filter access panel side of the unit.
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 evaporator coil.
NOTE: The tubes must be inserted and held in a position
perpendicular to the air flow so that velocity pres -
sure will not affect the static pressure readings.
3.
Using an inclined manometer, determine the pressure
drop across a dry indoor coil. Since the moisture on an
indoor 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 de-energized 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 Figure 8.
5.
After readings have been obtained, remove the tubes
and seal the holes with the 5/16” dot plugs removed in
Step 1.
NOTE: De-energize the compressors before taking any test
measurements to assure a dry indoor coil.
SECURE OWNER’S APPROVAL
When the system is functioning properly, secure the owner’s
approval. Show him the location of all disconnect switches
and the thermostat. Teach him how to start and stop the unit
and how to adjust temperature settings within the limitations
of the system.
MAINTENANCE
NORMAL MAINTENANCE
FILTERS - Inspect once a month. Replace disposable or
clean permanent type as necessary. DO NOT replace perma-
nent type with disposable.
MOTORS - Indoor fan and outdoor fan motors are perma-
nently lubricated and require no maintenance.
OUTDOOR COIL - Dirt should not be allowed to accumulate
on the outdoor coil surface or other parts in the air circuit.
Cleaning should be as often as necessary to keep coil clean.
Use a brush, vacuum cleaner attachment, or other suitable
means. If water is used to clean coil, be sure power to the
unit is shut off prior to cleaning.
NOTE: Exercise care when cleaning the coil so that the coil
fins are not damaged.
Do not permit the outdoor air discharge to be obstructed by
overhanging structures of shrubs.
FIGURE 8 - PRESSURE DROP ACROSS A DRY
EVAPORATOR COIL VS. SUPPLY AIR CFM,
WITHOUT AIR FILTERS
Failure to properly adjust the total system air quan-
tity can result in poor system performance.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
750
1250
1750
2250
2750
3250
3750
036
048
NOMINAL CFM
PRE
SS
URE DROP
(
IWG)
060
Prior to any of the following maintenance proce-
dures, shut off all power to the unit to prevent per-
sonal injury.
