Page 14
505361M 09/07
Step 1. Determine the desired
D
T
Measure entering air tempera-
ture using dry bulb (
A
) and wet bulb (
B
).
D
T
is the intersecting value of
A
and
B
in the table (see triangle).
Step 2. Find temperature drop across coil
Measure the coil’s dry
bulb entering and leaving air temperatures (
A
and
C
). Temperature
Drop Formula: (
T
Drop
) =
A
minus
C
.
Step 3. Determine if fan needs adjustment
If the difference be-
tween the measured
T
Drop
and the desired
D
T
(T
Drop
–
D
T)
is within
+3º, no adjustment is needed. See examples: Assume
D
T
= 15 and
A
temp. = 72º, these
C
temperatures would necessitate stated actions:
Cº T
Drop
–
D
T
=
ºF
ACTION
53º
19
–
15
=
4
Increase the airflow
58º
14
–
15
=
−1
(3º range) no change
62º
10
–
15
=
−5
Decrease the airflow
Step 4. Adjust the fan speed
See indoor unit instructions to in-
crease/decrease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and
D
T are 3º.
Delta−
T
80
24 24 24 23 23 22 22 22 20 19 18 17 16 15
78
23 23 23 22 22 21 21 20 19 18 17 16 15 14
76
22 22 22 21 21 20 19 19 18 17 16 15 14 13
74
21 21 21 20 19 19 18 17 16 16 15 14 13 12
72
20 20 19 18 17 17 16 15 15 14 13 12 11 10
70
19 19 18 18 17 17 16 15 15 14 13 12 11 10
57 58 59 60 61 62 63 64 65 66 67 68 69 70
Temp.
of air
entering
indoor
coil ºF
INDOOR
COIL
DRY
BULB
DRY
BULB
WET
BULB
B
T
Drop
19º
A
Dry−bulb
Wet−bulb ºF
A
72º
B
64º
C
53º
air flow
air flow
All temperatures are
expressed in ºF
Figure 23. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
Start−Up Procedures
IMPORTANT
If unit is equipped with a crankcase heater, it should
be energized 24 hours before unit start−up to
prevent compressor damage as a result of slugging.
1. Rotate fan to check for binding.
2. Inspect all factory− and field−installed wiring for loose
connections.
3. After evacuation is complete, open the liquid line and
vapor line service valves to release the refrigerant
charge (contained in outdoor unit) into the system.
4. Replace the stem caps and tighten as specified in
Operating Service Valves
on page 2.
5. Check voltage supply at the disconnect switch. The
voltage must be within the range listed on the unit’s
nameplate. If not, do not start the equipment until you
have consulted with the power company and the
voltage condition has been corrected.
6. Set the thermostat for a cooling demand. Turn on
power to the indoor indoor unit and close the outdoor
unit disconnect switch to start the unit.
7. Recheck voltage while the unit is running. Power must
be within range shown on the nameplate.
8. Check system for sufficient refrigerate by using the
procedures listed under
Testing and Charging
System
.
SETTING UP TO CHECK CHARGE
1. Close manifold gauge set valves. Connect the center
manifold hose to an upright cylinder of HCFC−22.
2. Connect the manifold gauge set to the unit’s service
ports as illustrated in figure 1.
low pressure gauge to
vapor service port
high pressure gauge to
liquid service port
COOLING MODE INDOOR AIRFLOW CHECK
Check airflow using the Delta−T (
D
T)
process as illustrated
in figure 23.
HEATING MODE INDOOR AIRFLOW CHECK
Blower airflow (CFM) may be calculated by energizing
electric heat and measuring:
temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
voltage supplied to the unit,
amperage being drawn by the heat elements.
Then, apply the measurements taken in following formula
to determine CFM:
CFM =
Amps x Volts x 3.41
1.08 x Temperature rise (F)
The unit is factory charged with the amount of HCFC−22
refrigerant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with a 15
foot (4.6 m) line set. For varying lengths of line set, refer to
table 6 for refrigerant charge adjustment.
Table 6. Refrigerant Charge per Line Set Lengths
Liquid Line Set
Diameter
Ounces per 5 feet (g per 1.5 m) adjust
from 15 feet (4.6 m) line set*
3/8 in. (9.5 mm)
3 ounce per 5 ft. (85 g per 1.5 m)
NOTE − *If line length is greater than 15 ft. (4.6 m), add this amount. If
line length is less than 15 ft. (4.6 m), subtract this amount.
The outdoor unit should be charged during warm weather.
However, applications arise in which charging must occur
in the colder months.
The method of charging is
determined the
outdoor ambient temperature
.
Measure the liquid line temperature and the outdoor
ambient temperature as outlined below:
1. Close manifold gauge set valves. Connect the
manifold gauge set to the service valves.
low pressure gauge to
vapor
valve service port
high pressure gauge to
liquid
valve service port
2. Connect the center manifold hose to an upright
cylinder of HCFC−22.
