Page 17
XP19 SERIES
8. Check system for sufficient refrigerate by using the
procedures listed under
Testing and Charging
System
.
TESTING AND CHARGING SYSTEM
This system uses HFC−410A refrigerant which operates at
much higher pressures than HCFC−22. The pre−installed
liquid line filter drier is approved for use with HFC−410A
only. Do not replace it with components designed for use
with HCFC−22. This unit is NOT approved for use with coils
which use capillary tubes as a refrigerant metering device.
SETTING UP TO CHECK CHARGE
1. Close manifold gauge set valves. Connect the center
manifold hose to an upright cylinder of HFC−410A.
2. Connect the manifold gauge set to the unit’s service
ports as illustrated in Figure 3.
D
low pressure gauge to
vapor service port
D
high pressure gauge to
liquid service port
COOLING MODE INDOOR AIRFLOW CHECK
Check airflow using the Delta−T (
D
T)
process using the
illustration in Figure 30.
HEATING MODE INDOOR AIRFLOW CHECK
Blower airflow (CFM) may be calculated by energizing
electric heat and measuring:
S
Temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
S
Measuring voltage supplied to the unit,
S
Measuring amperage being drawn by the heat unit(s).
Then, apply the measurements taken in following formula
to determine CFM:
CFM =
Amps x Volts x 3.41
1.08 x Temperature rise (F)
CALCULATING CHARGE
If the system is void of refrigerant, first, locate and repair
any leaks and then weigh in the refrigerant charge into the
unit. To calculate the total refrigerant charge:
Amount
specified
on
nameplate
Adjust amount. for
variation in line set
length listed on Table
in Figure 31.
Additional charge
specified per
indoor unit
match−up listed in
Tables 4 through
7.
Total
charge
+
+
=
1. Determine the desired
D
T
Measure entering air temperature
using dry bulb (
A
) and wet bulb (
B
).
D
T
is the intersecting value of
A
and
B
in the Table (see triangle).
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
.
3. Determine if fan needs adjustment
If the difference between the
measured
T
Drop
and the desired
D
T
(T
Drop
–
D
T)
is 3º, no ad-
justment 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
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.
D
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 30. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
