Page 19
13HPD SERIES
Optimizing System Charge
This section outlines procedures for optimizing the system
charge.
NOTE Gauge set should be connected as illustrate in
figure 14; however, refrigerant tank should be turned
right−side−up to deliver refrigerant gas during charge
optimizing procedure.
1. 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.
2. Move the low side manifold gauge hose from the vapor
line service valve to the true suction port (see figure 1
in the unit installation instruction).
Make sure the
refrigerant cylinder is right−side−up so that it will
deliver gas during the charge optimizing
procedure
.
3. Set the thermostat for a cooling demand. Turn on
power to the indoor unit and close the outdoor unit
disconnect switch to start the unit.
4. Allow unit to run for five minutes to allow pressures to
stabilize.
5. Check and adjust indoor airflow using procedures
provided below for heating mode and figure 16 for
cooling mode.
6. Use either
approach
or
subcooling
method (see
figures 17 and 18 for optimizing system charge. Adjust
charge as necessary.
7. Close gauge set valves and disconnect gauge set.
8. Replace the stem and service port caps and tighten as
specified in
Operating Service Valves
on page 3.
9. Recheck voltage while the unit is running. Power must
be within range shown on the nameplate.
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 =
Amperage x Volts x 3.41
1.08 x Temperature Rise (F)
1. Determine the desired
D
T
Measure entering air temper-
ature using dry bulb (
A
) and wet bulb (
B
).
D
T
is the intersect-
ing 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
). Tem-
perature 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 within
+3º, no adjustment is needed. See examples: Assume
D
T
=
15 and
A
temp. = 72º, these
C
temperatures would necessi-
tate 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 tempera-
tures to confirm that the temperature drop and
D
T are within
+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
AIRFLOW
Figure 16. Cooling Mode Indoor Airflow Check