Table of Contents
Advertisement
START-UP
System Evacuation and Dehydration —
GTAC II (General Training Air Conditioning), Module 4, "De-
hydration for Proper Evacuation and Dehydration Techniques."
Preliminary Charge —
Charging, Recovery, Recycling, and Reclamation for charging
procedures. Using the liquid charging method and charging by
weight procedure, charge each circuit with the amount of re-
frigerant (R-410A or R-134a depending on unit configuration)
listed in Table 16.
Adjust Refrigerant Charge
CAUTION
Never charge liquid into the low pressure side of system.
Do not overcharge. During charging or removal of refriger-
ation, be sure indoor fan system is operating. Failure
to comply could result in personal injury or equipment
damage.
CAUTION
Charging procedures for MCHX (microchannel heat
exchanger) units require very accurate measurement tech-
niques. Charge should be added in small increments. Using
cooling charging charts provided, add or remove refriger-
ant until conditions of the chart are met. As conditions get
close to the point on the chart, add or remove charge in
1
/
lb (100 gram) increments until complete. Ensure that all
4
fans are on and all compressors are running when using
charging charts. Failure to comply may result in equipment
damage.
Table 16 — Preliminary Refrigerant Charge, lb (kg)
R-410A
UNIT SIZE
Circuit A
Circuit B
09DPS018
9.6
09DPS020
12.0
09DPS030
12.0
09DPM035
12.0
09DPM040
12.0
09DPM050
12.0
09DPM060
12.0
09DPM065
17.6
09DPM075
26.4
09DPM085
31.7
09DPM095
26.4
09DPM115
35.2
09DPM130
44.0
NOTES:
1. Preliminary charge does not take into account interconnecting piping
between indoor and outdoor units.
2. For liquid line piping longer than 25 ft (7.6 m) with R-410A refrigerant, use
the following information:
1
/
in. (12.7 mm) liquid line — 0.6 lb per 10 linear ft (0.27 kg per 3 m)
2
5
/
in. (15.9 mm) liquid line — 1.0 lb per 10 linear ft (0.45 kg per 3 m)
8
7
/
in. (22.2 mm) liquid line — 2.0 lb per 10 linear ft (0.91 kg per 3 m)
8
1
1
/
in. (28.6 mm) liquid line — 3.5 lb per 10 linear ft (1.59 kg per 3 m)
8
3. For liquid line piping longer than 25 ft (7.6 m) with R-134a refrigerant, use
the following information:
1
/
in. (12.7 mm) liquid line — 0.7 lb per 10 linear ft (0.32 kg per 3 m)
2
5
/
in. (15.9 mm) liquid line — 1.2 lb per 10 linear ft (0.53 kg per 3 m)
8
7
/
in. (22.2 mm) liquid line — 2.4 lb per 10 linear ft (1.06 kg per 3 m)
8
1
1
/
in. (28.6 mm) liquid line — 4.1 lb per 10 linear ft (1.80 kg per 3 m)
8
Refer to
Refer to GTAC II, Module 5,
R-134a
Circuit A
Circuit B
—
11.1
—
—
13.9
—
—
13.9
—
12.0
13.9
13.9
12.0
13.9
13.9
12.0
13.9
13.9
12.0
13.9
13.9
17.6
20.3
20.3
17.6
30.5
20.3
21.1
36.6
24.4
26.4
30.5
30.5
26.4
40.6
30.5
26.4
50.8
30.5
Due to the compact design of microchannel heat exchang-
ers, refrigerant charge is reduced significantly. As a result,
charging procedures for MCHX units require very accurate
measurement techniques. Charge should be added in small
increments. Add or remove refrigerant until conditions are
met. As conditions get close to the desired point, add or
remove charge in
1
/
lb (100 gram) increments until complete.
4
Ensure that all fans are on and all compressors are running
when charging. If charging at low outdoor ambient, the con-
denser coil can be partially blocked in order to increase head
pressure.
With all fans operating and all compressors on the circuit
being serviced operating at full capacity, adjust the refrigerant
charge to obtain desired subcooling. Charge vapor into com-
pressor low-side service port. Measure pressure at the liquid
line port, making sure a Schrader depressor is used. Also, mea-
sure liquid line temperature as close to the liquid service port as
possible.
If the sight glass is cloudy, check refrigerant charge again.
Ensure all fans and compressors on the circuit being serviced
are operating. Also ensure maximum allowable liquid lift has
not been exceeded. If the sight glass is cloudy, a restriction
could exist in the liquid line. Check for a plugged filter drier or
partially open solenoid valve. Replace or repair, as needed.
Head Pressure Control —
reduces condensing capacity under low ambient temperature
conditions.
FAN CYCLING — The 09DP units are shipped from the fac-
tory equipped to work down to ambient temperatures listed in
Tables 14 and 15. This is accomplished by cycling condenser
fans based on ambient temperature switch (ATS) and fan cy-
cling pressure switches. The ATS opens at approximately 60 F
and closes at approximately 65 F. The ATS is located below the
control box behind the front access panel on the 020-060 and at
the bottom of the control box on the 065-130 unit sizes.
The 040-060 and 075-130 size units need fan cycling pres-
sure switches (FCPS) installed. The units are shipped from the
factory with switches for use with R-410A. The switches are
set to open at 289 psig (1993 kPa) and close at 445 psig
(3068 kPa). The 30HXA units which are designed for use with
R-134a are shipped from the factory with FCPS to be used with
the 09DP units. The R-134a switch open point is 97 psig
(669 kPa) and close point is 185 psig (1275 kPa).
Fan contactor and fan motor operation is shown in
Tables 17 and 18.
LIQUID LINE PRESSURE SET POINT ADJUST-
MENT — Adjusting the set point may be necessary to avoid
interaction with other head pressure control devices. If adjust-
ment is necessary, use the set point parameter found in P34 for
R-410A or P35 for R-134a. A lower value will result in a lower
liquid line set point. As an example for R-410A, decreasing the
P34 from 24 to 23 will decrease the liquid line pressure by ap-
proximately 15 psig (103 kPa). As an example for R-134a, de-
creasing the P35 from 12.6 to 11.6 will decrease the liquid line
pressure by approximately 15 psig (103 kPa). It is recommend-
ed to adjust P34 for R-410A units by 1 and P35 for R-134a
units by 0.5 increments.
37
The head pressure control
Advertisement
Table of Contents
