6
REFRIGERANT LINE DESIGN AND SIZING — Consider
the length of the piping required between the outdoor and
indoor units. The maximum allowable line length is 100 ft
(30.5 M). Select proper liquid and vapor line sizes from
Table 4. Refer to the Carrier System Design Manual, Part 3, for
design details and proper piping practices.
Table 4 — Piping Selection and Refrigerant
Charge Data
LEGEND
*Approximately 4 elbows assumed in determining pipe sizes.
†
Maximum length of interconnecting piping is 100 ft (30.5 m).
**Approximate system charge is for estimating only. It includes
charge requirements for one outdoor unit, matching indoor coil,
and interconnecting piping. See Preliminary Charge section on
page 15.
NOTE: If there is a vertical separation between indoor and outdoor
units, see Table 3. Double vapor line riser may be required.
Carefully evaluate any vapor risers at minimum load condi-
tions to ensure proper compressor oil return. If the indoor unit
is above the outdoor unit, the riser will function as a hot gas ris-
er. If the outdoor unit is above the indoor unit, the riser is a suc-
tion riser. Design and construct a double riser if necessary. Re-
fer to the Carrier System Design Manual, Part 3, or Carrier’s
computer-based E20-II
®
Refrigerant Piping Design program.
LIQUID LINE PIPING PROCEDURE — Pipe the system liq-
uid line as follows:
1. Open service valves in sequence:
a. Discharge service valve on compressor.
b. Suction service valve on compressor.
c. Liquid line valve.
2. Remove
1
/
4
-in. flare cap from liquid valve Schrader port.
3. Attach refrigerant recovery device and recover holding
charge.
4. Remove runaround loop.
5. Connect system liquid line from liquid connection of out-
door (38AQS) unit to indoor unit liquid line connections.
See Fig. 5A and 5B for typical piping and wiring. Select
proper field-supplied bi-flow filter driers and install in the
liquid line. See Fig. 6. Install a field-supplied liquid mois-
ture indicator between the filter drier(s) and the liquid
connections on the indoor (40RMQ) unit. Braze or silver
alloy solder all connections. Pass nitrogen or other inert
gas through piping while making connections to prevent
formation of copper oxide. (Copper oxides are extremely
active under high temperature and pressure. Failure to
prevent collection of copper oxides may result in system
component failures.)
VAPOR LINE PIPING PROCEDURE — Connect system
vapor line to the vapor line stub on the outdoor unit and the
vapor stubs on the indoor unit. At the indoor unit, construct
vapor piping branches as shown in Fig. 7 for good mixing
of the refrigerant leaving the indoor coil during cooling. This
will ensure proper TXV (thermostatic expansion valve) bulb
sensing.
Where vapor line is exposed to outdoor air, line must be in-
sulated. See Table 5 for insulation requirements.
Table 5 — Insulation for Vapor Line Exposed to Outdoor Conditions
*Recommended vapor line insulation for piping exposed to outdoor conditions to prevent loss of heating during heating
cycle. When vapor line goes through interior spaces, insulation should be selected to prevent condensation on cooling
cycle. Heating capacity should be reduced 1000 Btuh (295 W) if over 35 ft (11 m) of vapor line with
3
/
4
in. (19 mm) insu-
lation is exposed to outdoor conditions.
†Closed cell foam insulation with a thermal conductivity of:
0.28 Btu • in./ft
2
• h • °F (0.04 W/m • °C).
OUTDOOR
UNIT
38AQS
LENGTH OF PIPING — FT (M)*
MAXIMUM
LIQUID
LINE OD
(in.)
0-25
(0-7.6)
25-60
(7.6-18.3)
60-100†
(18.3-30.5)
Line Size (in. OD)
L
V
L
V
L
V
012
5
/
8
1
1
/
8
5
/
8
1
3
/
8
5
/
8
1
5
/
8
5
/
8
016
5
/
8
1
3
/
8
3
/
4
1
5
/
8
3
/
4
1
5
/
8
3
/
4
Approximate System Charge lb (kg)**
Maximum
Charge —
lb (kg)
012
30 (14)
38 (17)
46 (21)
48 (21.8)
016
37 (17)
45 (20)
59 (27)
62 (28.1)
L —
Liquid Line
V —
Vapor Line
Unit is pressurized with a holding charge of refrigerant.
Recover R-22 holding charge before removing runaround
liquid piping loop. Failure to recover holding charge before
removing piping loop could result in equipment damage
and severe injury.
LENGTH OF EXPOSED
VAPOR LINE*
INSULATION THICKNESS†
ft
m
in.
mm
10
3
3
/
8
10
25
8
1
/
2
13
35
11
3
/
4
19
50
15
3
/
4
19