Carrier 38AUZ appendix INSTALL LIQUID LINE SOLENOID VALVE Optional

in the liquid line. Refer to the indoor unit installation instructions for additional details.

Determine equivalent line length adjustments for path and components and add to linear line lengths. See Tables 2 and 3; also refer to Part 3 of the Carrier System Design Manual and E20-II® software for design details and line sizing.

Suction line sizing – Select a tube size that produces a suction pressure drop in range of 1.5 to 3.0°F (0.8 to 1.7°C). (Higher pressure drops are permissible but there will be a loss in cooling capacity due to the higher pressure drop.) Insulate the suction line.

Liquid line sizing – For linear line lengths up to 50-ft (15 m), select a tube size that produces a liquid pressure drop of approximately 2°F (1.1°C). For linear line lengths greater than 50-ft (15 m), select a line size that will permit the liquid state-point subcooling entering the indoor coil’s TXV to be a minimum of 2°F (1.1°C).

Hot Gas Bypass – Hot gas bypass, if used, should be introduced before the evaporator. (A bypass route that also bypasses the evaporator circuit may lead to oil trapping in the evaporator circuit during low load conditions and then to oil slugging as evaporator load increases.) Model 38AUZA units do not include a hot gas stub connection; a tee must be field- supplied and installed in the compressor discharge line. Run a ½-in OD line between outdoor unit and evaporator coil inlet. Install an Auxiliary Side Connector at the evaporator between TXV and distributor (follow instructions for the side connector part). Insulate the hot gas line.

Note that refrigerant suction piping should be insulated.

IMPORTANT: For 38AUZ*07-14 applications with liquid lift greater than 20 ft (6 m), use 5/8-in. liquid line. Maximum lift is 60 ft (18 m).

Table 2 — Liquid Line Data —

38AUZ*07-14 60 Hz Units,

MAXIMUM	LIQUID LINE
	Maximum	Maximum
ALLOWABLE	Allowable	Allowable
LIQUID LIFT	Pressure	Temp.
ft (m)	Drop	Loss
	psig (kPa)	°F (°C)
60 (18)	7 (48)	2 (1)

*Inlet and outlet.

NOTE: Data shown is for units operating at 45°F (7.2°C) saturated suction temperature and 95°F (35°C) entering air temperature. For 38AUZ*07-14 applications with liquid lift greater than 20 ft (6 m), use 5/8-in. liquid line. Maximum lift is 60 ft (18 m).

Table 3 — Refrigerant Piping Sizes —

38AUZ*07-14 60 Hz Units

LINEAR LENGTH OF INTERCONNECTING PIPING —

FT (m)

UNIT

0-25

25-50

50-75

75-100

38AU

(0-7.5)

(7.5-15)

(15-23)

(23-30)*

Line Size

(in. OD)

L

S

L

S

L

S

L

S

Z*07

3/8

11/8

3/8

11/8

3/8

11/8

3/8

11/8

Z*08

3/8

11/8

1/2

11/8

1/2

11/8

1/2

13/8

Z*12

1/2

13/8

1/2

13/8

1/2

13/8

1/2

13/8

Z*14

1/2

13/8

1/2

13/8

1/2

13/8

1/2

13/8

LEGEND

L — Liquid Line

S — Suction Line

*Field-supplied suction accumulator required for pipe length 75-100 ft (23-30 m).

NOTES:

1.Pipe sizes are based on a 2°F (1°C) saturated temperature loss for liquid and suction lines.

2.Pipe sizes are based on the maximum linear length, shown for each column, plus a 50% allowance for fittings.

3.Charge unit with R-410A and verify that subcooled liquid exists at TXV by checking for a full liquid line sight glass or by calcu- lating subcooling at TXV.

INSTALL FILTER DRIER(S) AND MOISTURE INDICATOR(S) — Every unit should have a filter drier and a liquid-moisture indicator (sight glass). Refer to Table 4. In some applications, depending on space and convenience re- quirements, it may be desirable to install 2 filter driers and sight glasses. One filter drier and sight glass may be installed at A locations in Fig. 5; or, 2 filter driers and sight glasses may be installed at B locations.

Select the filter drier for maximum unit capacity and minimum pressure drop. Complete the refrigerant piping from the indoor unit to the outdoor unit before opening the liquid and suction lines at the outdoor unit.

INSTALL LIQUID LINE SOLENOID VALVE — SOLENOID DROP — It is recommended that a solenoid valve be placed in the main liquid line (see Fig. 5) between the condensing unit and the evaporator coil. Refer to Table 4. (A liquid line solenoid valve is required when the liquid line length exceeds 75 ft [23 m] or when the condensing unit is con- nected to a chiller barrel in a built-up chiller system.) This valve prevents refrigerant migration (which causes oil dilution) to the compressor during the off cycle, at low outdoor ambient temperatures. Wire the solenoid in parallel with the compressor contactor coil (see Fig. 5). This means of electrical control is referred to as solenoid drop control.

INSTALL LIQUID LINE SOLENOID VALVE (Optional)

—CAPACITY CONTROL — If 2-step cooling is desired, place a solenoid valve in the location shown in Fig. 5.

MAKE PIPING CONNECTIONS — Piping connections at the 38AU unit are ball valves with stub tube extensions. Do not open the unit service valves until all interconnecting tube braz- ing as been completed.

The stub tube connections include ¼-in SAE service fittings with Schrader valve cores (see Fig. 6). Before making any brazed connections to the unit service valves, remove both Schrader valve caps and cores and save for re-installation. Con- nect a source for nitrogen to one of these service fittings during tube brazing to prevent the formation of copper oxides inside the tubes at brazed joints.

When connecting the field tubing to the 38AU service valves, wrap the valves in wet rags to prevent overheating.

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