Step 5 — complete refrigerant piping connections – Carrier 38AU User Manual

Page 10

faces, plywood sheets may be placed against the sides of the

unit, behind cables. Run cables to a central suspension point so

that the angle from the horizontal is not less than 45 degrees.

Raise and set the unit down carefully.
If it is necessary to roll the unit into position, mount the unit on

longitudinal rails, using a minimum of 3 rollers. Apply force to

the rails, not the unit. If the unit is to be skidded into position,

place it on a large pad and drag it by the pad. Do not apply any

force to the unit.
Raise from above to lift the unit from the rails or pad when unit

is in its final position.
After the unit is in position, remove all shipping materials and

top crating.

Step 5 — Complete Refrigerant Piping

Connections

PROVIDE SAFETY RELIEF — The 38AU unit is provided

with a fusible joint in the suction line in accordance with

applicable UL standards for pressure relief. If local codes

dictate an additional safety relief device, purchase locally and

install locally. Installation will require the recovery of the

factory shipping charge before the factory tubing can be cut

and the supplemental relief device is installed.
Model 38AUD has two separate refrigeration systems. If

required, each circuit will require a field-supplied/installed

supplemental relief device.

Table 4 — Equivalent Lengths for Common Fittings (ft)

CHECK 38AU MODEL WITH EVAPORATOR COIL CON-

NECTIONS — Confirm before installation of unit that the

evaporator coil connections are consistent with this 38AU

model. See Table 3 on page 9.
DETERMINE REFRIGERANT LINE SIZES — Select the

recommended line sizes for 38AUZ and 38AUD unit from the

appropriate tables.
Determine the linear length of interconnecting piping required

between the outdoor unit and indoor unit (evaporator).

Consider and identify also the arrangement of the tubing path

(quantity and type of elbows in both lines), liquid line solenoid

size, filter drier and any other refrigeration specialties located

in the liquid line. Refer to the indoor unit installation

instructions for additional details on refrigeration specialties

devices.
Determine equivalent line length adjustments for path and

components and add to linear line lengths. See Table 4,

Equivalent Lengths for Common Fittings, for usual fitting

types. Also identify adjustments for refrigeration specialties.

Refer to Part 3 of the Carrier System Design Manual for

additional data and information on equivalent lengths.
NOTE: Equivalent line lengths will vary based on tube

diameter. Calculate equivalent line length for each pipe by

adding equivalent length adjustments to linear lengths for

each pipe.
Enter the appropriate table to select the recommended line

sizes.

Liquid Lift – A liquid lift condition exists when the outdoor

unit is located below the indoor (evaporator) unit and liquid

flows vertically up in a portion of the liquid line. The vertical

column of liquid reduces the available state point subcooling at

the evaporator coil’s thermal expansion valve. This effect

reduces the length of liquid lift (feet of elevation) that a liquid

line size can accommodate. Longer linear tube lengths will also

reduce the amount of liquid lift possible.
Check Tables 5 (38AUZ) and 6 (38AUD) for maximum liquid

lift capabilities for line sizes. Reselect the liquid line tube size if

necessary. If maximum available tube size cannot provide the

required lift distance on this installation, relocate the outdoor

unit to reduce the equivalent line length or the lift requirement.
Suction Riser – A suction riser condition exists when the

outdoor unit is located above the indoor (evaporator) unit and

suction vapor must flow vertically up to return to the

compressor. Oil return is a concern when the suction tube size

is too large to produce the minimum refrigerant velocity to

ensure oil return at minimum load conditions.
Check Table 7 for maximum suction tube size for 38AU units

at minimum load conditions. Consider suction speed riser

(reduced tube size for vertical segment only) or double suction

riser arrangement if the recommended suction tube size does

not provide necessary minimum flowrates for this riser.

IMPORTANT: Do not bury refrigerant piping underground.

IMPORTANT: A refrigerant receiver is not provided with

the unit. Do not install a receiver.

Nominal

Tube OD

Elbows

90° Std

90° Lrad 90° Street

45° Std

45° Street

1.3

0.8

2.2

0.6

1.4

0.9

2.3

0.7

1.1

1.6

2.5

0.8

1.3

1.8

1.2

2.9

0.9

1.5

1.4

3.2

0.9

1.6

2.6

1.7

4.1

1.3

2.1

3.3

2.3

5.6

1.7

2.6

6.3

2.1

3.4

3.3

8.2

2.6

4.5

Nominal

Tube OD

Tees

Branch

Flow

Straight-Thru

No Reduct

Reduce 25% Reduce 50%

2.6

0.8

1.1

1.3

2.7

0.9

1.2

1.4

1.6

3.5

1.2

1.7

1.8

1.4

1.9

1.7

2.3

2.6

2.3

3.1

3.3

2.6

3.7

3.3

4.7

Model:

Line Sizes Table Quantity of Line Sets

38AUZ

38AUD