Pipe Diameter Calculation Procedure - Carrier 38XTZ 007-024 Installation, Operation And Maintenance Instructions

- Outdoor unit above the indoor unit.
Suction line
(gas)
40ABZ
indoor unit
NOTE:
* Install when the liquid column height exceeds 10 m.
- Indoor unit above the outdoor unit.
40ABZ
indoor unit
Liquid line
Refrigerant
flow
- Both units on the same level.
Suction line
(gas)
40ABZ
indoor unit
Depending on the unit installation
- Outdoor unit above the indoor unit (Fig. 45). The suction
line is unfavourable in cooling mode, the suction of the
refrigerant gas corresponds to refrigerant flow direction, and
is ascending.
The liquid line refrigerant flow direction is descending in
cooling mode and is calculated as explained later.
- Outdoor unit below the indoor unit (Fig. 46). The suction
line flow is descending in cooling mode, so that the oil flow
is not so problematic.
The liquid line flow direction is ascending in cooling
mode, and is calculated as explained later.
32
38XTZ
outdoor unit
Liquid line
Refrigerant
flow
Liquid pressure
control device*
Fig. 45
Suction line
(gas)
38XTZ
outdoor unit
Fig. 46
38XTZ
outdoor unit
Liquid line
Refrigerant
flow
Fig. 47
- The outdoor and indoor units are on the same level (Fig.
47). First make an actual outline diagram of the lines and
an exact calculation of the total equivalent length. If the
diagram shows any level changes to overcome (beams and
other structural elements) the resulting section (ascending
and descending) must be included in the calculations. This
means that for a gas pipe the diameter of the horizontal
sections, the vertical ascending and descending sections
must be calculated separately.
This means that in this type of installation, as in any other,
a section called horizontal can include sections that are not
all horizontal (see Fig. 48).
Gas pipe
Frame or roof
Beam
- Horizontal sections = A
- Vertical descending sections = B
- Vertical ascending sections = C
The calculation of the suction line, for example, includes
sections "A", as well as sections "B" and sections "C" so
that the total of the pressure loss is the total of the three
sections.

Pipe diameter calculation procedure

Once the refrigerant piping outline has been exactly defined we
can proceed with the size selection.
Suction line
To size the pipes:
- Make a diagram with the actual outline of the pipes in the
system. Record the dimensions (in metres) of the various
sections and the elements to be included (siphons, elbows,
valves, etc.).
- Calculate the equivalent length of:
Vertical sections: length in metres of the straight section
pipe run plus the equivalent length of the accessories
installed (elbows, siphons, etc.).
Horizontal sections: length in metres of the actual pipe run
plus the equivalent length of the accessories installed
(elbows, etc.).
- The total length is the sum of the equivalent lengths of the
vertical and horizontal sections.
- For the vertical sections distinguish between ascending
vertical refrigerant flow sections and descending flow
sections.
Beam
Fig. 48