Pipe Sizing With Refrigerant For 30Wga Units; General Considerations And Pipe Size Limits; Pipe Sizing; Discharge Pipe Sizing - Carrier AquaSnap 61WG Series Installation, Operation And Maintenance Instructions

8 - PIPE SIZING WITH REFRIGERANT FOR 30WGA UNITS

8.1 - General considerations and pipe size
limits
Pipe size limits
30WGA
Linear length (discharge - liquid line)
Height difference
The pipes must be as short as possible and have the least possible
changes (bends etc.) to minimise pressure drops. If there is a risk of
poor piping use, adequate measures must be taken (design,
positioning, protection) to prevent incorrect use.
The following constraints must be taken into account whe
the refrigerant pipes are sized:
- Oil return to the compressor is ensured by entrainment.
A minimum refrigerant velocity is required to ensure
entrainment. This velocity depends on the pipe diameter,
the refrigerant and oil temperature (these are treated as
being the same in most cases). A reduction of the pipe
diameter permits an increase of the refrigerant velocity.
The problem of a minimum entrainment velocity does
not exist for the pipes that carry liquid refrigerant as the
oil is fully miscible here.
- The pressure drop at the compressor discharge (pipes
linking the compressor outlet to the condenser inlet)
must be limited to avoid system performance losses
(increased compressor power input and decreased
cooling capacity). Increasing the pipe diameter permits
limiting the pressure drops.

8.3 - Discharge pipe sizing

The discharge piping must be sized to achieve reasonable pressure drops: a variation of 1.5 K of the saturated tempe-rature is normally
accepted (approx. 90 kPa variation for a condensing temperature of 45 °C).
Table 1 - Discharge line piping
30WGA
Equivalent length
0-10 m
10-20 m
20-30 m
30-40 m
40- 50 m
50-60 m
60-70 m
70 m or more
30WGA
Equivalent length
0-10 m
10-20 m
20-30 m
30-40 m
40- 50 m
50-60 m
60-70 m
70 m or more
(1) Recommended diameters to ensure oil return in the application range.
Maximum
30 m
12 m
(1)
020 025 030
in 3/4 3/4 7/8
in 7/8 7/8 7/8
in 7/8 1-1/8 1-1/8
in 1-1/8 1-1/8 1-1/8
in 1-1/8 1-1/8 1-1/8
in 1-1/8 1-1/8 1-1/8
in 1-1/8 1-1/8 1-1/8
in 1-1/8 1-1/8 1-1/8
110 120
in 1-3/8 1-3/8
in 1-3/8 1-3/8
in 1-3/8 1-3/8
in 1-5/8 1-5/8
in 1-5/8 1-5/8
in 1-5/8 1-5/8
in 1-5/8 1-5/8
in 1-5/8 1-5/8
- The pressure drop in the liquid line (linking the condenser
outlet to the expansion device) must not result in a
change of phase. The estimate of these pressure drops
must include those generated by possible accessories
such as solenoid valves and filter driers.
- In applications with low outside temperature and with
long pipes use of a check valve at the condenser outlet
is recommended to overcome the poor supply of the
expansion device during the start-up phase. Select a
valve that is not pressure-tight to avoid significant
pressure rises of the liquid refrigerant that may be
trapped between the solenoid valve (tight) and the check
valve.

8.2 - Pipe sizing

The following procedure can be used for pipe sizing:
- Measure the length (in metres) of the piping under
consideration.
- Add 50% to take account of special characteristics.
- Read the pipe size from tables 1 and 2 below.
- Calculate the equivalent lengths for parts included in the
piping under consideration (such as valves, filters,
connections). The equivalent lengths are normally available
from the component supplier. Add these lengths to the length
calculated above.
- Repeat steps 3 and 4 if necessary.
- See tables "Discharge line piping" and "Liquid line piping"
below.
035 040 045 050
7/8 7/8 7/8 1-1/8
1-1/8 1-1/8 1-1/8 1-1/8
1-1/8 1-1/8 1-1/8 1-3/8
1-1/8 1-1/8 1-1/8 1-3/8
1-1/8 1-3/8 1-3/8 1-3/8
1-1/8 1-3/8 1-3/8 1-3/8
1-3/8 1-3/8 1-3/8 1-3/8
1-3/8 1-3/8 1-3/8 1-3/8
140 150
1-3/8 1-1/8
1-3/8 1-1/8
1-3/8 1-3/8
1-5/8 1-3/8
1-5/8 1-3/8
1-5/8 1-3/8
1-5/8 1-5/8
1-5/8 1-5/8
060 070 080 090
1-1/8 1-1/8 1-1/8 1-1/8
1-1/8 1-3/8 1-3/8 1-3/8
1-3/8 1-3/8 1-3/8 1-3/8
1-3/8 1-3/8 1-3/8 1-5/8
1-3/8 1-3/8 1-3/8 1-5/8
1-3/8 1-3/8 1-3/8 1-5/8
1-3/8 1-3/8 1-3/8 1-5/8
1-3/8 1-3/8 1-3/8 1-5/8
170 190
1-1/8 1-1/8
1-1/8 1-1/8
1-3/8 1-3/8
1-3/8 1-3/8
1-3/8 1-3/8
1-3/8 1-3/8
1-5/8 1-5/8
1-5/8 1-5/8
45