A
PPLICATION
GUIDELINES
S
YSTEM
DESIGN
RECOMMENDATIONS
Essential piping design
considerations
Proper piping practices should be employed to
ensure adequate oil return, even under minimum
load conditions with special consideration given
to the size and slope of the tubing coming from
the evaporator. Tubing returns from the evapora-
tor should be designed so as not to trap oil and to
prevent oil and refrigerant migration back to the
compressor during off-cycles.
If the evaporator lies above the compressor the
addition of a pump-down cycle is strongly recom-
mended. If a pump-down cycle were to be omit-
ted, the suction line must have a loop at the evap-
orator outlet to prevent refrigerant from draining
into the compressor during off-cycles.
If the evaporator were situated below the com-
pressor, the suction riser must be trapped to en-
sure the oil return to the compressor (see fig.1).
When the condenser is mounted at a higher po-
sition than the compressor, a suitably sized «U»-
shaped trap close to the compressor is necessary
to prevent oil leaving the compressor from drain-
ing back to the discharge side of the compressor
during off cycle. The upper loop also helps avoid
condensed liquid refrigerant from draining back
to the compressor when stopped (see fig. 2). The
maximum elevation difference between the in-
door and outdoor section cannot exceed 26 ft.
System manufacturers should specify precautions
for any applications that exceed these limits to en-
sure compressor reliability.
Piping should be designed with adequate three-
dimensional flexibility (figure 2). It should not be
in contact with the surrounding structure, unless
a proper tubing mount has been installed. This
protection proves necessary to avoid excess vi-
bration, which can ultimately result in connection
or tube failure due to fatigue or wear from abra-
sion. Aside from tubing and connection damage,
excess vibration may be transmitted to the sur-
rounding structure and generate an unaccept-
able sound level within that structure as well (for
more information on sound and vibration, see the
section on: «Sound and vibration management»
page 31).
General
Successful application of scroll compressors is de-
pendent on careful selection of the compressor
for the application. If the compressor is not correct
for the system, it will operate beyond the limits
given in this manual. Poor performance, reduced
reliability, or both may result.
25
FRCC.PC.016.A1.22
0.5 % slope,
13 ft/s or more
0.5 % slope,
13 ft/s or more
U-trap
U-trap, as short as possible
U-trap, as short as possible
max. 13 ft
fig.1
max. 13 ft
26 to 40 ft/s
To condenser
Evaporator
Condenser
HP
U-trap
3D flexibility
Upper loop
LP
fig. 2
