4.5 Line Set Installation
• If tubing is to be run underground, it must be run in
a sealed watertight chase.
• Use care in routing tubing and do not kink or twist.
Use a good quality tubing bender on the vapor line
to prevent kinking.
• Route the tubing using temporary hangers; then
straighten the tubing and install permanent hangers.
The tubing must be adequately supported.
• Isolate the vapor line from the building structure. If
the vapor line comes in contact with inside walls,
ceiling, or flooring, the vibration of the vapor line
4.5.1 Important Tubing Installation Practices
Observe the following when installing correctly
sized type "L" refrigerant tubing between the
outdoor unit and indoor coil:
• Check Table 2 for the correct vapor line size and
liquid line size.
• If a portion of the liquid line passes through a
very hot area where liquid refrigerant can be
heated to form vapor, insulating the liquid line
• Use clean, dehydrated, sealed refrigeration-grade
• Always keep tubing sealed until tubing is in place
and connections are to be made.
• A high-quality biflow filter drier is included with all
R-410A heat pump units and must be installed in
the liquid line upon unit installation.
• When replacing an R-22 system with an R-410A
system and the line set is not replaced, blow out
the lines with dry nitrogen to remove as much
of the remaining mineral oil as possible. Check
for low spots where oil may be trapped and take
measures to drain the oil from those areas.
in the heating mode will result in noise inside the
• Blow out the liquid and vapor lines with dry nitrogen
before connecting to the outdoor unit and indoor
coil to remove debris that can plug the expansion
• If tubing has been cut, debur the ends while
holding the tubing in a position to prevent chips
from falling into tubing. Burrs such as those
caused by tubing cutters can affect performance
dramatically, particularly on small diameter liquid
• For best operation, keep tubing run as short as
possible with a minimum number of elbows or
• Locations where the tubing will be exposed to
mechanical damage should be avoided. If it is
necessary to use such locations, the copper
tubing should be protected by a housing to