20 Concealed Duct Air Conditioner
Connecting Pipes to the Indoor Unit
Pipe bending
Annealed copper pipe with small diameter (ø6.35 or ø9.52) can be easily bent manually. In this
case, secure large R(radius) for the bend section and gradually bend pipe. If annealed copper pipe
is large in diameter (ø15.88 or ø19.05), bend pipe with bender. Use bender appropriate for the pipe
diameter.
Brazing
In refrigerant piping, bending (in particular, acute bending) must be minimized to reduce piping
resistance. Bending is, however, necessary in some places by virtue of the installation position of
devices auxiliary to the packaged air conditioner, or of the building structure, piping distance or
finishing appearance. If a more acute bend is required than that attainable by pipe bender, perform
brazing using ready-made elbow. Aside from this function, brazing also serves to connect straight
pipes, generally using ready-made sockets. While brazing, protect piping against heat with wet cloth
to avoid damaging valve packing or burning thermal insulator with burner heat. While brazing, blow
inert gas (nitrogen gas or carbonic gas) to prevent formation of oxidation film in copper piping;
otherwise, the refrigerant circuit will clog. The blowing of nitrogen gas (or carbonic gas) through 3-
way valves is described in the following:
Refrigerant piping(Flare piping)
When connecting piping, be sure to keep piping dry(keep piping away from water), clean (keep
piping away from dust) and airtight (avoid refrigerant leakage).
When connecting piping on rainy days or making a through-hole in wall, take due care to prevent
water or plaster from entering piping.
CAUTION:
• This procedure is designed to prevent formation of oxidation film by
filling piping with inert gas. Note that excessive gas pressure will
generate pinholes at brazed points.
(Nitrogen gas: Supply pressure 0.05 ~ 0.1 kg/cm
2
G)
• When supplying inert gas, be sure to open one end of piping.
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