Service guide | Application, Installation and Maintenance Manual MCHE
7
AX292455807588en-000101 | 01.2019 |
Plastic heat shrink tubing prevents galvanic
corrosion in the MCHE’s copper to aluminum
joint by keeping moisture from entering the area .
A minimum of 70mm length from the Cu/Al joint
to the connection point is required to protect the
Cu-Al brazing joint and plastic shrink tube from
excessive heat during the brazing process . When
brazing copper piping to the MCHE, it is recom-
mended to use dry nitrogen purging along with
a heat sink and/or wrapping the copper stub
tube with a wet cloth to protect the Cu/Al joint
and heat shrink tubing from excessive heat . This
also applies to microchannel heat exchangers
with aluminum inlet/outlet tubes . Depending on
the location of the connections relative to the
heat exchanger, a heat shield may be required to
protect the MCHE’s tubes and fins from the
brazing torch . The recommended pipe length
“L” after the brazing joint should be greater than
or equal to 70mm as shown in the picture below
(Fig .7) .
L≥70 mm
Fig . 7 Recommended length of inlet/outlet
connections
3.4 Elimination of gaps
To maximize heat transfer performance, gaps
should be eliminated on both sides of the face of
the MCHE . Gaps should also be eliminated on
the top, bottom and sides of the MCHE so that all
fan induced air is directed over the coil surface .
This can be accomplished with sealing strips as
shown in Fig . 8 .
Fig . 8 Typical installation
3.5 Prevention of galvanic corrosion
Aluminum is a chemically reactive metal and will
corrode when combined with most metals that
are used today in industrial manufacturing . To
avoid any galvanic corrosion, it is necessary to
separate Al and other metals . The best way to
prevent galvanic corrosion is to use plastic/
rubber/foam as a means to isolate the aluminum
coil from dissimilar metals (Fig 8)
