Danfoss MCHE Service guide

Service guide

User manual

Installation, Operation and

MicroChannel Heat Exchangers
MCHE

Maintenance Manual

Installation and Maintenance Guide

APP pumps (APP 21-43)

www.danfoss.com

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Sevice guide | Application, Installation and Maintenance Manual MCHE

Table of Contents Table of Contents ..................................................................................2

1. Introduction ............................................................................4

1.1 General.................................................................................4

1.2 Symbols ................................................................................4

2. Storage and working environments .....................................................5

2.1 Storage ................................................................................5

2.2 Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3 Bending procedure .....................................................................5

3. Installation..............................................................................6

3.1 Pass arrangement ......................................................................6

3.2 Fan location and size ....................................................................6

3.3 Coil mounting against thermal expansion ...............................................7

3.4 Elimination of gaps......................................................................8

3.5 Prevention of galvanic corrosion.........................................................8

3.6 Vibration ...............................................................................9

4. Leak repair ..............................................................................9

5. Coating ................................................................................10

6 Maintenance...........................................................................10

6.1 Fi lters ..................................................................................10

6.2 Shut down periods .....................................................................10

6.3 Cleaning procedure ....................................................................10

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Service guide | Application, Installation and Maintenance Manual MCHE

1. Introduction

1.1 General

This guide is for installation and maintenance of
Danfoss Microchannel Heat Exchangers (MCHEs).
We recommend that you read this manual
carefully before commencing any work.
Danfoss is not responsible or liable for any
damage caused by failure to comply with the
instructions in this manual and/or due to
incorrect installation, operation and mainte­nance of MCHEs.

All personnel being responsible for operation
and maintenance of theeat exchanger unit
must read and fully understand these instruc­tions before:

• Transportation of the MCHE unit

• Lifting the unit

• Installing the MCHE unit

• Servicing the MCHE unit

• Maintaining the MVHe unit

•

1.2 General

Indicates something to be noted by the

reader

Indicates a situation which will or could

result in personal injury and/or damage
to the MCHE

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Sevice guide | Application, Installation and Maintenance Manual MCHE

Do not lift MCHX in
inlet/outlet pipes

2. Storage and working
environments

2.1 Storage

• Microchannel heat exchangers should be
stored indoors in a dry and clean environ­ment.

• The storage temperature range is -40 °C to
121°C (-40°F to 250°F).

• Metal chips, and/or copper or steel dust can
cause galvanic corrosion, so storage and
installation areas must remain clean and
separate from machining or welding areas.
Use separate tools and/or keep tools clean.

• To minimize potential damage, we recom­mend that you keep MCHEs in their original
packaging until they are installed in the air
conditioning or refrigeration equipment.

• Improper storage and stacking of MCHEs
can cause premature corrosion or deforma­tion and will reduce MCHE’s life. Extra care
should be taken when storing MCHEs!

• Refrigerants used in MCHE shall comply with
AHRI Standard 700.

• The maximum operating pressure shall not
exceed the value shown on the Label of
MCHE.

• Never lift a MCHE by the inlet and outlet
tubes as it might result in dimensional
deviation or worse yet, the initiation of a
crack that can later result in a leak.

• Do not hit or drop MCHE on edges.

The MCHE is constructed of soft aluminum
therefore, dropping, striking, placing heavy
objects on top of, or stepping on any part of the
heat exchanger will likely cause a deformation. If
the coil becomes slightly deformed or bowed, it
is possible to flatten them back out by laying
them concave side down on a flat hard surface
and applying pressure via a large heavy flat plate
(say 3-4 square feet of ½” non-metallic sheet,
such as plywood or plastic, with a couple of
handles attached). This procedure works for
bowed coils with flush fins, but not for local fin
protrusions.

2.3 Bending procedure

The same bending machines can be used for
MCHE and tube & fin heat exchangers. In order to
optimize costs associated with shipping and
packaging, we recommend that MCHEs be
shipped flat and formed at the customer’s
location.

2.2 Handling

Compared to tube & fin coils, microchannel heat
exchangers are relatively light, the fins are harder
to bend and they are less likely to cut fingers. The
combination of these features makes MCHEs
easier to handle than tube & fin coils. However,

Bending Radius:
The minimum bend radius required to achieve
acceptable manufacturing yields is a function of
the microchannel tube, fin, and alloy, the overall
capabilities of the bending equipment including,

fixturing, bending speed and bending length.
the overall coil assembly is made of soft alu­minum, so it is susceptible to deformation (Fig.1)

NOTE: Conducting trial bending runs of the

specific coil and configuration are recommended

to verify. In general, tighter radius, thicker tubes

and longer bend lines are harder to bend. Use a

larger radius if possible.

Recommended minimum bending radii (as

determined by factory tests under favorable

conditions) are shown in Table 1 for different

microchannel tubes and fins. Consult with

Danfoss for the tubes not listed. Do not

arbitrarily extrapolate or interpolate the values.

Fig. 1 Handling attentions

Structural parameters

MC

Tub e

C116 16*1.3*16

C120 20.6*1.3*20 140 5.5

C125 25.4*1.3*26 200 7.87

Tub e

(Wmm*Hmm*Port#)

Fin

(Hmm*Gage mm)

8.1* 0.0 8

Material

3102
Tub e

+

3003MOD

Fin

Min. recommended bending R

mm in

90 3.5

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Tab le 1

Service guide | Application, Installation and Maintenance Manual MCHE

MCHE Fan Installation Face

Disstance

Inlet

Ma

Consider the following during bending:

• MCHEs are constructed of soft aluminum
and are susceptible to deformation during
handling. Prior to bending operation, make
sure the MCHE is flat, square and undam­aged. Consider a sizing operation to ensure
this.

• Make sure the coils are loaded into the
bender in a way that keeps them flat square
and undamaged.

• Keep the flat tubes perpendicular to the
spindle while bending the coil.

• Clamp the coil during the bending process,
being careful not to crush it.

• Slower bending speeds will often yield
better results.

• Vertical spindle bending machines are often
set up so that the microchannel coil ends up
sliding along the table with all its weight
supported by the header ends and/or the
bottom dead tube.

3. Installation 3.1 Pass arrangement

During the bending operation, do not let
one end of the coil become cantilevered off
the edge the table, because this can cause
the coil to droop with the tubes being
non-perpendicular to the spindle, resulting
in corkscrewing or reduced bend quality
and/or consistency. Note that with some
benders, a portion of the supporting table
will drop down during bending, creating
opportunities for cantilever loads and
improper bending.

• Bending multi-bend coils on a horizontal
spindle bender can cause cantilevered
loads resulting from the dead weight of the
unsupported bent legs. As an example, a
coil with three (3) bends, depending on
fixturing, may result in the load of the first
75% of the coil being transferred into the
remaining coil leg, possibly causing poor
bend quality and/or permanent deforma
tion. Bending challenges are greater with
MCHE’s than similar fin and tube coils,
requiring proper fixturing.

recommended to be at least 15 times the width/
depth of MCHE coil when possible (Fig.3).

Carefully identify the locations of the inlet and
outlet tubes. Microchannel condensers is often
designed with multiple passages (parallel flow)
that have fewer tubes in each successive pass
(Fig. 2)

ny tubes

4

3

2

Fig. 2 MCHE passes distribution

Danfoss MCHEs include a small notch in both
headers to indicate that this is the bottom of the
heat exchanger. Additionally, a product label is
placed on the outermost tube (unless specified
elsewhere by the customer), indicating the top of
the heat exchanger.
Incorrectly connecting the inlet and outlet tubes
of a MCHE will likely result in excessive refrige­rant side pressure drop and poor heat transfer.

3.2 Fan location and size

Air distribution may have an influence on the
performance of the MCHE. For good air distribu­tion choosing a fan with proper fan diameter and
keeping a constant distance between the coil
and the fan is desirable. We recommend
selecting a fan diameter that is as close as
possible to the smallest of MCHE height and
length. The distance between MCHE and fan is)

Outlet

Few tubes

H

L

Fig. 3 Fan location and size

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Sevice guide | Application, Installation and Maintenance Manual MCHE

Steel frame

Allow some
movemen
due to thermal
Expansion

3.3 Coil mounting against thermal expan-
sion

Thermal expansion of aluminum is higher than
most other metals. Frequent thermally induced
stress could shorten the life of the micro channel
heat exchanger (Fig.4)

50 K

Allow it to move

Allow it to move

Do not fix it in all 4 corners before you have
considered the impact from thermal expansion

To avoid the risk of thermal expansion, a micro
channel heat exchanger must be mounted with
brackets that allow some flexibility of movement.
Mounting methods as indicated in Figures 5a
and 5b are recommended.

Fig. 5a Mounting by bracket Fig. 5b Mounting by end plate

Inlet/outlet connections are not designed to be
used as handles, support mating tubes, resist
thermal expansion, or be forced into position
with mating tubes during assembly, etc. In
particular:

• Inlet/outlet connections must be assembled
& supported so that the brazed joints are
not exposed to stress/tension. (Fig.6)
Mating tubes should be pre-bent to avoid
damaging or collapsing the MCHE’s copper/
aluminum inlet/outlet tubes and/or
aluminum transition cups. Mating tubes
should be configured so that no bending or
forcing is required during installation.

Fig. 4 Coil mounting for MCHE

Sealing

MCHE

Sealing

t

Fig.6 Inlet/Outlet connection attentions

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Service guide | Application, Installation and Maintenance Manual MCHE

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 recom­mended 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.

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)

Fig. 8 Typical installation

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Sevice guide | Application, Installation and Maintenance Manual MCHE

3.6 Vibration

Vibration that exceeds a specific range may
cause the failure of MCHE. To avoid failure due to
vibration:

• Make sure vibration level meet require­ments as in table 2.

It is recommended to test on points that in the
area within 10mm to the end of the connection
tube (Fig 9)

Best practices in the case to prevent the MCHE
from the influence of vibration is using rubber
washers on the brackets or rubber supports on
the manifolds (fig.10a&10b)

Name Parameter

Amplitude/mm ≤ 0 . 1 5  (peak to peak is 0.3 mm)

Acceleration/m.s

-2

≤20

Table 2 The allowable vibration ranges

10 mm

Inlet

Outlet

10 mm

Fig. 9 Recommend test points of vibration

Fig. 10a Rubber washer Fig. 10b Rubber support

4. Leak repair is not practical to repair a MCHE refrigerant leak
in the field. Danfoss recommends replacement
of the MCHE in the event that a leak develops It
due to a defect, mechanical damage or prema­ture corrosion.

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Service guide | Application, Installation and Maintenance Manual MCHE

5. Coating Coating of a heat exchanger could increase

6. Maintenance Frequent servicing is essential to maintaining

corrosion resistance in certain applications and/
or environmental conditions such as coastal or
industrial areas, as well as situations with
stagnant water or extreme wet conditions.
Danfoss approved coating systems provide a
controlled process for the cleaning, rinsing, and
the application of the coating material with full
and even coverage. Untested coating systems
may not adhere properly to the aluminum
surface due to the flux residue left on the
aluminum surface after brazing. In addition, any
small area not covered by the coating could
potentially pose a risk of failure due to corrosion.
Thermal performance may also be reduced by
improper application of the coating resulting in
clogging or bridging between the fin and louvers

the required MCHE performance. For every
installed Danfoss MCHE, service records must be
documented.

CAUTION

Prior to servicing the MCHE, be sure to discon­nect the power supply and use lock-out
methods to prevent the power from acciden­tally being turned on.

6.1 Filters

Danfoss recommends the use of air filters on the
frontal face of the MCHE to lower the deposition
of rain water and other contaminants that can
collect on the surface of the tubes.

6.2 Shut down periods

During periods when the MCHE is not operated
for longer than a week, the MCHE must be
completely cleaned following the cleaning
procedure. This practice must also be performed
during short shut-down periods where corrosive
deposits accumulate on the MCHE.

6.3 Cleaning procedure

Relative to tube & fin heat exchangers, Micro­Channel heat exchanger coils tend to accumu­late more dirt on the surface of the coil and less
dirt inside the coil, making them easier to clean.
Follow the steps below for proper cleaning:

WARNINGS

Field applied coatings are not recommended for
brazed aluminum MicroChannel heat exchang­ers.Danfoss MicroChannel heat exchangers must
NOT be coated using any other coating, but the
ones specifically approved by Danfoss, such as
certain qualified e-coating (epoxy based
electrophoretic coating) suppliers or similar
high-quality coating technologies. Coating of a
coil using a supplier or coating process not
approved by Danfoss voids the product warranty.
It may also reduce the lifetime and/or the
performance of the MicroChannel heat
exchanger. Consult your Danfoss Sales &
Application representative for more information.

Step 1: Remove surface debris

Remove surface dirt, leaves, fibers, etc. with a
vacuum cleaner (preferably with a brush or other
soft attachment rather than a metal tube),
compressed air blown from the inside out, and/or
a soft bristle (not wire!) brush. Do not impact or
scrape the coil with the vacuum tube, air nozzle,
etc.

Step 2: Rinse

Rinse only with water. Do not use any chemicals
(including those advertised as coil cleaners) to
clean MicroChannel heat exchangers, as they
may cause corrosion.
Hose the MCHE off gently, preferably from the
inside-out and top to bottom, running the water
through every fin passage until it comes out
clean. The fins of MicroChannel coils are stronger
than traditional tube & fin coil fins but still need
to be handled with care. Do not hit the coil with
the hose. We recommend placing your thumb
over the end of the hose rather than using the
end of the nozzle to obtain a gentler spray and
reduce the possibility of impact damage.
We do not recommend using a pressure washer
to clean the coil due to the possibility of damage.
Warranty claims related to cleaning damage,
especially from pressure washers, or corrosion
resulting from chemical coil cleaners, will NOT be
honored.

Step 3: Blow dry

Depending on the installation and fin geometry,
MicroChannel heat exchangers could possibly
retain more water compared to traditional tube &
fin coils. It is advised to blow off or vacuum out
the residual water from the coil to speed up
drying and prevent pooling.
Danfoss recommends a quarterly cleaning of the
coils, as the minimum. The cleaning frequency
should be increased depending on the level of
dirt/dust accumulation and the environment
(e.g., coastal areas with chlorides and salts) or
industrial areas with aggressive substances.

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Danfoss MicroChannel Heat Exchangers (Jia Xing) Co., Ltd.
No. 8, Sangdelan Road, Wuyuan Street,
Haiyan, Zhejiang Province
314300 P.R. China
www.danfoss.com

© Danfoss | DCS (im) | 2019.01

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