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Use a

tting if a speci

ed refrigerant pipe has a different diameter from that

of a branching pipe.

Always observe the restrictions on the refrigerant piping (such as rated

length, height difference, and piping diameter) to prevent equipment failure
or a decline in heating/cooling performance.

Either a lack or an excess of refrigerant causes the unit to make an

emergency stop. Charge the system with an appropriate amount of
refrigerant. When servicing, always check the notes concerning pipe
length and amount of additional refrigerant at both locations, the refrigerant
volume calculation table on the back of the service panel and the additional
refrigerant section on the labels for the combined number of indoor units
(Refer to item 9.2. for detailed information on refrigerant piping system).

Be sure to charge the system using liquid refrigerant.

Never use refrigerant to perform an air purge.

Always evacuate using a

vacuum pump.

Always insulate the piping properly. Insuf

cient insulation will result in a

decline in heating/cooling performance, water drops from condensation and
other such problems (Refer to item 10.4 for thermal insulation of refrigerant
piping).

When connecting the refrigerant piping, make sure the valve of the outdoor

unit is completely closed (the factory setting) and do not operate it until
the refrigerant piping for the outdoor, indoor units and BC controller has
been connected, a refrigerant leakage test has been performed and the
evacuation process has been completed.

Braze only with non-oxide brazing material for piping. Failure to do so
may damage the compressor. Be sure to perform the non-oxidation
brazing with a nitrogen purge.

Do not use any commercially available anti-oxidizing agent since it may
cause pipe corrosion and degrading of the refrigerant oil.

Please contact Mitsubishi Electric for more details.

(Refer to item 10.2. for details of the piping connection and valve operation)

Never perform outdoor unit piping connection work when it is raining.

Warning:

When installing and moving the unit, do not charge the system with any
other refrigerant other than the refrigerant speci

ed on the unit.

- Mixing of a different refrigerant, air, etc. may cause the refrigerant cycle to

malfunction and may result in severe damage.

Caution:

Use a vacuum pump with a reverse

ow check valve.

- If the vacuum pump does not have a reverse

ow check valve, the vacuum

pump oil may

ow back into the refrigerant cycle and cause deterioration of

the refrigerant oil.

Do not use the tools shown below used with conventional refrigerant.
(Gauge manifold, charge hose, gas leak detector, check valve,
refrigerant charge base, vacuum gauge, refrigerant recovery
equipment)

- Mixing of conventional refrigerant and refrigerant oil may cause the

refrigerant oil to deteriorate.

- Mixing of water will cause the refrigerant oil to deteriorate.
- R410A refrigerant does not contain any chlorine. Therefore, gas leak

detectors for conventional refrigerants will not react to it.

Manage the tools used for R410A more carefully than normal.

- If dust, dirt, or water gets in the refrigerant cycle, the refrigerant oil will

deteriorate.

Never use existing refrigerant piping.

- The large amount of chlorine in conventional refrigerant and refrigerant oil

in the existing piping will cause the new refrigerant to deteriorate.

Store the piping to be used during installation indoors and keep both
ends of the piping sealed until just before brazing.

- If dust, dirt, or water gets into the refrigerant cycle, the oil will deteriorate

and the compressor may fail.

Do not use a charging cylinder.

- Using a charging cylinder may cause the refrigerant to deteriorate.

Do not use special detergents for washing piping.

•

9.2. Refrigerant piping system

Connection example

[Fig. 9.2.1]

(P.4)

Outdoor model

High-pressure side

Low-pressure side

Total capacity of indoor units

Liquid pipe

Gas pipe

High-pressure gas pipe

Low-pressure gas pipe

Liquid pipe
Model number

Outdoor twinning kit

Outdoor unit

BC controller (standard)

BC controller (main)

BC controller (sub)

Indoor unit (15 ~ 80)

Indoor unit (100 ~ 250)

Outdoor twinning kit

*1 The pipe sizes listed in columns A1 to A2 in this table correspond to the sizes

for the models listed in the unit 1 and 2 columns. When the order of unit 1 and
2 is changed, make sure to use the appropriate pipe size for the model.

Precautions for outdoor unit combinations
Refer to [Fig. 9.2.2] for the positioning of twinning pipes.

[Fig. 9.2.2]

(P.6)

<A> The piping from the outdoor units to twinning pipe must be made to slope

downwards the twinning pipe. (high-pressure side only)

<B> Slope of twinning pipes (high-pressure side only)

Make sure the slope of the twinning pipes are at an angle within ±15° to the
ground.
If the slope exceeds the speci

ed angle, the unit may be damaged.

<C> Pipe connection example

The distributor on the low-pressure side must be placed in the outdoor
unit that has a larger capacity index of the two, regardless of the relative
positions of the outdoor units or their addresses.
(If outdoor units that have the same capacity are used in combination, the
distributor can be placed in either outdoor unit.)
If the distributor is placed in the outdoor unit that has a smaller capacity,
refrigerant will not be properly distributed and compressor failure may result.

Downward slope

Upward slope

BC controller

Twinning pipe

Slope of the twinning pipe is at an angle within ±15° to the ground

Twinning pipe (low-pressure side)

Twinning pipe (high-pressure side)

On-site piping (low-pressure connecting pipe: between outdoor units)

On-site piping (low-pressure main pipe: to BC controller)

On-site piping (high-pressure main pipe: to BC controller)

Straight run of pipe that is 500 mm or more

Caution: