Mitsubishi Heavy Industries SRC25QA-S Technical Manual Download

Page: 65 / 102

-62-

(3) Lubricants for R410A

Mineral oil, AB (Alkybenzene), etc. are widely used as the lubricants for R22. R410A is not
easily dissolved in conventional lubricants such as mineral oil, etc. and such lubricants likely
stay in refrigerant cycle, so ester, ether and other synoil in which R410A is highly dissoluble
are generally used. However, such synoil has high hygroscopicity, so they must be handled
more carefully than conventional lubricants. In addition, if such synoil is mixed with mineral
oil, AB (Alkybenzene), etc., this may cause deterioration, thus blocks the hush pipe or causes
failure of compressor. Therefore, never mix these synoil.

7.1.2 Safety of installation/ servicing

The pressure of R410A is higher than that of R22 by about 1.6 times, so unreasonable
installation/ servicing may cause severe consequences. Therefore, be sure to use tools and
materials designed specifically for R410A, conduct installation/ servicing carefully, and pay
attention to the following precautions.
1) Never use refrigerants other than R410A in air conditioners designed to use R410A.
2) In case of refrigerant gas leakage during installation/ servicing, be sure to provide sufficient

ventilation.

If the refrigerant gas is exposed to fire, poisonous gas may be produced.
3) Prevent air or vapor from entering the refrigerant cycle when installing or removing air

conditioners. Otherwise, the pressure in the refrigerant cycle may become exceptionally high,
which will cause fracture of equipment or personal injury.

4) After the installation is completed, check that there is no refrigerant gas leakage.
If the refrigerant gas is leaked to the room and comes into contact with the fire in the fan

driven heater, small heating stove, etc., it may produce poisonous gas.

5) If an air conditioner charged with large amount of refrigerant (such as a multi-functional air

conditioner

) is installed in a small room, be sure to take more care and ensure that the

concentration will not exceed the limit even in case of refrigerant leakage.

In case the refrigerant is leaked and its concentration exceeds the limit, oxygen starvation may

be caused.

6) Be sure to conduct installation or removal according to the Installation Manual.
Incorrect installation may cause failure of refrigerant, water leakage, electric shocks, fire, etc.
7) Unauthorized operation of air conditioners may be very dangerous. In case of failure of the

machine

, please call the qualified air conditioner technician or electrician.

Incorrect servicing may cause water leakage, electric shocks, fire, etc.

7.2 Mounting refrigerant pipes
7.2.1 Piping materials and joints used

Refrigerant pipes are mounted mainly with copper pipes and joints. Be sure to select and mount
copper pipes and joints suitable for refrigerant. In addition, be sure to use clean copper pipes and
joints and try to keep their inner walls clean.

(1) Copper pipes
Be sure to use seamless copper pipes made of copper or copper alloy. Copper pipes with

residual oil less than 40mg/10m are ideal. Do not use fractured, distorted or discolored copper
pipes (especially in respect of inner walls). Otherwise, the filth may block the EEV or hush
pipe.
As the pressure of air conditioners using R410A is higher than that of air conditioners using
R22, be sure to select appropriate materials.
The thickness of copper pipes for R410A is shown in Table 3. Never use copper pipes with a
thickness less than 0.8mm.

Table 3 Thickness of annealed copper pipes

Thickness (mm)

Rating diameter

Outside diameter

(mm)

R410A

[Reference]

R22

1/4

6.35

0.80

3/8