Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric CITY MULTI PUHY-P850YSGM-A Manual De Instalación

1. Nitrogen gas pressurization
(1) After pressurizing to the design pressure (4.15 MPa) using nitrogen gas, allow it to stand for
about one day. If the pressure does not drop, airtightness is good.
However, if the pressure drops, since the leaking point is unknown, the following bubble test
may also be performed.
(2) After the pressurization described above, spray the flare connection parts, brazed parts, flanges,
and other parts that may leak with a bubbling agent (Kyuboflex, etc.) and visually check for
bubbles.
(3) After the airtight test, wipe off the bubbling agent.
2. Pressurization using refrigerant gas and nitrogen gas
(1) Pressurizing to a gas pressure of approximately 0.2 MPa, pressurize to the design pressure
(4.15 MPa) using nitrogen gas.
However, do not pressurize at one time. Stop during pressurization and check that the pres-
sure does not drop.
(2) Check for gas leaks by checking the flare connection parts, brazed parts, flanges, and other
parts which may leak using an R410A compatible electric leak detector.
(3) This test may be used together the with bubble type gas leak test.
Caution:
Only use refrigerant R410A.
- The use of other refrigerant such as R22 or R407C, which contains chlorine, will
deteriorate the refrigerating machine oil or cause the compressor to malfunction.
2 Evacuation
Evacuate with the ball valve of the outdoor unit closed and evacuate both the
connection piping and the indoor unit from the service port provided on the ball
valve of the outdoor unit using a vacuum pump. (Always evacuate from the
service port of both liquid pipe and gas pipe.) Evacuate the oil balance con-
necting pipe between the Main unit and the Sub unit through the service port
by the oil balance stop valve with that valve closed, using the vacuum pump.
After the vacuum reaches 650 Pa [abs], continue evacuation for at least one
hour or more.
* Never perform air purging using refrigerant.
[Fig. 10.3.2] (P.5)
A System analyzer B Lo knob
D Ball valve E Liquid pipe
G Service port H Three-way joint
J Valve K R410A cylinder
M Vacuum pump N To indoor unit
P Main unit side Q Sub unit side
S Service port for oil balance pipe
T Oil balance pipe (Between outdoor units)
U Service panel (Left side)
V To liquid distributor (Accessory)
Note:
• Always add an appropriate amount of refrigerant. Also always seal the
system with liquid refrigerant. Too much or too little refrigerant will cause
trouble.
• Use a gauge manifold, charging hose, and other parts for the refrigerant
indicated on the unit.
• Use a graviometer. (One that can measure down to 0.1 kg.)
• Use a vacuum pump with a reverse flow check valve.
(Recommended vacuum gauge: ROBINAIR 14830A Thermistor Vacuum
Gauge)
Also use a vacuum gauge that reaches 65 Pa [abs] or below after operat-
ing for five minutes.
3 Refrigerant Charging
Since the refrigerant used with the unit is nonazerotropic, it must be charged in
the liquid state. Consequently, when charging the unit with refrigerant from a
cylinder, if the cylinder does not have a syphon pipe, charge the liquid refriger-
ant by turning the cylinder upside-down as shown in Fig.10.3.3. If the cylinder
has a syphon pipe like that shown in the picture on the right, the liquid refriger-
ant can be charged with the cylinder standing upright. Therefore, give careful
attention to the cylinder specifications. If the unit should be charged with gas
refrigerant, replace all the refrigerant with new refrigerant. Do not use the re-
frigerant remaining in the cylinder.
[Fig. 10.3.3] (P.6)
A Syphon pipe B In case of the cylinder having no syphon pipe.
14
Airtight test procedure
C Hi knob
F Gas pipe
I Valve
L Scale
O Outdoor unit
R Stop valve for oil balance
• If a flammable gas or air (oxygen) is used as the pressurization
gas, it may catch fire or explode.
• Do not use a refrigerant other than that indicated on the unit.
• Sealing with gas from a cylinder will cause the composition of
the refrigerant in the cylinder to change.
• Use a pressure gauge, charging hose, and other parts especially
for R410A.
• An electric leak detector for R22 cannot detect leaks of R410A.
• Do not use a haloid torch. (Leaks cannot be detected.)

10.4. Thermal insulation of refrigerant piping

Be sure to give insulation work to refrigerant piping by covering liquid pipe and gas
pipe separately with enough thickness heat-resistant polyethylene, so that no gap
is observed in the joint between indoor unit and insulating material, and insulating
materials themselves. When insulation work is insufficient, there is a possibility of
condensation drip, etc. Pay special attention to insulation work to ceiling plenum.
[Fig. 10.4.1] (P.6)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B
Glass fiber + Steel wire
Heat
insulation
Adhesive + Heat - resistant polyethylene foam + Adhesive tape
material A
Indoor Vinyl tape
Outer
Floor exposed Water-proof hemp cloth + Bronze asphalt
covering B
Outdoor Water-proof hemp cloth + Zinc plate + Oily paint
Note:
• When using polyethylene cover as covering material, asphalt roofing shall
not be required.
• No heat insulation must be provided for electric wires.
[Fig. 10.4.2] (P.6)
A Liquid pipe B Gas pipe
D Finishing tape E Insulator
[Fig. 10.4.3] (P.6)
Penetrations
[Fig. 10.4.4] (P.6)
<A> Inner wall (concealed)
<C> Outer wall (exposed)
<E> Roof pipe shaft
<F> Penetrating portion on fire limit and boundary wall
A Sleeve
C Lagging
E Band
G Sleeve with edge
I Mortar or other incombustible caulking
J Incombustible heat insulation material
When filling a gap with mortar, cover the penetration part with steel plate so that
the insulation material will not be caved in. For this part, use incombustible materi-
als for both insulation and covering. (Vinyl covering should not be used.)
• Insulation materials for the pipes to be added on site must meet the following
specifications:
ø6.35 to 25.4 mm
Thickness
Temperature Resistance
* Installation of pipes in a high-temperature high-humidity environment, such as
the top floor of a building, may require the use of insulation materials thicker
than the ones specified in the chart above.
* When certain specifications presented by the client must be met, ensure that
they also meet the specifications on the chart above.
Restriction
B Piping
D Heat insulation material A
C Electric wire
<B> Outer wall
<D> Floor (waterproofing)
B Heat insulating material
D Caulking material
F Waterproofing laye
H Lagging material
Pipe size
ø28.58 to 41.28 mm
10 mm min. 15 mm min.
100 °C min.