Thermal Insulation Of Refrigerant Piping; Wiring; Caution - Mitsubishi Electric PUH-8 Installation Manual

Outdoor unit
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1. Nitrogen gas pressurization
(1) After pressurizing to the design pressure (3.3 MPa) using nitrogen gas, let 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 brazed parts, 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 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 the liquid pipe and the gas pipe.) After the vacuum reaches
5 Torr, continue evacuation for at least one hour or more.
* Never perform air purging using refrigerant.
[Fig. 8.2.2] (P.5)
A System analyzer
B Lo Knob
D Ball valve
E Liquid pipe
G Service port
H Three-way joint
J Valve
K Cylinder
M Vacuum pump
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 0.5 Torr or greater after operating
for five minutes.

8.3. 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. 8.3.1] (P.5)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B

9. Wiring

9.1. Caution

1 Follow ordinance of your governmental organization for technical standard re-
lated to electrical equipment, wiring regulations and guidance of each electric
power company.
2 Set up the outdoor unit so that the wiring for the remote controller and the M-
NET (MELANS) wiring do not produce electrical interference with the power
supply cable. (Do not route them together in the same conduit.)
3 Be sure to provide designated grounding work to outdoor unit.
12
Airtight test procedure
C Hi Knob
F Gas pipe
I Valve
L Scale
B Piping
D Heat insulation material A
• If a flammable gas or air (oxygen) is used as the pressurization
gas, it may catch fire or explode.
• Never use refrigerant gas for purpose of airtight test.
Heat
Glass fiber + Steel wire
insulation
Adhesive + Heat - resistant polyethylene foam + Adhesive tape
material A
Indoor
Vinyl tape
Outer
Floor exposed
Water-proof hemp cloth + Bronze asphalt
covering B
Water-proof hemp cloth + Zinc plate + Oily
Outdoor
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. 8.3.2] (P.5)
A Liquid pipe
B Gas pipe
D Finishing tape
E Insulator
[Fig. 8.3.3] (P.5)
Penetrations
[Fig. 8.3.4] (P.5)
<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.)
4 Give some allowance to wiring for electrical part box of indoor and outdoor
units, because the box is sometimes removed at the time of service work.
5 In the indoor/outdoor connection wiring, the power and signals wiring are con-
tained in the same multiconductor cable. Since the cable is polarized, be sure
the connection is according to the terminal number.
6 For detailed information about the power supply cable, see the manual sup-
plied with the indoor unit.
Restriction
C
Electric wire
<B> Outer wall
<D> Floor (fireproofing)
B Heat insulating material
D Caulking material
F Waterproofing layer
H Lagging material

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