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How To Install Branch Pipe; Airtight Test, Evacuation, And Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric CITY MULTI PQHY-P-YEM-A Series Installation Manual

Air-conditioners for building application, heat source unit.
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8.3. How to install branch pipe

For detail, please observe the instruction manual attached to the optional refriger-
ant branch kit.
I Joint
[Fig. 8.3.1] (P.4)
A To heat source unit
B To branch piping or indoor unit
There is no limitation on the joint mounting configuration.
If the diameter of the refrigerant piping selected by the procedures described
on page 3 is different from the size of the joint, match the sizes using a de-
formed joint. The deformed joint is included with the kit.
I Header
[Fig. 8.3.2] (P.4)
A To heat source unit
B To indoor unit
No restriction is applied to the mounting posture of the header.
If the diameter of the refrigerant piping selected using the procedures described
on page 3 and the size of the joint is different, match the sizes using a de-
formed joint. The deformed joint is included with the kit.
1. Nitrogen gas pressurization
(1) After pressurizing to the design pressure (2.94 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 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
(2.94 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 R407C compatible electric leak detector.
(3) This test may be used together the with bubble type gas leak test.
2 Evacuation
Evacuate with the ball valve of the heat source unit closed and evacuate both
the connection piping and the indoor unit from the service port provided on the
ball valve of the heat source unit using a vacuum pump. (Always evacuate from
the service port of both the liquid pipe and the gas pipe.) After the vacuum
reaches 650 Pa [abs], continue evacuation for at least one hour or more.
* Never perform air purging using refrigerant.
[Fig. 8.4.2] (P.4)
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. (For R407C models)
(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.
3 Refrigerant Charging (For R407C models)
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 below. If the cylinder has a
syphon pipe like that shown in the figure at the right, the liquid refrigerant 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 refrigerant re-
maining in the cylinder.
[Fig. 8.4.3] (P.4)
Airtight test procedure
C Hi Knob
F Gas pipe
I Valve
L Scale
When the number of pipes to be connected is smaller than the number of
header branches, install a cap to the unconnected branches. The cap is in-
cluded with the kit.
8.4. Airtight test, evacuation, and refrigerant
charging
1 Airtight test
Perform with the ball valve of the heat source unit closed, and pressurize the
connection piping and the indoor unit from the service port provided on the ball
valve of the heat source unit. (Always pressurize from both the liquid pipe and
the gas pipe service ports.)
[Fig. 8.4.1] (P.4)
A Nitrogen gas
B To indoor unit
D Lo Knob
E Hi Knob
G Liquid pipe
H Gas pipe
J Service port
<For R407C models>
The method of conducting the airtight test is basically the same as for R22 models.
However, since the restrictions have a large affect on deterioration of the refrigera-
tor oil, always observe them. Also, with nonazeotropic refrigerant (R407C, etc.),
gas leakage causes the composition to change and affects performance. There-
fore, perform the airtightness test cautiously.
• 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. (For R407C models)
• Use a pressure gauge, charge box, and other parts especially for
R407C. (For R407C models)
• An electric leak detector for R22 cannot detect leaks of R407C.
• Do not use a haloid torch. (Leaks cannot be detected.)

8.5. 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. 8.5.1] (P.5)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B
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
Heat source
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. 8.5.2] (P.5)
A Liquid pipe
B Gas pipe
D Finishing tape
E Insulater
[Fig. 8.5.3] (P.5)
C System analyzer
F Ball valve
I Heat source unit
Restriction
B Piping
D Heat insulation material A
C Electric wire
11

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