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7. 7.
Resistance measurement of transmission cable
(Measure with breaker OFF)
Do not turn on the power if the resistance between the terminals of the transmission
cable is abnormal. Otherwise, the PC board may be damaged.
Measure the resistance between 2 terminals of a transmission cable.
(1) Transmission cable connecting indoor units, outdoor units, and signal amplifi ers
Measure the resistance of the signal amplifi er terminal and the terminal of the indoor and
outdoor units connected farthest away from the device where terminal resistor is mea-
sured.
A value from the table is displayed, depending on the distance from the signal amplifi er and
the device where the terminal resistor is set.
This value is an estimate.
(2) Transmission cable connecting outdoor units in a refrigerant system
The resistance between the terminals of the transmission cable is 45 to 60 Ω.
This value is an estimate.
Distance from terminal resistor [ft (m)]
0 ~328
(0 ~100)
A short circuit somewhere or 2 or more terminal resistors are con-
0 ~ 50
nected
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190 ~
Faulty contact or wiring length over 1,640 ft (500 mm)
1K ~∞
Faulty contact, open circuit, or no termination resistor
8. PIPE INSTALLATION II
Fig. A Connection system
Outdoor unit
Indoor
Indoor
unit
unit
Fig. B
Service hose with valve core
Charging port
Blank cap
Hexagon wrench
3/16 in (4mm)
Table. A
Pipe
3-way valve
Liquid
5.2 to 6.6 lbf·ft
valve
(7.0 to 9.0 N·m)
Gas
8.1 to 9.6 lbf·ft
valve
(11.0 to 13.0 N·m)
En-17
CAUTION
~656
~984
~1,312
(~200)
(~300)
(~400)
Pressure regulating valve
Pressure gauge
Nitrogen
Vacuum
Scale
pump
Charging port cap
3-way valve
Connecting pipe
Blank cap
Charging port cap
14.8 to 18.5 lbf·ft
9.2 to 11.8 lbf·ft
(20.0 to 25.0 N·m)
(12.5 to 16.0 N·m)
22.1 to 25.8 lbf·ft
9.2 to 11.8 lbf·ft
(30.0 to 35.0 N·m)
(12.5 to 16.0 N·m)
8. 1.
Sealing test - Pressure (leak) testing
Use only nitrogen gas.
Never use refrigerant gas, oxygen, fl ammable gas or poisonous gas to pressurize the
system. (If oxygen is used. There is danger of an explosion.)
Do not shock during sealing test.
It can rupture the pipes and cause serious injury.
Do not turn on the power unless all operations are complete.
Do not block the walls and the ceiling until the sealing test and charging of the refrigerant
gas have been completed.
After connecting the pipes, perform a sealing test.
Recheck that the spindle of the 3-way valve are closed before performing a sealing test.
(Fig. B)
Pour nitrogen gas through both the liquid pipe and the gas pipe.
Pressurize nitrogen gas to 609 psi (4.2 MPa) to perform the sealing test.
Check all fl are connection and brazed areas.
Then, check that the pressure has not decreased.
Compare the pressures after pressurizing and letting it stand for 24 hours, and check that
~1,640
the pressure did not decreased.
(~500)
* When the outdoor temperature changes 9 degrees F (5 degrees C), the test pressure
changes 7.25 psi (0.05 MPa.).
If the pressure has dropped, the pipe joints may be leaking.
If a leakage is found, immediately repair it and perform a sealing test again.
* Decrease the pressure of nitrogen gas before brazing
After completing the sealing test, release the nitrogen gas from both valves.
Release the nitrogen gas slowly.
8. 2.
Vacuum process
Do not turn on the power unless all operations are complete.
If the system is not evacuated suffi ciently, its performance will drop.
Be sure to evacuate the refrigerant system using a vacuum pump.
The refrigerant pressure may sometimes not rise when a closed valve is opened after
the system is evacuated using a vacuum pump. This is caused by the closure of the re-
frigerant system of the outdoor unit by the electronic expansion valve. This will not affect
the operation of the unit.
Use a clean gauge manifold and charging hose that were designed specifi cally for use
with R410A. Using the same vacuum equipment for different refrigerants may damage
the vacuum pump or the unit.
Do not purge the air with refrigerants, but use a vacuum pump to evacuate the system.
• If moisture enter the piping, follow below. (i.e., if doing work during the rainy season,
if the actual work takes long enough that condensation may form on the inside of the
pipes, if rain might enter the pipes during work, etc.)
• After operating the vacuum pump for 2 hours, pressurize to 7.25 psi (0.05 MPa)
(i.e., vacuum breakdown) with nitrogen gas, then depressurize down to 500 microns
(-100.7 kPa) for an hour using the vacuum pump (vacuum process).
• If the pressure does not reach 500 microns (-100.7 kPa) even after depressurizing for
at least 2 hours, repeat the vacuum breakdown - vacuum process perform triple evacu-
ation procedure as necessary to bring the vacuum down to 500 microns (-100.7 kPa)
or lower.
After vacuum process, maintain the vacuum for an hour and make sure the pressure
does not rise by monitoring with a vacuum gauge.
Evacuation procedure
(1) Remove the caps of the gas pipe and liquid pipe and check that the valves are closed.
(2) Remove the charging cap.
(3) Connect a vacuum pump and a pressure gauge to a charging hose and connect it to
the charging port.
(4) Activate the vacuum pump and vacuum the indoor unit and connection piping until the
pressure gauge becomes 500 microns (-100.7 kPa).
Evacuate from both the gas pipe and the liquid pipe.
(5) Continue evacuating the system for 1 hour after the pressure gauge reads
500 microns (-100.7 kPa).
(6) Remove the charging hose and reinstall the charging cap.
CAUTION
CAUTION
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