En-26
8.7. Resistance measurement of transmission cable
(Measure with breaker OFF)
CAUTION
Do not turn on the power if the resistance
between the terminals of the transmis-
sion cable is unusual. Otherwise, the PC
board may be damaged.
Measure the resistance between 2 termi-
nals of a transmission cable.
(1) Transmission cable connecting
indoor units, outdoor units, and
Signal amplifiers
Measure the resistance of the Signal
amplifier terminal and the terminal of
the indoor and outdoor units con-
nected farthest away from the device
where terminal resistor is measured.
A value from the table is displayed,
depending on the distance from the
Signal amplifier and the device where
the terminal resistor is set.
This value is an estimate.
(2) Transmission cable connecting out-
door units in a refrigerant system
The resistance between the terminals of
the transmission cable is 60 Ω ±15 Ω
.
This value is an estimate.
Distance from termination resistor
(m)
0~100 ~200 ~300 ~400 ~500
Approximate resistance (Ω)
0 ~
50
A short circuit somewhere or 2
or more termination resistors are
connected
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
~
Faulty contact or wiring length over
500 m
1K
~∞
Faulty contact, open circuit, or no
termination resistor
9. PIPE INSTALLATION II
Connection diagram for heat pump system
A) In case of connecting 1 outdoor unit
Outdoor unit
Pressure gauge
Vacuum pump
Scale
Pressure regulating valve
Nitrogen
Indoor unit
Indoor unit
B) In case of connecting multiple outdoor units
Outdoor unit Outdoor unit
Pressure gauge
Vacuum pump
Scale
Pressure regulating valve
Nitrogen
Indoor unit
Indoor unit
Connection diagram for heat recovery system
C) In case of connecting 1 outdoor unit
Outdoor unit
Pressure gauge
Vacuum pump
Scale
Pressure regulating valve
Nitrogen
Indoor unit
RB unit
D) In case of connecting multiple outdoor units
Outdoor unit Outdoor unit
Pressure gauge
Vacuum pump
Scale
Pressure regulating valve
Nitrogen
Indoor unit
RB unit
Valve opening and closing operation
Charging cap
Valve
Cap
Close
Hexagon
wrench
Close
Open
Open
Spindle
Table A (Tightening torque)
Valve type Spindle Cap Charging cap
Liquid
AOUA72/96
4.0 to 4.9 lbf·ft
(5.4 to 6.6 N·m)
10.0 to 12.2 lbf·ft
(13.5 to 16.5 N·m)
8.4 to 10.3 lbf·ft
(11.4 to 14.0 N·m)
AOUA120
6.0 to 7.3 lbf·ft
(8.1 to 9.9 N·m)
13.3 to 16.2 lbf·ft
(18.0 to 22.0 N·m)
AOUA144/
168/192
8.1 to 9.6 lbf·ft
(11.0 to 13.0 N·m)
16.6 to 20.3 lbf·ft
(22.5 to 27.5 N·m)Suction gas
19.9 to 24.3 lbf·ft
(27.0 to 33.0 N·m)
Gas/Discharge gas
9.1. Sealing test
CAUTION
Use only nitrogen gas.
Never use refrigerant gas, oxygen, in flammable gas or poisonous gas to pressurize the
system. (If oxygen is used, there is the danger of an explosion.)
Do not apply 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 the charging of the
refrigerant gas have been completed.
After connecting the pipes, perform a sealing test.
Recheck that the 3-way valve are closed before performing a sealing test.
Pour nitrogen gas through both the liquid pipe and the gas pipe.
Pressurize nitrogen gas to 4.2 MPa to perform the sealing test.
Check all flare connection areas 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
the pressure has not decreased.
* When the outdoor temperature changes 5 °C, the test pressure changes 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 blazing
After completing the sealing test, release the nitrogen gas from both valves.
Release the nitrogen gas slowly.
9.2. Vacuum process
CAUTION
Do not turn on the power unless all operations are complete.
If the system is not evacuated sufficiently, 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
refrigerant 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 specifically 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 might 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
(-100.7kPa) for an hour using the vacuum pump (vacuum process).
• If the pressure does not reach 500 microns (-100.7kPa) even after depressurizing
for at least 2 hours, repeat the vacuum breakdown - vacuum process perform triple
evacuation procedure as necessary to bring the vacuum down to 500 microns
(-100.7kPa) 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.
9.2.1 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 (-100.7kPa). 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 (-100.7kPa).
(6) Remove the charging hose and reinstall the charging cap.
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