Panasonic U-4LE1E5 / U-4LE1E8 / U-5LE1E5 / U-5LE1E8 / U-6LE1E5 / U-6LE1E8 (serv.man2) Service Manual ▷ View online
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Design of Mini VRF SYSTEM
5. HOW TO PROCESS TUBING
5-2. Connecting Tubing Between Indoor and Outdoor Units
Fig. 2-27
Torque wrench
Spanner
Indoor unit
Outdoor unit
Because the pressure is approximately 1.6 times higher
than conventional refrigerant pressure, the use of ordinary
flare nuts (type 1) or thin-walled tubes may result in tube
rupture, injury, or asphyxiation caused by refrigerant
leakage.
In order to prevent damage to the flare caused by over-tightening of the flare nuts, use the table on this page as a guide
when tightening.
When tightening the flare nut on the liquid tube, use an adjustable wrench with a nominal handle length of 200 mm.
(1) Tightly connect the indoor-side refrigerant tubing extended
from the wall with the outdoor-side tubing.
(2) To fasten the flare nuts, apply specified torque as at right:
When removing the flare nuts from the tubing connections,
or when tightening them after connecting the tubing, be sure
to use 2 adjustable wrenches or spanners. (Fig. 2-27)
If the flare nuts are over-tightened, the flare may be damaged,
which could result refrigerant leakage and cause injury or
asphyxiation to room occupants.
For the flare nuts at tubing connections, be sure to use the flare nuts that were supplied with the unit, or else flare nuts for
R410A (type 2).
The refrigerant tubing that is used must be of the correct wall thickness as shown in the table above.
Tube diameter
Tightening torque
(approximate)
Tube thickness
ø6.35 (1/4")
14 – 18 N · m
{140 – 180 k
gf · cm}
0.8 mm
ø9.52 (3/8")
34 – 42 N · m
{340 – 420 k
gf · cm}
0.8 mm
ø12.7 (1/2")
49 – 55 N · m
{490 – 550 k
gf · cm}
0.8 mm
ø15.88 (5/8")
68 – 82 N · m
{680 – 820 k
gf · cm}
1.0 mm
ø19.05 (3/4")
100 – 120 N · m
{1000 – 1200 k
gf · cm}
1.2 mm
5-3. Insulating the Refrigerant Tubing
Tubing Insulation
Standard Selection of Insulation Material
Under the environment of the high temperature and high
humidity, the surface of the insulation material is easy to
become condesation. This will result in leakage and dew
drop. Refer to the chart shown below when selecting the
insulation material. In case that the ambient temperature and
relative humidity are placed above the line of the insulation
thickness, the condensation may occasionally make a dew
drop on the surface of the insulation material. In this case,
select the better insulation efficiency.
However, since the condition will be different due to
the sort of the insulation material and the environmental
condition of the installation place, see the chart shown
below as a reference when making a selection.
*
Standard Selection of Tubing Insulation
Calculating condition
Sort of insulation material
Polyethylene heat
resistingmaterial
resistingmaterial
Thermal conductivity
of insulation material
of insulation material
Based on JIS A9501
Calculating formula used
when calculating thickness
when calculating thickness
Based on JIS A9501
Refrigerant temperature
2°C
40
10
20
30
40
50
50
60
70
80
90
100
ø6.35
Ambient temperature [°C]
Thickness
30mm
Thickness
20mm
30mm
Thickness
20mm
Thickness
10mm
10mm
Ambient relative humidity [%]
10
20
30
40
50
40
50
60
70
80
90
100
ø9.52
Ambient temperature [°C]
Thickness
30mm
Thickness
20mm
30mm
Thickness
20mm
Thickness
10mm
10mm
Ambient relative humidity [%]
10
20
30
40
50
40
50
60
70
80
90
100
ø12.7
Ambient temperature [°C]
Thickness
30mm
Thickness
20mm
30mm
Thickness
20mm
Thickness
10mm
10mm
Ambient relative humidity [%]
10
20
30
40
50
40
50
60
70
80
90
100
ø15.88
Ambient temperature [°C]
Thickness
30mm
Thickness
20mm
30mm
Thickness
20mm
Thickness
10mm
10mm
Ambient relative humidity [%]
10
20
30
40
50
40
50
60
70
80
90
100
ø19.05
Ambient temperature [°C]
Thickness
30mm
Thickness
20mm
30mm
Thickness
20mm
Thickness
10mm
10mm
Ambient relative humidity [%]
Two tubes arranged together
Liquid tubing
Gas tubing
Insulation
Fig. 2-28
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Design of Mini VRF SYSTEM
5. HOW TO PROCESS TUBING
CAUTION
CAUTION
Fig. 2-31
Insulated tubes
Clamp
Drain hose
Apply putty here
Tubing
5-4. Taping the Tubes
(1)
(2)
(3)
At this time, the refrigerant tubes (and electrical wiring
if local codes permit) should be taped together with
armoring tape in 1 bundle. To prevent condensation from
overflowing the drain pan, keep the drain hose separate
from the refrigerant tubing.
Wrap the armoring tape from the bottom of the outdoor
unit to the top of the tubing where it enters the wall. As you
wrap the tubing, overlap half of each previous tape turn.
Clamp the tubing bundle to the wall, using 1 clamp approx.
each meter. (Fig. 2-31)
Do not wind the armoring tape too tightly since this will decrease
the heat insulation effect. Also ensure that the condensation drain
hose splits away from the bundle and drips clear of the unit and
the tubing.
If the exterior of the outdoor unit valves has been finished
with a square duct covering, make sure you allow sufficient
space to use the valves and to allow the panels to be
attached and removed.
Taping the flare nuts
Wind the white insulation tape around the flare nuts at the
gas tube connections. Then cover up the tubing connections
with the flare insulator, and fill the gap at the union with the
supplied black insulation tape. Finally, fasten the insulator at
both ends with the supplied vinyl clamps. (Fig. 2-29)
Fig. 2-29
Sealer (supplied)
Flare insulator (supplied)
Tube insulator
(not supplied)
Heat resistant
120°C or above
(not supplied)
Heat resistant
120°C or above
Vinyl clamps (supplied)
Flare nut
Unit side
insulator
insulator
Insulation tape (white)
(supplied)
(supplied)
Insulation material
The material used for insulation must have good insulation
characteristics, be easy to use, be age resistant, and must not
easily absorb moisture.
After a tube has been insulated,
never try to bend it into a narrow
curve because it can cause the
tube to break or crack.
Fig. 2-30
Refrigerant tubing and insulator (not supplied)
Drain pipe and insulator (not supplied)
Drain insulator
and clamp.
Large (supplied)
and clamp.
Large (supplied)
Packing clamp.
Small hose band
(supplied)
Small hose band
(supplied)
The procedure used for
installing the insulator
for both gas and liquid
tubes is the same.
installing the insulator
for both gas and liquid
tubes is the same.
Seal
Flare
insulator
insulator
Vinyl
clamp
clamp
Insulation
tape
tape
Never grasp the drain or refrigerant connecting
outlets when moving the unit.
N OT E
5-5. Finishing the Installation
After finishing insulating and taping over the tubing, use sealing
putty to seal off the hole in the wall to prevent rain and draft from
entering. (Fig. 2-32)
Fig. 2-32
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Design of Mini VRF SYSTEM
6. AIR PURGING
Fig. 2-34
Fig. 2-33
CAUTION
CAUTION
6. AIR PURGING
Manifold gauge
Vacuum pump
Outlet
Inlet
Air Purging with a Vacuum Pump (for Test Run) Preparation
Check that each tube (both liquid and gas tubes) between the
indoor and outdoor units has been properly connected and all
wiring for the test run has been completed.
Remove the valve caps from both the gas tube and liquid tube
service valves on the outdoor unit. Note that both liquid and
gas tube service valves on the outdoor unit are kept closed at
this stage. (Fig. 2-35)
Lo
Hi
Fig. 2-35
Manifold valve
Pressure
gauge
gauge
Cylinder
valve
valve
Nitrogen gas cylinder
(In vertical standing
position)
(In vertical standing
position)
Charge hose
Open
Close
Gas tube
Liquid tube
Outdoor unit
Close
Open
Service port ø7.94 mm
Air and moisture in the refrigerant system may have
undesirable effects as indicated below.
pressure in the system rises
operating current rises
cooling (or heating) efficiency drops
moisture in the refrigerant circuit may freeze and block
capillary tubing
water may lead to corrosion of parts in the refrigerant system
Therefore, the indoor unit and tubing between the indoor and
outdoor unit must be leak tested and evacuated to remove any
noncondensables and moisture from the system. (Figs. 2-33 and 2-34)
Leak test
(1)
Attach a manifold valve (with pressure gauges) and dry
nitrogen gas cylinder to this service port with charge
hoses.
Use a manifold valve for air
purging. If it is not available,
use a stop valve for this
purpose. The “Hi” knob of the
manifold valve must always be
kept closed.
(2)
Pressurize the system to no more than 3.80MPa with
dry nitrogen gas and close the cylinder valve when the
gauge reading reaches 3.80MPa. Then, test for leaks
with liquid soap.
To avoid nitrogen entering the
refrigerant system in a liquid
state, the top of the cylinder must
be higher than the bottom when
you pressurize the system.
Usually, the cylinder is used in a
vertical standing position.
(3)
Do a leak test of all joints of the tubing (both indoor and
outdoor) and both gas tube and liquid tube service valves.
Bubbles indicate a leak. Wipe off the soap with a clean cloth
after the leak test.
(4)
After the system is found to be free of leaks, relieve the
nitrogen pressure by loosening the charge hose connector
at the nitrogen cylinder. When the system pressure is reduced
to normal, disconnect the hose from the cylinder.
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Design of Mini VRF SYSTEM
6. AIR PURGING
Evacuation
CAUTION
CAUTION
N OT E
(1) Attach the charge hose end described in the preceding steps to
the vacuum pump to evacuate the tubing and indoor unit.
Confirm that the “Lo” knob of the manifold valve is open.
Then, run the vacuum pump. The operation time for evacuation
varies with the tubing length and capacity of the pump.
The following table shows the amount of time for evacuation:
Required time for evacuation
when 30 gal/min. vacuum pump is used
If tubing length is
less than 15 m
If tubing length is
longer than 15 m
45 min. or more
90 min. or more
The required time in the left
table is calculated based on the
assumption that the ideal
(or target) vacuum condition is
less than –101 kPa {–755 mmHg,
5 Torr}.
(2) When the desired vacuum is reached, close the “Lo” knob of the
manifold valve and turn off the vacuum pump. Confirm that the gauge
pressure is under –101 kPa {–755 mmHg, 5 Torr} after 4 to 5 minutes
of vacuum pump operation. (Fig. 2-36)
Use a cylinder designed for use with R410A
respectively.
Charging additional refrigerant
Charging additional refrigerant (calculated from the liquid tube
length as shown in Section 1-9 “Additional Refrigerant Charge”)
using the liquid tube service valve. (Fig. 2-37)
Use a balance to measure the refrigerant accurately.
If the additional refrigerant charge amount cannot be charged at
once, charge the remaining refrigerant in liquid form by using the
gas tube service valve with the system in cooling operation mode
at the time of test run. (Fig. 2-38)
Lo
Hi
Fig. 2-36
Open
Manifold valve
Pressure
gauge
Vacuum pump
Open
Close
Gas
tube
tube
Liquid
tube
tube
Outdoor unit
Close
Service port ø7.94 mm
Fig. 2-38
Open
Open
Gas
tube
tube
Liquid
tube
tube
Outdoor unit
Open
Close
Lo
Hi
Fig. 2-37
Manifold valve
Pressure
gauge
Valve
Close
Close
Gas
tube
tube
Liquid
tube
tube
Outdoor unit
Close
Liquid
R410A
Open
Finishing the job
(1)
(2)
With a hex wrench, turn the liquid tube service valve stem
counterclockwise to fully open the valve.
Turn the gas tube service valve stem counterclockwise to fully open
the valve.
To avoid gas from leaking when removing
the charge hose, make sure the stem of the
gas tube is turned all the way out.
(3)
(4)
(5)
Loosen the charge hose connected to the gas tube service port
(for ø 7.94 mm tube) slightly to release the pressure, then remove
the hose.
Replace the service port cap on the gas tube service port and fasten
the cap securely with an adjustable wrench or box wrench.
This process is very important to prevent gas from leaking from the
system.
Replace the valve caps at both gas tube and liquid tube service valves
and fasten them securely.
This completes air purging with a vacuum pump. The air conditioner is now
ready for a test run. Refer to Section “5. TEST RUN”.
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