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8. SYSTEM DESIGN GUIDE
8-2. Water piping work
Although the water piping for the CITY MULTI WY system does not differ from that for ordinary air conditioning systems,
pay special attention to the items below in conducting the piping work.
1) Items to be observed on installation work
• In order to equalize piping resistance for each unit, adapt
the reverse return system.
• Mount a joint and a valve onto the water outlet/inlet of the
unit to allow for maintenance, inspection and replacement
work. Be sure to mount a strainer at the water inlet piping of
the unit. (The strainer is required at the circulation water
inlet to protect the heat source unit.)
* The installation example of the heat source unit is shown
right.
• Be sure to provide an air relief opening on the water piping
properly, and purge air after feeding water to the piping
system.
• Condensate will generate at the low temperature part inside
the heat source equipment. Connect drain piping to the
drain piping connection located at the bottom of the heat
source equipment to discharge it outside the equipment.
• At the center of the header of the heat exchanger water inlet
inside the unit, a plug for water discharge is being provided.
Use it for maintenance work or the like.
• Mount a backflow prevention valve and a flexible joint for
vibration control onto the pump.
• Provide a sleeve to the penetrating parts of the wall to
prevent the piping.
• Fasten the piping with metal fitting, arrange the piping not to
expose to cutting or bending force, and pay sufficient care
for possible vibration.
• Be careful not to erroneously judge the position of the inlet
and outlet of water.
(Lower position : Inlet, Upper position : Outlet)
• When connecting heat source unit water piping and water
piping on site, apply liquid sealing material for water piping
over the sealing tape before connection. (for Maximum
water pressure above 1.0MPa)
• Wrap the sealing tape as follows.
a) Wrap the joint with sealing tape in the direction of the
threads (clockwise), and do not let the tape run over the
edge.
b) Overlap the sealing tape by two-thirds to three-fourths of its
width on each turn. Press the tape with your fingers so that
it is pressed firmly against each thread.
c) Leave the 1.5th through 2nd farthest threads away from the
pipe end unwrapped.
• Hold the pipe on the unit side in place with a spanner when
installing the pipes or strainer. Tighten screws to a torque of
150N
m.
•
2) Thermal insulation work
Thermal insulation or anti sweating work is not required for
the piping inside buildings in the case of the CITY MULTI
WY system if the operating temperature range of circulation
water stays within the temperature near the normal
(summer : 29.4°C[85°F], winter : 21.1°C[70°F]).
In case of the conditions below, however, thermal insulation
is required.
• Use of well water for heat source water
• Outdoor piping portions
• Indoor piping portions where freezing may be caused in
winter
• A place where vapor condensation may be generated on
MEE15K036
Installation example of heat source unit
Main circulating
water pipe
Shutoff
valve
piping due to an increase in dry bulb temperature inside the
ceiling caused by the entry of fresh outdoor air
• Drain piping portions
3) Water treatment and water quality control
For the circulation water cooling tower of the CITY MULTI
WY system, employment of the closed type is recom-
mended to keep water quality. However, in the case that an
open type cooling tower is employed or the circulating
water quality is inferior, scale will adhere onto the water
heat exchanger leading to the decreased heat exchange
capacity or the corrosion of the heat exchanger. Be
sufficiently careful for water quality control and water
treatment at the installation of the circulation water system.
• Removal of impurities inside piping
Be careful not to allow impurities such as welding fragment,
remaining sealing material and rust from mixing into the
piping during installation work.
• Water treatment
The water quality standards have been established by the
industry (Japan Refrigeration, Air Conditioning Industry
Association, in case of Japan) for water treatment to be
applied.
Items
pH (25°C[77°F])
Electric conductivity (mS/m) (25°C[77°F])
(μS/cm) (25°C[77°F])
Chloride ion
(mg Cl
Sulfate ion
(mg SO
Standard
4
Acid consumption (pH4.8)
items
(mg CaCO
Total hardness
(mg CaCO
Calcium hardness (mg CaCO
Ionic silica
(mg SiO
Refer-
Iron
(mg Fe/
ence
Copper
(mg Cu/
items
Sulfide ion
(mg S
Ammonium ion
(mg NH
Residual chlorine
(mg Cl/
Free carbon dioxide
(mg CO
Ryzner stability index
Reference : Guideline of Water Quality for Refrigeration and Air Conditioning
Equipment. (JRA GL02E-1994)
HEAT SOURCE
Shutoff valve
Y-type
strainer
Water outlet
(upper)
Refrigerant
Water inlet (lower)
pipes
Drain pipe
Lower mid-range
Tendency
temperature water system
Recirculating
water
Make-up
Scale-
Corrosive
[20<T<60°C]
water
forming
[68<T<140°F]
7.0 ~ 8.0
7.0 ~ 8.0
30 or less
30 or less
[300 or less]
[300 or less]
50 or less
-
/
)
50 or less
2-
/
)
50 or less
50 or less
50 or less
50 or less
/
)
3
/
)
70 or less
70 or less
3
/
)
50 or less
50 or less
3
30 or less
/
)
30 or less
2
0.3 or less
)
1.0 or less
)
1.0 or less
0.1 or less
not to be
not to be
2-
/
)
detected
detected
+
/
)
0.3 or less
0.1 or less
4
)
0.25 or less
0.3 or less
4.0 or less
/
)
0.4 or less
2
–
–
76
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