Mitsubishi Electric PLFY-WP VBM-E, Data Book

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3. SYSTEM DESIGN GUIDE
WR2
MEE15K052
3-2. Water piping work
Installation example of heat source unit
Although the water piping for the HYBRID CITY MULTI WR2 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 equip-
ment.
• 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.
Wrap the joint with sealing tape in the direction of the
threads (clockwise), and do not let the tape run over the
edge.
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.
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 HYBRID
CITY MULTI WR2 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 insula-
tion 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
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 HYBRID
CITY MULTI WR2 system, employment of the closed type
is recommended 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.
a)
b)
c)
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
4
2-
/ )
Acid consumption (pH4.8)
(mg CaCO
3
/ )
Total hardness (mg CaCO
3
/ )
Calcium hardness (mg CaCO
3
/ )
Ionic silica (mg SiO
2
/ )
Iron (mg Fe/ )
Copper (mg Cu/ )
Sulfide ion (mg S
2-
/ )
Ammonium ion (mg NH
4
+
/ )
Residual chlorine (mg Cl/ )
Free carbon dioxide (mg CO
2
/ )
Ryzner stability index
Standard
items
Refer-
ence
items
Items
Lower mid-range
temperature water system
7.0 ~ 8.0
30 or less
[300 or less]
50 or less
50 or less
50 or less
70 or less
50 or less
30 or less
1.0 or less
1.0 or less
not to be
detected
0.3 or less
0.25 or less
0.4 or less
–
7.0 ~ 8.0
30 or less
[300 or less]
50 or less
50 or less
50 or less
70 or less
50 or less
30 or less
0.3 or less
0.1 or less
not to be
detected
0.1 or less
0.3 or less
4.0 or less
–
Tendency
Recirculating
water
[68<T<140°F]
[20<T<60°C]
Make-up
water
Corrosive
Scale-
forming
Reference : Guideline of Water Quality for Refrigeration and Air Conditioning
Equipment. (JRA GL02E-1994)
Shutoff
valve
Main circulating
water pipe
Water inlet (lower)
Water outlet
(upper)
Drain pipe
Refrigerant
pipes
Shutoff valve
Y-type
strainer
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