Water Pipe Installation; Precautions During Installation; Insulation Installation; Water Processing And Water Quality Control - Mitsubishi Electric CITY MULTI PQRY-P250 Installationshandbuch

8. Water pipe installation

• City Multi WR2 Series pipes are similar to other air-conditioning pipes,
however, please observe the following precautions during installa-
tion.

8.1. Precautions during installation

• Use the reverse-return method to insure proper pipe resistance to
each unit.
• To insure easy maintenance, inspection, and replacement of the unit,
use a proper joint, valve, etc. on the water intake and outlet port. In
addition, be sure to install a strainer on the water intake pipe. (In
order to maintain the heat source unit, a strainer on the circulating
water inlet is necessary.)
* An example of the heat source unit installation is shown in the dia-
gram below.
• Install a suitable air vent on the water pipe. After sending water through
the pipe, be sure to vent the excess air.
• Compressed water may form in the low-temperature sections of heat
source unit. Use a drainage pipe connected to the drain valve at the
base of the unit to drain the water.
• There is a water vent plug in the center of the heat exchanger water
inlet head at the middle of the unit. Use this for maintenance, etc.
In addition, do not allow any of the unit's electrical parts (such as the
solenoid valve coil or compressor power supply) to become wet.
• Install a back flow-prevention valve on the pump and a flexible joint to
prevent excess vibration.
• Use a sleeve to protect the pipes where they go through a wall.
• Use metal fittings to secure the pipes, and install them so that they
have maximum protection against breakage and bending.
• Do not confuse the water intake and outlet valves.
• This unit doesn't have any heater to prevent freezing within tubes.
When the water flow is stopped on low ambient, take out the water
from tubes.
Example of heat source unit installation (using left piping)
D
B
A
C
G
F
H
A Water circulation pipe
B Close valve
C Close valve
D Water outlet
E Refrigerant piping
F Y-type strainer
G Water inlet
H Drain pipe
18
E

8.2. Insulation installation

With City Multi WR2 Series piping, as long as the temperature range of
the circulating water is kept to average temperatures year-round (30°C
in the summer, 20°C in the winter), there is no need to insulate or other-
wise protect indoor piping from exposure. You should use insulation in
the following situations:
• Any outdoor piping.
• Indoor piping in cold-weather regions where frozen pipes are a prob-
lem.
• When air coming from the outside causes condensation to form on
piping.
• Any drainage piping.
8.3. Water processing and water quality
control
To preserve water quality, use the closed type of cooling tower for WR2.
When the circulating water quality is poor, the water heat exchanger can
develop scales, leading to a reduction in heat-exchange power and pos-
sible corrosion of the heat exchanger. Please pay careful attention to
water processing and water quality control when installing the water cir-
culation system.
• Removal of foreign objects or impurities within the pipes.
During installation, be careful that foreign objects, such as welding
fragments, sealant particles, or rust, do not enter the pipes.
• Water Quality Processing
1 Depending on the quality of the cold-temperature water used in
the air-conditioner, the copper piping of the heat exchanger may
become corroded. We recommend regular water quality process-
ing.
Cold water circulation systems using open heat storage tanks
are particularly prone to corrosion.
2 For detailed water quality control methods and water quality cal-
culations, please refer to each regulation of the region.
(Ex. pH8.5 ~ 9.5 reference to CIBSE GUIDE)
3 Please consult with a water quality control specialist about water
quality control methods and water quality calculations before us-
ing anti-corrosive solutions for water quality management.
4 When replacing a previously installed air conditioning device (even
when only the heat exchanger is being replaced), first conduct a
water quality analysis and check for possible corrosion.
Corrosion can occur in cold-water systems even if there has been
no prior signs of corrosion.
If the water quality level has dropped, please adjust water quality
sufficiently before replacing the unit.

8.4. Pump interlock

The heat source unit may become damaged if it is operated with no
water circulating through the pipes.
Be sure to interlock unit operation and the water-circuit pump. Use the
terminal blocks for interlocking (TB8-3, 4) that can be found on the unit.
In the case of a pump interlock circuit signal connection to the TB8-3, 4,
remove the short-circuit wire. Also, to prevent mistaken error detection,
resulting from a poor connection, in the pressure valve 63PW, use a low
maintained current of 5mA or less.
TB8
3
A
4
A Short-circuit wire (Connected before delivery from manufacturer)
B Pump interlock circuit connection
63PW
B