Mitsubishi Electric PQHY-P250YHM-A Data Book Download Page 51

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3. 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 below.

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)

(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
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 recommended to
keep water quality. However, in the case that an open type
cooling tower is employed or the circulating water quality is in-
ferior, 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 in-
dustry (Japan Refrigeration, Air Conditioning Industry Associ-
ation, in case of Japan) for water treatment to be applied.
In order to keep the water quality within such standards, you
are kindly requested to conduct bleeding-off by overflow and
periodical water quality tests, and use inhibitors to suppress
condensation or corrosion. Since piping may be corroded by
some kinds of inhibitor, consult an appropriate water treatment
expert for proper water treatment.

Installation example of heat source unit

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

)

Acid consumption (pH4.8)

(mg CaCO