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85
8. SYSTEM DESIGN GUIDE
WR2-Series-575V
5) Handling plate heat exchangers for heat-source units
<Designing the piping system>
Install a strainer (50 mesh or finer recommended) near the heat-source unit on the inlet side of the hot/cold water pipe
and cooling-water pipe (hereafter referred to as water pipes) to prevent an infiltration of foreign materials of solid nature,
such as dirt and sand, into the plate heat exchanger.
Depending on the water quality, scale may form inside plate heat exchangers. Plate heat exchangers must be
chemically cleaned regularly to remove scale formation. Install sluice valves on the water pipes, and provide ports for
connecting a pipe between the sluice valves and the heat-source unit for chemical cleaning.
On both the inlet and outlet sides of water pipes, provide a plug to remove trapped air and water (also to be used for
cleaning heat-source units and for purging water before a period of nonuse in winter or at the end of an air conditioning
season). Also, provide automatic air-vent valves where air is likely to be trapped (such as a pipe that runs vertically).
In addition to installing the above-mentioned strainers, install a cleanable strainer near the pump pipe inlet.
Keep the pipes properly insulated and take an appropriate measure against humidity to minimize heat loss and prevent
freeze damage in severe cold climate.
If the system is stopped during winter or at night in subfreezing temperatures, take appropriate measures to protect
pipes from freezing (i.e., pipe purging and use of water-circulation pump or heater) and prevent resultant damage to
the plate heat exchanger.
<Test run>
Before performing a test run, check that the piping system is properly installed, especially the strainers, air-vents,
automatic water-supply valves, expansion tanks, and systems.
After the pipe system is filled with water, first, operate the pump alone to check the system for trapped air and adjust
the water flow rate to prevent the plate heat exchanger from freezing. Take into consideration the water pressure loss
before and after each heat-source unit, and make sure the water flow rate falls within the design water flow rate range.
Stop the test run and correct any problems found, if any.
At the completion of a test run, check the strainer at the inlet pipe of the heat-source unit and clean it as necessary.
<Daily maintenance>
Controlling the water quality
Plate heat exchangers cannot be disassembled for cleaning and have no replaceable parts. Watch the water quality to
prevent corrosion and scale formation. The quality of the water to be used for plate heat exchangers must meet the
water quality guidelines JRA GL-02-1994 specified by Japan Refrigeration and Air conditioning Industry Association
(JRAIA). (Refer to 3) Water treatment and water quality control.)
Controlling the circulation water flow rate
Insufficient water rate will cause freeze damage to plate heat exchangers. Check for insufficient water flow caused by
clogged strainer, trapped air in the system, or malfunction of the circulation water pump. Flow rate can also be checked
by measuring the temperature or pressure difference between the inlet and outlet of plate heat exchangers.
If the temperature or pressure difference goes outside of the specified range, stop the operation, remove the cause of
the problem, and resume operation.
What to do when the freeze protection trips
If the freeze protection trips during operation, be sure to remove its cause before resuming operation. Tripped freeze
protection indicates that the system is partially frozen, and resuming operation without removing the cause of the
problem will result in freeze damage to plate heat exchangers and/or pipes as well as resultant refrigerant leaks and
infiltration of water into the refrigerant circuit.
P
Example piping system configuration
Heat-source unit
Air-vent plug
(also to be used for pipe cleaning)
Cleaning device
Sluice valve
To outlet
From inlet
Sluice valve
Strainer
Water-purge plug
(also to be used for pipe cleaning)
Plate
heat
exchanger
0000006382.BOOK 85 ページ ２０２１年７月１９日 月曜日 午後４時１４分
