Maintenance Of The Plate Heat Exchanger; Daily Service And Maintenance; Maintenance Of Plate-Type Heat Exchanger - Daikin VRV W T-Series Installation Manual

9 Maintenance and service
9 .3 Maintenance of the plate heat
exchanger
The performance of a plate heat exchanger may decline due to scale
accumulation. It may be damaged by freezing due to the decrease in
the flow rate. For this reason, it is necessary to carry out
programmed maintenance at regular intervals in order to prevent
scale.
9 .3 .1

Daily service and maintenance

1 Management of water quality
The plate-type heat exchanger has a structure that does not
permit dismantling and cleaning, or replacing any parts. Please
pay attention carefully to the quality of water to be used for the
plate-type heat exchanger in order to prevent corrosion and
sticking of scale.
The water to be used for the plate-type heat exchanger should
have at least the quality as specified in the table of "4.4.1 Water
quality requirements" on page 15.
When using any corrosion prevention agent, scale depressant
agent, etc., such agent should have no corrosive features
against stainless steel and copper.
2 Management of condenser water flow rate
If the condenser water flow rate is not enough, it will result in
freezing damage to the plate-type heat exchanger. Check for
any clogging of the strainer, any air being caught, any reduction
in the flow rate due to failure of the circulation pump by
measuring the temperature and pressure differences at the inlet
and outlet ports of the plate-type heat exchanger. If the aged
difference in the temperature or pressure has increased beyond
the proper range, the flow rate should have decreased. Stop the
operation and remove the cause before restarting the operation.
3 Steps to be taken if a freeze-protection device is activated
If the freeze-protection device is activated during operation, be
sure to remove the cause before restarting the operation. If the
freeze-protection device has been once activated, a partial
freezing has already occurred. If you restart the operation
without removing the cause, the plate-type heat exchanger will
be closed and the ice cannot be melted, and in addition, the
freezing process will be repeated, resulting in any damage to
the plate-type heat exchanger, and this can lead to refrigerant
leaking or water entering the refrigerant circuit.
Installation manual
44
9 .3 .2

Maintenance of plate-type heat exchanger

The performance of a plate-type heat exchanger may decline due to
scale accumulation. It may be damaged by freezing due to the drop
of flow rate. For this reason, it is necessary to carry out programmed
maintenances at a regular interval in order to prevent the scale from
being generated.
1 Before entering the season for use, carry out the following
inspections:
1) Conduct a water quality test and make sure that it is within
the standard.
2) Clean the strainer.
3) Make sure that the flow rate is correct.
4) Make sure that the operational conditions (pressure, flow
rate, outlet temperature, etc.) are normal.
2 Because the plate-type heat exchanger has a structure which
does not permit disassembling and cleaning, follow the
following procedures for cleaning:
1) For maintenance purposes it is required to provide for a
connection port on the water inlet and on the water outlet.
You must connect a circulation pump in between these 2
connection ports when cleaning the plate-type heat
exchanger with chemicals.
For cleaning the scale in the plate-type heat exchanger it is
recommended to use a solution with 5% diluted formic, citric,
oxalic, acetic or phosphoric acid.
Never use hydrochloric, sulfuric or nitric acid because such
solutions have a strong corrosive feature.
2) Make sure to provide for a stop valve in front of that inlet
water pipe connection port and for a stop valve after the
outlet water pipe connection port.
3) Connect the piping for circulation of cleaning chemicals to
the inlet and outlet piping of plate-type heat exchanger. Fill
the cleaning solution of 122-144°F (50-62°C) for a while in
the plate-type heat exchanger. Then, circulate the cleaning
solution by a pump for 2-5 hours.
The time for cleaning depends on the temperature of
cleaning solution or the degree of scale accumulation.
Therefore, please watch the change of the dirtiness (color)
of cleaning solution to determine the level of removal of
scale.
4) After circulating the cleaning solution, discharge the solution
from the plate-type heat exchanger, fill the heat exchanger
with a solution of 1-2% sodium hydroxide (NaOH) or sodium
bicarbonate (NaHCO ). Circulate this solution for 15-20
3
minutes for neutralization purpose.
5) After the process of neutralization has been completed, rinse
the inner part of the plate-type heat exchanger with care
using fresh and clean water.
6) When using any cleaning agent sold in the market, check in
advance that such agent has no corrosive features against
stainless steel and copper.
7) For details of cleaning method, ask the manufacturer of
related cleaning agent.
3 After cleaning has been completed, make sure that the unit can
be operated in a normal fashion.
VRV W T-Series water-cooled system air conditioner
RWEQ96~432TAYCU
4P540122-1B – 2018.11