Daikin VRV W T-Series Installation Manual

Also see for RWEQ120TAYCU: Operation manual Installation manual

Contents

9 Maintenance and serviceInstallation manual44RWEQ96~432TAYCUVRV W T-Series water-cooled system air conditioner4P540122-1B – 2018.119 3 Maintenance of the plate heatexchangerThe performance of a plate heat exchanger may decline due to scaleaccumulation. It may be damaged by freezing due to the decrease inthe flow rate. For this reason, it is necessary to carry outprogrammed maintenance at regular intervals in order to preventscale.9 3 1 Daily service and maintenance1 Management of water qualityThe plate-type heat exchanger has a structure that does notpermit dismantling and cleaning, or replacing any parts. Pleasepay attention carefully to the quality of water to be used for theplate-type heat exchanger in order to prevent corrosion andsticking of scale.The water to be used for the plate-type heat exchanger shouldhave at least the quality as specified in the table of "4.4.1 Waterquality requirements" on page 15.When using any corrosion prevention agent, scale depressantagent, etc., such agent should have no corrosive featuresagainst stainless steel and copper.2 Management of condenser water flow rateIf the condenser water flow rate is not enough, it will result infreezing damage to the plate-type heat exchanger. Check forany clogging of the strainer, any air being caught, any reductionin the flow rate due to failure of the circulation pump bymeasuring the temperature and pressure differences at the inletand outlet ports of the plate-type heat exchanger. If the ageddifference in the temperature or pressure has increased beyondthe proper range, the flow rate should have decreased. Stop theoperation and remove the cause before restarting the operation.3 Steps to be taken if a freeze-protection device is activatedIf the freeze-protection device is activated during operation, besure to remove the cause before restarting the operation. If thefreeze-protection device has been once activated, a partialfreezing has already occurred. If you restart the operationwithout removing the cause, the plate-type heat exchanger willbe closed and the ice cannot be melted, and in addition, thefreezing process will be repeated, resulting in any damage tothe plate-type heat exchanger, and this can lead to refrigerantleaking or water entering the refrigerant circuit.9 3 2 Maintenance of plate-type heat exchangerThe performance of a plate-type heat exchanger may decline due toscale accumulation. It may be damaged by freezing due to the dropof flow rate. For this reason, it is necessary to carry out programmedmaintenances at a regular interval in order to prevent the scale frombeing generated.1 Before entering the season for use, carry out the followinginspections:1) Conduct a water quality test and make sure that it is withinthe standard.2) Clean the strainer.3) Make sure that the flow rate is correct.4) Make sure that the operational conditions (pressure, flowrate, outlet temperature, etc.) are normal.2 Because the plate-type heat exchanger has a structure whichdoes not permit disassembling and cleaning, follow thefollowing procedures for cleaning:1) For maintenance purposes it is required to provide for aconnection port on the water inlet and on the water outlet.You must connect a circulation pump in between these 2connection ports when cleaning the plate-type heatexchanger with chemicals.For cleaning the scale in the plate-type heat exchanger it isrecommended to use a solution with 5% diluted formic, citric,oxalic, acetic or phosphoric acid.Never use hydrochloric, sulfuric or nitric acid because suchsolutions have a strong corrosive feature.2) Make sure to provide for a stop valve in front of that inletwater pipe connection port and for a stop valve after theoutlet water pipe connection port.3) Connect the piping for circulation of cleaning chemicals tothe inlet and outlet piping of plate-type heat exchanger. Fillthe cleaning solution of 122-144°F (50-62°C) for a while inthe plate-type heat exchanger. Then, circulate the cleaningsolution by a pump for 2-5 hours.The time for cleaning depends on the temperature ofcleaning 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 ofscale.4) After circulating the cleaning solution, discharge the solutionfrom the plate-type heat exchanger, fill the heat exchangerwith a solution of 1-2% sodium hydroxide (NaOH) or sodiumbicarbonate (NaHCO 3 ). Circulate this solution for 15-20minutes for neutralization purpose.5) After the process of neutralization has been completed, rinsethe inner part of the plate-type heat exchanger with careusing fresh and clean water.6) When using any cleaning agent sold in the market, check inadvance that such agent has no corrosive features againststainless steel and copper.7) For details of cleaning method, ask the manufacturer ofrelated cleaning agent.3 After cleaning has been completed, make sure that the unit canbe operated in a normal fashion.