Carrier 30RBM 160 Installation, Operation And Maintenance Instructions

Also see for 30RBM 160: Installation, operation and maintenance instructions

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Carrier 30RBM 160 Installation, Operation And Maintenance Instructions Manual pdf 32 page image

329 - NOMINAL SYSTEM WATER FLOW RATE CONTROLRefer to the schematic diagram in the "Water connections"paragraph for all item references in this chapter.The water circulation pumps of the units in the range have beensized to allow the hydronic modules to operate in all possibleconfigurations based on the specific system conditions, i.e. at arange of temperature differences between the water inlet andoutlet at full load from 3 to 10 K.This temperature difference required between the water inletand outlet determines the nominal flow rate of the system. Usethe specification provided when selecting the unit to determinethe system's operating conditions.In particular, collect the data to be used for setting theinstallation flow rate:• For a unit without hydronic module: nominal pressuredrop at the unit terminals (plate heat exchanger + internalwater pipe). This is measured with pressure differentialgauges that must be installed at the unit's inlet and outlet(item 21).• Units with fixed speed pumps: nominal flow rate. Thepressure of the fluid is measured by sensors installed atthe inlet of the pump and outlet of the unit (items 7 and10). The system calculates the flow rate associated withthis differential pressure. The flow rate can be read directlyon the user interface (refer to the control manual for therange).• Units with variable speed pumps - control on pressuredifferential: pressure differential at the hydronic moduleterminals,• Units with variable speed pumps - control on temperaturedifference: nominal temperature delta at the exchanger.If this information is not available when activating the system,contact the design office responsible for the installation toobtain it.This data can be obtained either from the performance tablesincluded in the technical documentation (for cases where thewater type heat exchanger temperature delta is 5 K) or fromthe "Electronic Catalogue" selection program for all otherapplicable temperature delta in the range of 3 to 10 K.9.1 - Units without hydronic moduleGeneral informationThe nominal flow rate of the system will be set using a manualvalve that should be installed on the water outlet pipe (item22 on the water circuit schematic diagram).Due to the pressure drop it generates on the hydronic network,this flow control valve is used to set the network pressure/flowrate curve to the pump pressure/flow rate curve, to obtain thenominal flow rate at the desired operating point.This is checked by reading the pressure drop on the unit (plateheat exchanger + internal piping).As the exact total system pressure drop is not known uponcommissioning, it is necessary to adjust the water flow ratewith the control valve to obtain the installation's specific flowrate.Hydronic circuit cleaning procedure• Open all control valves completely (item 22).• Start up the system pump.• Read the pressure drop of the plate heat exchanger usingthe pressure differential gauge to find the differencebetween the unit inlet and outlet (item 21).• Let the pump run for 2 hours continuously to clean upthe system's hydraulic circuit (presence of contaminatingsolids).• Perform another reading.• Compare this value to the initial value.• A reducing value of the flow indicates that the filters onthe system need to be removed and cleaned. In this case,close the shut-off valves on the water inlet and outlet(item 19) and remove the filters (items 20 and 1) afterdraining the hydronic part of the unit (items 6).• Remove the air from the circuit (items 5 and 17).• Repeat until all fouling is removed from the filter.Water flow rate adjustment procedureOnce the circuit has been decontaminated, read the pressureson the pressure gauges (water inlet pressure - outlet pressure)to determine the pressure drop across the unit terminals (plateheat exchanger + internal pipework).Compare the value obtained with the design value predictedby the selection software.If the pressure drop reading is above the specified value, thisindicates that the flow rate at the terminals of the unit (andtherefore within the system) is too high. In this case, close thecontrol valve and read the new difference in pressure.Repeat as necessary, closing the control valve until the specificpressure drop corresponding to the unit's nominal flow rateis achieved.NOTE:If the network has an excessive pressure drop in relation tothe available static pressure delivered by the system's pump,the nominal water flow rate cannot be obtained (lowerresulting flow rate) and the temperature difference betweenthe water inlet and outlet of the water type heat exchangerwill be increased.To reduce the system's hydronic network pressure drop:• Reduce the pressure drops of individual components(bends, level changes, options, etc.) as much as possible;• Use the correct pipe diameter;• Do not extend the hydronic systems.