Carrier AQUAFORCE 30XA080-500 Controls, Start-up, Operation, Service And Troubleshooting Instructions

Also see for AQUAFORCE 30XA080: Installation instructions Controls, start-up, operation, service and troubleshooting instructions Installation instructions Product data

Contents

Carrier AQUAFORCE 30XA080-500 Controls, Start-up, Operation, Service And Troubleshooting Instructions Manual pdf 76 page image

76ECONOMIZER EXV CONTROL — The economizer EXVis controlled by the circuit EXV board. There is an economizergas temperature thermistor and economizer pressure transducerlocated in the line, which runs from the economizer assembly tothe compressor. The economizer pressure is converted to satu-rated temperature and is used to calculate economizer superheat.Economizer superheat equals economizer temperature minussaturated economizer temperature. The economizer EXV onlyoperates during normal conditions when the capacity of thecircuit is greater than 75%. Once the capacity of the circuit isgreater than 75% the MBB will start controlling the economizerEXV to maintain economizer superheat set point, which is ap-proximately 8° to 12° F (4.4° to 6.7° C). If the circuit capacity isless than 75%, the economizer EXV will be closed.The economizer EXV has one override. If the discharge gastemperature exceeds 195 F (90.6 C) the economizer EXV willstart to open. The EXV will be controlled to maintain dischargegas temperature at approximately 195 F (90.6 C).If it appears that main EXV or economizer EXV is notproperly controlling circuit operation to maintain correct super-heat, there are a number of checks that can be made using testfunctions and initialization features built into the microproces-sor control. See the Service Test section to test EXVs.EXV TROUBLESHOOTING PROCEDURE — There aretwo different economizer EXVs. Both of the economizerEXVs have a total of 2785 steps. There are three different mainEXVs, which all have a total of 3690 steps. The EXV motormoves at 150 steps per second. Commanding the valve toeither 0% or 100% will add an additional 160 steps to themove, to ensure the valve is open or closed completely.Follow the steps below to diagnose and correct EXVproblems. Check EXV motor operation first. Switch theEnable/Off/Remote (EOR) Contact switch to the Off position.Check the appropriate circuit EXV, Circuit A EXV % Open(Circuit A EXV Position, EXV.A), Circuit B EXV % Open(Circuit B EXV Position, EXV.B), or Circuit C EXV % Open(Circuit C EXV Position, EXV.C). The current value of 0 willbe displayed. Increase the EXV position to select 100% valveposition. The actuator should be felt moving through the EXV.To close the valve, select 0%. The actuator should knock whenit reaches the bottom of its stroke. See Table 48 for a list ofEXV modes and submodes.If the valve is not working properly, continue with the fol-lowing test procedure:Check the 8-position DIP switch on the board for the properaddress (see page 11). Check the EXV output signals at appro-priate terminals on the EXV module. For 30XA080 units,connect the positive test lead to EXV-J2A terminal 5 for CircuitA and to EXV-J2B terminal 5 for Circuit B.For 30XA090-500 units connect positive test lead toEXV(X)-J2A terminal 5 for EXV(X) and EXV(X)-J2B termi-nal 5 for Economizer EXV(X). Using the Service Test proce-dure on page 105, move the valve output under test to 100%.DO NOT short meter leads together or pin 5 to any other pin,as board damage will occur. During the next several seconds,carefully connect the negative test lead to pins 1,2,3 and 4 insuccession. Digital voltmeters will average this signal anddisplay approximately 6 vdc. If the output remains at a constantvoltage other than 6 vdc or shows 0 volts, remove the connec-tor to the valve and recheck.Select 0% to close the valve.NOTE: Twelve vdc is the output from the EXV board whenthe valve is stationary.See Tables 6 and 7. If a problem still exists, replace theEXV board. If the reading is correct, the expansion valve andEXV wiring should be checked. Check the EXV connector andinterconnecting wiring.1. Check color-coding and wire connections. Make surethey are connected to the correct terminals at the EXVboard and EXV plug and that the cables are not crossed.2. Check for continuity and tight connection at all pinterminals.Check the resistance of the EXV motor windings. For30XA080,082 units remove the EXV module plug EXV-J2Afor Circuit A EXV and EXV-J2B for Circuit B EXV. For30XA090-500 units remove the EXV module plug EXV(X)-J2A for main EXV and EXV(X)-J2B for economizer EXV.Check the resistance of the two windings between pins 1 and 3for one winding and pins 2 and 4 for the other winding. Theresistance should be 52 ohms (± 5.2 ohms). Also check pins 1-4for any shorts to ground.Fig. 47 — Cutaway Views of the Electronic Expansion Valve1. Cable2. Glass Seal3. Motor Housing4. Stepper Motor5. Bearing6. Lead Screw7. Insert8. Valve Piston9. Valve Seat10. Valve Port a30-4241