92 8 outline a method of isolating an electrical

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92-8)Outline a method of isolating an electrical fault using the process of elimination. Check Line Voltage to the Unit Check Control Voltage Check Voltage to the non functional component Check Circuit to the non-functional Component 92-9)Describe the process of hop scotching. This technique works by starting at a point where there is correct voltage, and moving one lead from point to point in the circuit towards the non-functional load until the voltage is lost. 92-10)Using the logic flowchart in Figure 92-18, what is the first condition listed to check for a compressor that will not run when the contactor is closed? Loose or Open leads in compressor circuit 92-11)Using the troubleshooting systems list in Figure 92-19, what possible causes are listed for a unit which experiences high pressure switch tripping only during the cooling cycle? Inadequate GPM (water flow) Water too hot 92-12)Using the chart in Figure 92-20, what conditions cause both lights to display an alternating fast flash? Improper main ground; Broken igniter; OR: Open igniter circuit; Line voltage below 75 volts. 92-13)Using the air source heat pump sequence chart in Figure 92-2, list the devices in order that control the outdoor fan. R control power to thermostat Y Compressor Evaporator Float Switch Liquid Low Pressure Switch High Pressure Switch Anti short cycle timer Compressor Contactor Defrost Control Run Capacitor
279 92-14)Using the chart in Figure 92-17, what problems can cause both a high superheat and a high subcooling? Liquid Restriction Underfeeding metering device Low Capacity Compressor 92-15)Using the induced draft sequence chart in Figure 92-4, what should be checked if the induced draft fan comes on but the igniter is never energized? Check to see if the vent has the correct draft Check for obstructions in the vent Check the draft pressure switch 92-16)List some resources the air conditioning technician can use to learn about the system operational sequence. Sources of information on the system sequence of operation include the manufacturer’s installation and operation and manuals, unit wiring diagrams, unit charging charts, and general textbooks. 92-17)List some sources the air conditioning technician can use to get system operational data. Sources for the current system operational data include the homeowner, general observation, diagnostic boards, and system performance tests. 92-18)Using Figure 92-7, what should the approximate suction pressure be for an EC015 system operating in heating with an entering water temperature of 50°F and a water flow of 2.8 GPM? 164 – 201 psig 92-19)Why are diagnostic codes not always able to identify the system problem? On board diagnostics can only report issues that it has inputs for. 92-20)Why should service technicians be familiar with company pricing policies?

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