HVAC NATE Heat Pump Correctly Answered!!

On an R-22 system, line diameters and lengths are typically specified for a vapor pressure drop that does not exceed what? - ANSWER6-7PSI or 6F What is the primary purpose of using flux when soldering copper or brass parts? - ANSWERPrevent Oxidation The water that results from a defrost cycle of an air to air heat pump(runoff) must? - ANSWERDrain off and away from the outdoor coil. Why must the runoff be drained off and away from the outdoor coil? - ANSWERExcessive ice can build up on the bottom of the coil and can reduce capacity. What is the component that reduces sound transmission and prevents water leaks of a package heat pump installed on a roof? - ANSWERCurb Gasket Why do you need to add a control for a heat pump indoor coil that is installed on a fossil fuel furnace? - ANSWERSo the heat pump and furnace do not operate at the same time in normal heating. What happens when you energize a hermetic refrigeration compressor and the system is in a deep vacuum? - ANSWERMotor windings could become damaged. What needs to happen in order to consider an evacuation to be complete? - ANSWERSystem should be evacuated to a vacuum of 500 Microns or below. A system is supplied from the factory with charge for a 15 foot line set. The data plate shows the required system charge to be 5 pounds 10 ounces. The line set uses a 3/8 inch liquid line and is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigerant to be added for each added foot of refrigerant line length. How much refrigerant is needed to completely charge the system? - ANSWER6lbs Where are drive slips typically installed? - ANSWEROn the shorter sides of rectangular duct. What is a necessary check to properly set a heat anticipator? - ANSWERHeating control circuit amperage draw. A heat pump operating in normal ice free conditions maintains a certain temperature difference between the outdoor coil temperature and the surrounding outdoor ambient. What is this temperature referred to as? - ANSWERCoil TD. What is the smallest refrigerant leak that an electronic leak detector should be capable of sensing? - ANSWER.o5oz per year. When checking the pressures in an operating system with a manifold gauge set, will refrigerant oil in a hose will have an effect on the gauge? - ANSWERNo What is the absolute pressure at sea level if a gauge pressure is 35 psig? - ANSWER49.7psia 100,000 BTUH output furnace. Return air temp is 65F. Supply air is 135F. What is the CFM? - ANSWER1323CFM What is the best method of repair when a residential supply diffuser is noisy because of a loose vane? - ANSWERReplace the diffuser. When performing preventive maintenance on a heat pump what should the technician check and why? - ANSWEROutdoor fan. To be certain it runs freely with no binding. What is the effect of 170 volts supplied to a 208/230 volt compressor? - ANSWERWould cause the current to increase and the motor may trip on overload. On a service call for a cooling problem with a heat pump, your inspections find a liquid line that has condensation on it. What is most likely to cause this? - ANSWERRestriction in the liquid line. What is a reason for cool air complaints when a heat pump is operating in the heating cycle? - ANSWERExcessive supply air velocities. The following measurements are recorded on an operating heat pump system. The heat pump is operating with the compressor only with no auxiliary heat: • Heat pump only supply air temperature 92°F • Heat pump only return air temperature 70°F • Outdoor temperature 54°F • Supply air temp. /auxiliary heat ON 115°F • Return air temp. /auxiliary heat ON 70°F • CFM 1228 What is the heating capacity in BTUH? - ANSWER29,177 BTU/H Inadequate heating can be caused by what? - ANSWERDirty or clogged air filter. To minimize noise problems in residential duct systems, what is the range (recommended to maximum) of design air velocity in the rectangular main supply trunk? - ANSWER700 to 900 fpm conditions while checking a packaged heat pump in cooling. • The unit has a piston type metering device on both the indoor and outdoor coils. • Outdoor temperature 75°F • Superheat 55°F What is wrong with the system? - ANSWERUndercharged. What will you get when a capillary tube is overcharged? - ANSWERlow superheat and high sub cooling What is the effect of a low charge on the switchover operations of a reversing valve? - ANSWERReversing valves are less likely to transfer if charge is low. A technician is working on a heat pump with a capacitor start-capacitor run compressor. On initial startup, the compressor hums momentarily and the shuts down on internal overload. What is the problem? - ANSWERToo great a pressure difference on the compressor. A step down transformer has a rating of 40 VA. Its primary voltage is 120V with a secondary voltage of 24V. What is the maximum current draw of a load connected to this transformer? - ANSWER1.7amps What does a bright red or orange glow from the resistance element in a duct heater indicate? - ANSWERFlow of air is insufficient. What does the outdoor fan do during defrost on a heat pump and why? - ANSWERThe fan stops to minimize defrost time. What do bent vanes on a direct drive blower wheel in an air handler cause? - ANSWERLoss in air flow, excessive motor wear, and increased noise. A split system heat pump is using thermostatic expansion valves. The system performs properly in heating but in cooling the compressor pumps down. What could this mean? - ANSWERThe power element of the indoor expansion valve has lost its charge. What condition can cause a reduction from design capacity in a heat pump? - ANSWERUndersized vapor line. What is the result of excessive liquid line length or lift? - ANSWERFlash gas. What symptom could a technician expect on a heat pump system in the cooling mode if the check valve is leaking internally? - ANSWERFlooding of the indoor coil. Voltage across a closed contact in a 24V control circuit could indicate what? - ANSWERPitted or dirty contacts. What two checks typically made first on an electronic control? - ANSWERProper input voltage and proper output voltage. In a low voltage circuit, what does a corroded wire-to-terminal connection acts like? - ANSWERAn additional resistor. How should you test the continuity of a fuse? - ANSWERPower off, fuse removed What is the first check made for most electrical troubleshooting? - ANSWERVoltage check of the supply line. The following conditions exist in a circuit that supplies power to three parallel loads. One load is resistive One load is capacitive One load is inductive How do you find the total current? - ANSWERThe sum of the currents through each load. The technician is using an analog multimeter to check a run capacitor. With the meter set to ohms the needle swings toward zero and then slowly rises toward infinity. What does this tell the technician? - ANSWERThe capacitor charges and discharges. When should a technician test a hermetic compressor for a permanently open internal overload protector? - ANSWERWhile its cool. What is defined as two or more switch contacts connected in a circuit, or set of circuits, to control a load? - ANSWERControl String In order to troubleshoot a load controlled by a control string, what should the technician check first? - ANSWERProper voltage applied across the load. The technician suspects that an outdoor thermostat used to bring on auxiliary heat may be out of calibration. The thermostat is a close-on-fall type that is adjustable. What is one method for checking the thermostat calibration? - ANSWERManually rotate the shaft until the thermostat closes and compare the dial setting to an accurate outdoor temperature reading plus 10°F When must the installer must be certain to plumb the cabinet so its sides are vertical? - ANSWERWhen changing out an evaporator coil. What is the recommended maximum external static pressure used for heating and cooling equipment with blowers for 5 ton of cooling or less? - ANSWER0.1 in W.C When a balancing check of a newly installed duct what needs to happen? - ANSWERDampers should be open completely in all rooms. Why is operating sound is a consideration in the location of a condensing unit? - ANSWERBecause excessive noise could be disruptive to the customer A technician has determined a supply in a flexible duct system is leaking. What should be checked? - ANSWERAll connections inner and outer layers. What is sensible heat ratio? - ANSWERsensible removed ÷ total heat removed Service site conditions are: • House feels "drafty" in cooling • 3½ ton split system • High supply face velocities • Ductwork is properly sized • Total CFM 1400 What does this indicate? - ANSWERThese readings indicate the system is operating normally but the supply registers are too restrictive When a wet bulb reading is very close to the dry bulb reading from the same instrument, what does this indicate? - ANSWERRelative humidity is high. What measurements would be needed to properly evaluate a complaint of "drafty" operation with a heating system? - ANSWERSystem TD, Drop, and Static Pressure What kind of energy does the condenser remove from the refrigerant? - ANSWERSensible heat and Latent heat Where does refrigerant boil? - ANSWERIn the Evaporator.