In a residential air conditioning system, where does the refrigerant absorb heat from the conditioned space?
Ac Theory Refrigerant Flow
Question · Easy
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Short
Which component of the refrigeration cycle changes high-pressure liquid into low-pressure liquid/vapor just before the evaporator?
Passage that carries air; how much it moves depends on opening size, layout resistance and air speed.
System components
Guess the Term
The four major components of the basic vapor-compression refrigeration cycle are the compressor, condenser, metering device, and:
Read the clue and guess the term in 6 tries.
Game
What is the term for the heat added to a vapor above its saturation (boiling) temperature at a given pressure?
Superheat Subcooling Charging
Chamber in an air handler where outdoor air and return air are blended.
A system uses a fixed orifice (piston) metering device. Which measurement is the correct method to verify the refrigerant charge?
Question · Medium
A system uses a thermostatic expansion valve (TXV). Which measurement is the correct method to verify the refrigerant charge?
To flow nitrogen through tubing while it is being joined, preventing oxidation inside.
Installation and startup
Subcooling is calculated by taking the saturated liquid temperature (from the P/T chart for the high-side pressure) and:
Swap tiles to line up three of the same term.
Term Match
On an R-410A system the high-side gauge reads 365 psig and the P/T chart shows that pressure corresponds to a saturated temperature of about 110 degrees F. The liquid line measures 98 degrees F. What is the subcooling?
Heat exchanger placed in the airstream to warm or cool air delivered to a space.
During service, you measure high superheat and low subcooling on a TXV system. What is the most likely cause?
Diagnostics Troubleshooting
A technician finds low suction pressure, high superheat, and low subcooling, but the metering device and airflow check out. What should be done next?
Metering device used in a system whose charge is set by subcooling; poor bulb contact with the suction line can cause a misdiagnosis.
Which symptom set most strongly indicates a dirty or airflow-restricted condenser coil?
Flip two cards at a time to find matching terms.
Term Pairs
A capacitor-start compressor will not run and hums, then trips on its internal overload. The capacitor tests open. What is the correct repair?
Electrical Controls
Higher-efficiency blower type that varies speed and torque to hold airflow as pressure rises.
The standard control transformer voltage used for residential HVAC low-voltage thermostat circuits is:
Which thermostat terminal energizes the compressor contactor for cooling?
Common blower type in furnaces and air handlers; it runs at a fairly fixed speed and delivers less air as resistance rises.
A run capacitor is rated 35/5 uF 440V. What does the '5' designate?
Find five hidden terms in a grid of letters.
Term Search
Before recovering refrigerant, EPA Section 608 requires the technician to be certified. Which certification type covers servicing high-pressure appliances such as residential split-system AC?
Refrigerant Recovery Epa 608
Kind of filter ___ that must be replaced when a system is opened; it removes moisture, acid and particles from the refrigerant.
Under EPA 608, what is the required recovery vacuum level for a high-pressure appliance containing less than 200 pounds of refrigerant when using recovery equipment manufactured on or after November 15, 1993?
Question · Hard
Releasing (venting) HCFC and HFC refrigerants such as R-22 and R-410A to the atmosphere during service is:
Amount of refrigerant in a system; too little can cause ice on the evaporator and too much can slug the compressor.
Service diagnostics
A compressor draws locked-rotor amperage and trips the breaker immediately on start, and an ohmmeter shows continuity from a motor terminal to the compressor shell. The most likely diagnosis is:
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Which device protects the compressor by interrupting the circuit when discharge pressure becomes dangerously high?
Condition of low pressure a system is pulled to before charging; a rise above 500 microns after 10 minutes means more is needed.
On an operating system, a low-side gauge connected to the suction service port reads the:
What is the primary function of the suction line accumulator on an air conditioning or heat pump system?
Components
Refrigerant escape detected by pressurizing a system with nitrogen; the system should hold 150 psig for 10 minutes.
A liquid line filter-drier has become restricted. What temperature symptom would help confirm this restriction?
Noncondensable gases (such as air) trapped in the high side of a refrigeration system will cause:
Kind of pressure that measures a fan's resistance to moving air, in inches of water column.
When recovering refrigerant into a recovery cylinder, the cylinder should never be filled beyond what percentage of its capacity to allow for liquid expansion?
A residential split system has a low-pressure switch open. Suction pressure is near zero and the system has lost most of its charge. After leak repair and recovery of any remaining refrigerant, what must be done before recharging?
Instrument with manifold hoses that connects to service ports to read high- and low-side pressures.
What micron level is generally accepted as an adequate deep vacuum, indicating the system is dry and free of noncondensables before charging?
The condenser split is defined as the difference between the condensing temperature and the:
Unit used to state the volume of air a fan moves; performance pairs it with a resistance or pressure.
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