Mechanical A/C Service Exam Flashcards
According to the ASHRAE refrigerant safety classification standard which designations would be the safest?
A-1
When transporting cylinders containing used refrigerant, DOT requires that you?
Attach DOT classification tags
What refrigeration compound have the highest ozone depletion potential (ODP)?
CFC’s
Approved refrigerant recovery cylinders can be identified by which color code?
Yellow tops and grey bodies
Under EPA’s regulations, what standard must reclaimed refrigerant meet before it can be resold?
ARI 700
The sate of refrigerant entering the compressor of a refrigeration system is ____.
low pressure vapor
Refrigerant that is cleaned using oil separation and single or multiple passes through devices, such as replaceable core filter-driers, which reduce moisture, acidity, and particulate matter is ____.
recycling
What leak detection method is most effective for locating the general are of a small leak?
Electronic leak detector
A compound pressure gauge for the low side of a system measures pressure in ____?
PSIG and inches of mercury
When first inspecting a hermetic system known to be leaking you should look for?
traces of oil
When charging a system with nitrogen ____?
only charge with nitrogen vapor and use a regulator
Refrigerant entering the thermal expansion device of an R-22 heat pump is ____.
saturated or sub-cooled high pressure liquid
Replacement of ____ is a repair which would always be considered major under EPA’s regulations.
an evaporator and condenser
At high temperatures R-12 and R-22 can decompose to form ____.
hydrochloric and hydrofluoric acid and phosgene gas
According to ASHRAE standard 15 a sensor and alarm are required for type A-1 refrigerants to sense ____.
oxygen deprivation
A ____ is not a method presently used for checking the fill level in a recovery tank.
sight glass
DOT Regulation 49 CFR requires that the ____ be recorded on the shipping paper for a hazard class 2.2 nonflammable compressed gases?
number of cylinders of each gas
What is not a standard recommended safe work practice when recovering refrigerants.
wearing a respirator when working with refrigerants
System dependent recovery equipment connote be used when?
the charge of the system is over 15 pounds
Reclamation of a refrigerant means that it is ____.
processed so that it meets the standard for new refrigerant
The principle of evacuating a system using a vacuum pump is to lower the system pressure so any moisture can ____.
boil off or vaporize
Air in a refrigeration system mainly causes ___?
the system to work harder due to increase in condensing temperature
*over time it can also degrade the oil and cause acids to form
The most accurate way to measure a vacuum is with a ____.
micron gauge
What is the micron level to which a system should be evacuated down to?
500
When charging refrigerant by weight you can charge with?
both liquid and vapor refrigerant
The sub-cooling charging method gives an indication of the amount of ____?
liquid refrigerant at the expansion device
What is the process called when each of the refrigerant used in a blended refrigerant leak at a different rate if released into the atmosphere changing the proportions of the refrigerants used in the blend?
fractionation
After a leak in a system using a zoetrope refrigerant is repaired and the system has been evacuated the system should be charged with ____?
new refrigerant
*its not possible to determine if the old refrigerant is the required blend
When charging a system that uses a zoetrope refrigerant the system should be charged with _____.
liquid refrigerant
When determining the type of burnout in a system with a hermetic compressor the fist thing to do is ____.
check the moisture and acid content of the system
NEMA states three phase motors should operate successfully under running conditions at rated load when the voltage imbalance does not exceed ____.
1%
A metering device is a refrigeration system control that ____.
converts high pressure high temperature liquid refrigerant to a low temperature low pressure mix of liquid and vapor refrigerant
A significant difference between a DX evaporator and a flooded evaporator is ____.
in the DX evaporator the refrigerant is converted to vapor in the evaporator whereas it remains in liquid form in the flooded evaporator
The correct location of a TXV sensing bulb is ____.
at the evaporator outlet
What is the purpose of a crankcase heater?
to prevent liquid refrigerant from slugging the compressor
What element in refrigerants causes ozone depletion?
chlorine
The component directly following the evaporator of a refrigeration system is the ____.
accumulator
When under a deep vacuum a hermetic refrigeration’s compressor ____.
motor winding could be damaged if energized
When evacuating a system, the use of a large vacuum pump could ____.
cause trapped water to freeze
The component of a refrigeration system which converts a high pressure vapor to a high pressure liquid is the ____.
condenser
Horizontal piping runs used in refrigeration systems should ____.
pitch down in the direction of refrigerant flow
A compressor with a piston that travels back and forth in a cylinder is a ____.
reciprocating
Components most often found in the refrigeration system liquid line are ____.
receiver, sight glass/moisture indicator, filter drier
Annealed copper tubing shall not be used in normal sizes larger than ____.
2”
The exhaust from a refrigeration equipment room shall not be less then ____ from a property line or opening into a building.
20 feet
Operating a three phase electrical motor at a phase imbalance above ____ will most likely damage the motor.
5%
The purpose of flux used in soldering is ____.
keeps the metal clean once soil has been removed
Why are expansion valves adjustable?
to adjust for different altitudes and to adjust for different sizes of liquid receivers
An ampere measures the flow of ____.
electrical current
When an air conditioning system is not in operation, the accumulator should have adequate liquid holding capacity of not less than ____ percent of the entire system capacity.
50
Open flame that comes in direct contact with R-22 creates ____.
phosgene gas
Effective July 1, 1992 section 608 of the ____ prohibits individuals from intentionally venting ozone-depleting substances used as refrigerants.
Refrigeration Recycling Rule
Section 608 does not consider small releases of refrigerant resulting from the disconnection of hoses, however, effective November 15, 1993 recovery and recycling equipment must be equipped with ____>
low-loss fittings
Technicians repairing small appliances such as household refrigerators, window air conditioners, or water coolers must recover ___% of the refrigerant when the compressor is not operational and ____% when the compressor is operational.
80/90
Refrigerant recovered or recycled can be returned to the same system or ____ without restriction.
systems owned by the same person
Refrigeration systems in commercial and industrial process refrigeration sectors are required to repair leaks within ____ days when the equipment leaks at a rate that would release ____ percent or more of the charge over a year.
30/35
Refrigeration systems in all sectors except commercial and industrial process refrigeration sectors are required to repair leaks that would release ____ percent or more of the charge over a year within 30 days of discovery.
15
To translate psig to psia when using a temperature-pressure chart, ____ must be added.
14.7
Refrigeration oil must be heated up to ____ degrees F before removing it from a system to minimize refrigerant release.
130
The EPA Type I Certification is for ____
servicing small appliances (household refrigerator, window air conditioners)
The EPA Type II Certification is for ____
servicing and disposing of high or very high pressure appliances except small appliances and MVAC’s
The EPA Type III Certification is for ____
servicing and disposing of low-pressure appliances
