UNIT 4 Flashcards
(54 cards)
MATCH THE TYPE OF EXTINGUISHER WITH THE TYPE OF MATERIAL IT IS DESIGNED TO EXTINGUISH.
Fires in combustible metals, titanium, zirconium, sodium, lithium, and potassium
Class D fires
Fires and flammable liquids, combustible liquids, petroleum, greases, tars oils, oil, based paints solvents, lacquers, alcohols, and flammable gases
Class B fires
Fires that involve energized electrical equipment
Class C fires
Fires in ordinary combustible materials, such as wood cloth, paper, rubber, and many plastics
Class A fires
Fires and cooking appliances that involve combustible cooking media (vegetable or animal oil and fats)
Class K fires
An R-22 cylinder is in a truck with a temperature of 120°F. What would the pressure be in the cylinder?
259.9 PSIG
The cylinder of R-22 above in #6 has an internal surface area of 1500 in.². What is the total outward force of the refrigerant against the inner wall of the cylinder in tons of pressure?
1500 in.² times 259.9 PSIG= 389,850/2000= 194.925 Tons
When it is necessary to perform electrical work in an area that has a damp or wet floor, what safety precautions can be taken to minimize the chance of electrical shock?
- Use only the proper piece of test instrumentation, and make certain that they are in good working condition.
- Where heavy shoes with insulating sole heel.
In what circumstance would an individual get frostbite when working in the refrigeration trade?
-if a person is careless, and the refrigerant gets on a persons, skin or eyes, it will cause frostbite.
How are refrigerant cylinders oriented when in storage or transporting?
-refrigerant cylinders should be stored and transported in the upright position to keep the pressure relief valve in contact with the vapor space.
What precautions must you take if you suspect a compressor has experienced a burnout?
Make sure there is emergency eye and body wash stations readily available due to potential acid in the compressor.
The safety classification for refrigerant is B3. What does that mean?
Highly flammable and toxic
It is 20 feet to the top of the building parapet. What is the minimum length of the extension ladder used and how far from the base of the building should the ladder be positioned?
5 feet from building and 24 feet minimum length. Extension ladders should extend at least 3 feet above the landing surface.
Horizontal distance should be 1/4 the working length of the ladder which would be 5 feet or 5.25 feet using Pythagorean theorem.
What are the symptoms of heat exhaustion?
- Feeling faint or dizzy
- Excessive sweating
- skin is cool, pale and clammy
Current flow of……..A or less through the body can be fatal
0.015A
Customer says that every time the air conditioner is turned on, the 3A fuse in the low-voltage control circuit pops. You suspect the contactor in the outdoor unit is the problem, So you disconnect power to the outdoor unit and disconnect the low-voltage wires attached to the contactor. you set your meter to resistance and check the contactor coil. your meter reads 0.8 ohms. How many amp is the contactor drawing when the contactor is energized with 27 V?
E= I x R————27V= I x 0.8———-I= V/R——I= 27v/0.8ohms= 33.75 amps———-
You have a spare contactor in your truck to replace the bad contactor in number 16 above. before you replace the bad contactor, you check the resistance in the new contactor coil to make sure it will not draw more than 3A or the fuse in the low voltage circuit will blow. What should the resistance of the new contactor coil measure so that the 3A fuse will not blow when the circuit is energized?
I= V/R—-to find resistance, rearrange formula——R= V/I
R= 27/3= 9 ohms (maximum)
Occurs when a person becomes part of the circuit. Can affect the heart and stop it from pumping.
Electric shock
Freezing of body temperature
Frostbite
Moving refrigerant into or out of a refrigeration system via a manifold, gauge recovery machine or vacuum pump
Transferring, refrigerant
Safety device on a pressure vessel or system that are under pressure prevents equipment, damage or rupture of pressure vessels
Relief valve
Fans, Motos or equipment using belts, drives, shafts, or chains that rotate. May cause injury or death if a person interferes with normal operation.
Rotating equipment
Used to move heavy objects. Usually a flatboard with wheels that can move in any direction.
Portable dolly
A refrigeration system consisting of a compressor, evaporator condenser and metering device configured into one casing, much like a window, air conditioning unit, but capable of providing great cooling capacity
Package refrigerant equipment
