Hvac Fundamentals Flashcards
What is a reamer blade used for?
A. Cutting tubing
B. Cutting sheet metal
C. Removing burrs from inside of tubing
D. Removing sweat type filter driers
C. Removing burrs from inside of tubing D
If the pressure exerted upon a liquid is reduced, what effect does this have on the liquids boiling point temperature?
A. It raises the boiling point
B. It lowers the boiling point
C. It has no effect on the boiling point
D.it either raises or lowers the boiling point, dependent on the liquid
B. It lowers the boiling point C
An exposed central support that runs parallel to the ceiling is called a
A. Beam
B. Joist
C. Stud
D. Plate
A. Beam
What should always be worn when brazing?
A. A respirator
B. Earplugs
C. Tinted safety glasses or goggles
D. A personal alarm
C. Tinted safety glasses or goggles D
Why would earmuffs or plugs be important in this field ?
For when you are fabricating sheet metal or working with small machines
When using any electrical tool with a cord, you should always connect that tool to what?
GfCI or wall plug.
There are two type of hazards that you can encounter when brazing and soldering, what are those two things?
- The heat coming off the materials you are using
- The other involves the fumes from the gases used in each process
When brazing what two safety equipment items should you be using and what for?
- Gloves to protect your hands from the heat
2.Safety goggles to protect your eyes from the brightness of the torch
What are the three things you should never let oxygen come in contact with?
1.oil
2.grease
3. Flammable substances
At what psi does Acetylene become unstable?
Anything over 15psi
True or False you can get Acetylene tanks filled up anywhere
False. Only authorized gas distributors should refill them
What are the two acceptable purging gases used in the field?
1.Nitrogen
2.carbon Dioxide
What psi should you set your regulator on your nitrogen bottle when brazing?
You should set your regulator to 1 or 2 psi
Why should you let nitrogen flow through the lines when you braze?
To minimize the oxidation inside the piping
Nitrogen is not hazardous
True or False
False. Nitrogen is an inert gas, it can displace oxygen and result in oxygen deprivation
Is nitrogen heavier or lighter than air?
It is lighter
What type of fire extinguisher do you need in your truck and why?
You need a class b fire extinguisher made for chemical fires
Before you work with any gases involved in brazing and soldering what should you read first?
The SDS or SAFETY DATA SHEET
What is the maximum temperature you can keep a refrigerants cylinder in an area?
125F
Girders and trusses are used for what in construction?
Support
What is a Girder?
It’s a main component in a framed floor and support the joist that hold the flooring boards
What is a TRUSS?
It’s a combination of structures creating a framework to connect load bearing walls
What would a beam be used for in construction?
It’s generally engineered to carry structural loads over long open spans
What is a JOISTS in construction?
Are small rectangular sections of wood that rest on wall framing and support the ceilings and floors
What three things must be present for combustion to happen?
1.Fuel
2.oxygen
3.heat
What is Pascal’s law?
States that gas exerts equal pressure in all directions in a closed container
What is Charles law?
States that the volume of a gas is directly proportional to the absolute temperature.
What is the equation for Charles law?
Vi/vf = Ti/Tf
What does Vi and Vf stand for?
Initial and final volume
What does Ti and Tf stand for?
Initial and final temperature
What is Boyle’s Law?
States that an increase in pressure on a gas causes a decrease in its volume
What is the Gay-Lussac’s Law?
States the pressure of a gas is directly proportional to it’s temperature
What is subcooling?
The temperature of the liquid refrigerant leaving the condenser of a ac unit
What is superheat?
The temperature of vapor refrigerant leaving the evaporator of an ac unit
What’s the difference between class 1 wiring and class 2 wiring?
Class 1 wiring is used for thermostats, with a maximum of 30 volts
Class 2 circuit provides power to the equipment with acceptable protection from electrical shock
What does AHRI stand for and what it means?
The air conditioning, heating and refrigeration institute
And it develops standards and guidelines meant to improve product performance
Propane and Butane are (BLANK) than air
Heavier
Gas valves operating in furnaces, boilers, and larger appliances have a typical voltage rating of what?
24v
Sight glass is present at the (BLANK) in the refrigeration cycle
Liquid line
What is used to remove the trapped air from a low pressure system from the top of the condenser?
Purge unit
What is used to remove the trapped air from a low pressure system from the top of the condenser?
Purge unit
Which of the following law states that the total pressure of a confined mixture of gases is the sum of pressures of each of the gases in the mixture
Daltons Law
The Curved boundary In Psychrometric chart indicates what?
Saturation
1 horsepower = how many watts?
746
reclaimed refrigerant must meet the standards of (BLANK)
before it can be resold:
ARI 700
In a Psychrometric chart, dew point temperature lines are represented as:
Lines parallel to x axis
What is a Fuse used for?
It prevents short circuits
Which compressor operates most efficiently with high molecular weight, and high specific volume refrigerant?
Centrifugal compressor
Based on average conditions what percentage is the refrigerant holding capacity of an accumulator ?
65%
The horsepower required for any fan or blower varies directly as the (Blank) of the speed?
CUBE
What is diminished by the fan’s velocity pressure?
Static pressure
The higher the suction pressure the greater efficiency of the what?
Compressor
Which compressor has pulsations?
Reciprocal Compressors
An amperage is a measurement of what?
Electric current
Locked Rotor Ampere (LRA) current of a motor will be typically how many times more the normal running current of a motor
5 to 7 times
As the moisture present in the air increases, the wet bulb depression does what?
Decreases
The wet bulb depression is the difference between the dry bulb temperature and the wet bulb tem-perature.
What is the cubic feet of the mixture per pound of dry air?
Specific volume
Variable Speed Drive (VSD) systems used in HVAC applications works by converting the AC main supply to DC using what?
Rectifier
The (BLANK) is made of two different metals that
expand at different rates when heated and is used as a switch that turns on/off the air conditioning sys-tem.
Bimetallic strip
A motor contactor main purpose is to what?
Turn the motor on and off
Low pressure steam boilers will have operating pressure less than what psi?
15psi
Low-pressure steam boilers are typically used in residential and commercial applications where the need for high-pressure steam is not required.
According to ASME, the safety valve of the boiler should be tested every how many days ?
30 or a month
For every 1000 feet above sea level, the capacity of a natural gas furnace is de-rated by what percentage?
4%
This is because the air is less dense at higher altitudes, which means that there is less oxygen available for combustion. As a result, the furnace has to work harder to produce the same amount of heat, which can lead to decreased efficiency and increased wear and tear on the unit.
Dew point temperature is the temperature at which web bulb temperature is (BLANK) to dry bulb temperature
Equal too
Which of the following is not correct with respect to water tube boilers:
Higher steam output
Smaller size
Operate at lower pressures
Longer life span
Operate at lower pressures Longer
What is used to measure the pressure drop across the air filters:
Manometer
(BLANK) is the temperature which moisture condenses out the air
Dew point temperature
An oil separator is located in the (BLANK) of the refrigeration cycle.
Discharge line
What is an oil separator?
device that removes oil from the refrigerant as it flows from the compressor to the condenser.
What compressor uses two special helical rotors that introduce suction vapors and compress them?
Scroll compressor
What is used to control the flow of refrigerant in an air conditioning or refrigeration system?
Expansion valve
The presence of refrigerant vapor upstream of the (BLANK) is very undesirable
Expansion valve
Oxygen will explode when it comes into contact with compressor oil in refrigeration system
True or false
TRUE
