Hvac Round 1 Flashcards
Learn about hvac
How do you find the TOTAL superheat?
Suction line - saturated temp = Total superheat
Where is the liquid line located?
It is located on the high side and runs from the condenser coil to the metering device
What are three ways to transfer heat?
- Conduction
- Convection
- Radiant heat
What is the suction line?
Tubing that carries refrigerant vapor from evaporator coil to compressor.
Ex. The cold tube with the covering and it’s bigger
Where is the discharge line?
It is between the compressor and condenser
Ex. The skinny line
What is a metering device purpose?
Converts high pressure liquid into a low pressure liquid by drastically reducing the temperature
What does the evaporating coil do?
This coil absorbs heat
As the air from the blower fan moves over the coil. The cold refrigerant inside the coil removes heat from the homes air
What is the saturated temperature?
Saturated temperature means boiling point.
Located on your Guage
How long should you let the system run before charging up the system?
15min
How do you find the TARGET superheat?
- You need a good wetbulb reading near the biggest return
- You need a dry bulb reading near the bottom of outdoor unit in th shade
Then you enter both reading into the app
If you have a TXV in front of the evaporator coil what method do you use to charge the system?
SUB COOLING METHOD
Before you start charging a system the saturated temp on both ends should be what degree?
32 degrees
How do you get the wetbulb reading?
You get the wetbulb by taking a psychrometer and taking the reading at the biggest return vent
Purpose of a filter drier?
Collects moisture, dirt, metal, and other debris to prevent any from entering the metering device.
What is superheat?
And where does it occur?
Superheat is when the vapor is heated above it’s boiling point
And it occurs in the evaporator to protect the compressor
What is subcooloing?
And where does it occur?
Subcooloing happens when a liquid is cooled below it’s normal boiling point
And it occurs in the condenser to protect the expansion device
What is a pressure switch?
A protective device that usually always sits open.
The only time a pressure switch closes is when the induced fan is running. It creates a vacuum and closes
What is a Accumulator?
A tank in the suction line that prevents liquid refrigerant from flowing through the suction line and into the compressor.
What are the three main components of a furnace in order and how much voltage does each take?
- Induced fan motor connected to the pressure switch 120v (line voltage)
- Hot Surface igniter 120v (line voltage)
- Gas valve 24V (low voltage)
What is the purpose of a transformer?
Main purpose is to convert line voltage
Ex 120v to 24v
What is the normal atmosphere pressure?
14.7
If your system has a piston, fixed office or capillary tube before the evaporator coil, what method should you use for charging up the system?
Superheat method
Where is the evaporating and condenser coil located?
- Evaporating coil is in the house
2. Condenser coil located outside the house.
What is a line set?
Line sets is simply a pair of copper tubes that connects a condenser to an evaporator
The main difference between a split system and package unit
What is the purpose of a thermostat?
What do the wires mean?
The thermostat is the main control of the action unit and runs off 24V
Red wire - power
Green wire- fan
White wire- heat
What is the purpose of a HEAT PUMP indoor coil and where is it located?
It warms or cools the air for the conditioned space.
Heat pumps evaporator coil is located at the bottom or middle of furnace
What does refrigerant do?
Acts like a sponge that is used to soak up and move heat
What is a compound Guage?
It’s the blue side Guage and can read below and above atmospheric pressure
What is flash gas?
Instantaneous evaporation of some liquid refrigerant
What does LOTO mean?
It means lockout or tag out. And it is a safety procedure to make sure dangerous machines are properly shut off and not be able to start up again
When using the superheat method to charge up a system, what Guage do you use when charging it checking?
Low side or blue guage
What does EPA stand for?
ENVIRONMENTAL PROTECTION AGENCY
When would you use DC and AC voltage?
- Battery power works off DC voltage
2. inside buildings you come across AC voltage
How does heat travel?
From hot to cold
4 Major parts of refrigeration
- Compressor
- Condensor coil
- metering device
- evaporator coil
What is refrigeration?
To remove heat from a space where it is not wanted
What is dry bulb?
It’s just ambient temperature
What is the compressor?
The main part of the unit and is the only electric component.
Only gas can travel through a compressor.
It raises the pressure and heat of the vapor as it pumps into the high side
What does OSHA stand for?
Occupational Safety and health administration
When does water begin to boil and freeze?
212 boil
32 freeze
If the superheat is lower than targeted superheat do you add or recover refrigerant?
The system is overcharged and you need to recover refrigerant
If the supergeat is HIGHER than targeted superheat do you add or recover refrigerant?
Add refrigerant
What is a heat pump system?
A compression refrigeration system that can reverse the circulating flow of refrigerant in order to add heat or remove heat from a conditioned space.
This is a possible because it has a reversing valve
How do you find TOTAL subcooling?
Saturated temp - discharge line = Subcooling
What is a high limit switch?
Is a protective part of a furnace. If the temperature gets to high it will open the circuit cutting off the gas valve.
Check for continuity to see if functioning right.
What does a HEAT PUMP outdoor coil do?
The refrigerant cool that absorbs or expels heat for the indoor coil
Remember that your target superheat is a MOVING number so often should you check?
Check every 5-8 mins
In a heat pump system, Cooling mode usually means it runs how?
Cooling mode: runs like traditional SPLIT SYSTEM on a hot day
In a heat pump, when it’s in heating mode, how does it run?
Heating mode: the outdoor unit acts like evaporator coil and inside coil acts as condenser
This is possible because of the reversing valve.
On a heat pump system the absorption and rejection areas switch depending on what?
The directional flow of refrigerant
What is a solenoid valve?
An electro magnetic valve that is employed to control the flow of liquid or gas
