Refrigeration Flashcards
Understanding Refrigeration
Which section of piping is “A” in the image below reffered to as?
Discharge line
Which section of piping is “B” in the image below reffered to as?
Liquid line
Which section of piping is “C” in the image below referred to as?
Suction line
What state is the refrigerant in the condensor coil?
Saturated
What state is the refrigerant in the evaporator coil?
Saturated
What state ideally is the refrigerant at “A” in the image below?
Vapour
What state ideally is the refrigerant at “B” in the image below?
Liquid
What state ideally is the refrigerant at “C” in the image below?
Vapour
What is the maximum temperature drop you can have across a filter drier?
3°f
What is the purpose of an accumulator?
To prevent liquid refrigerant from entering the compressor.
What is the ideal amount of superheat in a system?
10°f of superheat
What is the ideal amount of subcooling in a system?
10°f of subcooling
What is the ideal SST (Saturated suction temperature)
35°f - 45°f
How do you calculate subcooling?
SCT - Liquid line temperature
For example
SCT - 95°f
Liquid line temperature - 85°f
Subcooling: 95 - 85 = 10
How do you calculate superheat?
Suction line temp - SST
For example
SST - 40°f
Suction line temperature - 55°f
Superheat: 55 - 40 = 15
Saturated means …
**the boiling point, of a vapour/liquid mixture **
The slower the fan speed the —– the temp drop but the —– you will boil the refrigerant.
higher/lower
more/less
higher the temp drop but the less you will boil the refrigerant
How do we know we have %100 liquid going to the TXV
By having 10°f of subcooling
What is wrong with the system pictured?
Fan speed to high.
What is wrong with the system pictured?
Fan speed to low.
What is wrong with the system pictured?
Nothing.
What is wrong with the system pictured?
It is low on charge
What is wrong with the system pictured?
There is no load.
What is wrong with the system pictured?
The system is overcharged.
What is wrong with the system pictured?
Fan speed to high.
What is wrong with the system pictured?
Airflow is low.
What is wrong with the system pictured?
High load on the system.
What is wrong with the system pictured?
Low charge.
What is wrong with the system pictured?
Bad Metering Device.
What is wrong with the system pictured?
Overcharged.
What is wrong with the system pictured?
Restriction.
What is wrong with the system pictured?
Metering device is stuck because refrigerant was added and SST didnt change.
What is wrong with the system pictured?
Fan speed set to high.
What is wrong with the system pictured?
Fan speed set to low.
What is wrong with the system pictured?
High load.
What is wrong with the system pictured?
Overcharged.
What is wrong with the system pictured?
Restriction
What is wrong with the system pictured?
Empty.
You add refrigerant to this system but your SST does not move. What is your next step?
Pump down test to see if the TX valve isn’t working.
What is wrong with the system? What do you need to do?
You arrive to find the coil is frozen over. You check history and you find that the evap and blower/hx were cleaned 12 months ago. Filter is clean, all registers are open, including return. The ECM is speeding up to attempt to move correct CFM through the frozen coil, you ensure it is set to 400 CFM per ton.
Either the customer changed the filter before you got there or the ECM motor has 1 speed getting stuck.
In a residential A/C, the optimal range for saturated suction temperature is 30°F-40°F when considering due point.
True/False
False
Optimal SST is 35°F - 45°F
What is the name of the gas created when refrigerant is burned?
phosgene gas
What are the 4 types of metering devices in residential AC?
1. Piston
2. Thermostatic expansion valve
3. Electronic expansion valve
4. Capillary
How do you charge a system with a piston metering device?
Superheat
How do you charge a system with a TXV metering device?
Subcooling
How do you charge a system with an EEV metering device?
Weighing it in or by subcooling on the max speed
How do you charge a system with a capillary as a metering device?
Superheat
What is the function of a TXV?
Maintains a fully saturated evaporator coil without damaging the compressor?
During the winter what is the purpose of the condenser fan motor in a heat pump?
To maintain pressures and temperatures across the heat exchanger
If a compressor is recieving high super heat the system can become compromised and run the risk of creating what?
Toxic acidic refrigerant & oil
Which one of the following might you see in a system if there is no TXV?
Check - Flow piston
Back - Check piston
Slam - Check piston
Check - flow piston
How much quieter is a side discharge heat pump vs a traditional heat pump?
36% quieter
An air restriction will cause the following readings: Normal subcooling normal head pressure - low superheat low pressure
True/False
True
3 tonnes of refrigeration is equal to?
A. 200 BTU/min
B. 400 BTU/min
C. 600 BTU/min
D. 800 BTU/min
C. 600 BTU/Min
With regards to a TX valve, if the sensing bulb loses its charge, the valve will be?
A. There is no sensing bulb on a TX
B. Open
C. Closed
D. Mid position
C. Closed
An externally equalized TX valve senses evaporator ___?
A. Outlet Pressure
B. Inlet Pressure
C. Head Pressure
D. Saturation Temperature
A Outlet Pressure
