General Flashcards
What is the purpose of a head pressure control valve?
To maintain a minimum head pressure in low ambient conditions.
How does a reverse acting high pressure switch close?
On a rise in pressure.
Why is head pressure control important?
If the head pressure is too low, the pressure drops across the metering device are increased.
What is the closing action of an ORI valve?
Open on rise of inlet, or close on fall.
How does an ORD valve operate?
It opens on a rise of differential, and bypasses the condenser to raise the pressure in the evaporator.
Which is known as a combination valve?
The OROA valve, which opens on a rise of outlet.
What is the opening operation of a EPR valve? (Evaporator Pressure Regulator)
It is an ORI valve, or open on rise of inlet.
What does a CPR valve do?
Protects the compressor from over-loading.
Is a hot gas by pass valve designed for hot gas defrost, or capacity control?
It is used for capacity control.
What type of valve is a hot gas by pass?
A hot gas by pass valve is a CRO valve.
What is the purpose of the solenoid valve used with the hot gas by pass valve?
The solenoid is used to isolate the valve, so the system can pump itself down.
What’s required if the hot gas by pass valve is piped into the suction line adding extra super-heat?
A de-superheating TXV is required.
What does a DDR valve do?
It maintains the differential at the outlet.
What is the purpose of an accumulator?
To stop liquid from flooding back to the compressor.
A fusible plug is limited to what?
Three cubic feet of internal volume.
A type C txv is good for what temp range?
50F to -10F
What isn’t a symptom of an undercharged cap tube?
Increased sub-cooling.
A TXV with a gas charged bulb?
Limits maximum suction pressure.
Purpose of a DDR valve?
Lower the liquid pressure below the discharge pressure while in defrost mode.
What is the purpose of a hot gas bypass?
Prevent the suction pressure from falling below system design pressure in a low-load situation.
A 3 way diverting solenoid valve has…?
One inlet, and 2 outlets but only uses one outlet at a time.
Best desiccant for removing moisture from a system?
Molecular sieve.
Suction line accumulators are designed to hold?
50% of the charge.
Refrigeration mechanics typically use what type of copper?
Type L, outside diameter.
