Why are systems with fixed restriction metering devices critical ...

[B]

Why are systems with fixed restriction metering devices critical to charge?
 
  What will be an ideal response?

Question 2

What is the purpose of an oil return system for a chiller?
 
  What will be an ideal response?

Question 3

Why must refrigerants that fractionate, such as R-410a, be charged as a liquid?
 
  What will be an ideal response?

[jamesnevil303]

Answer to Question 1

They cannot adjust to changing conditions and they have no liquid receiver to store extra refrigerant.

Answer to Question 2

The oil in many large commercial centrifugal and screw type chillers travels through the system and collects in the bottom of the cooler. Without some type of oil return system, the oil will not be able to be reintroduced into the lubrication circuit.

Answer to Question 3

Refrigerants that fractionate, such as R-410A, must be charged as liquid to prevent the separation of the refrigerant.

[B]

Wow, this really help

[mammy1697]

Thanks for the timely response, appreciate it