In Figure 39-34, what happens when the defrost relay DR is ...

[fox]

In Figure 39-34, what happens when the defrost relay DR is energized?
 
  What will be an ideal response?

Question 2

Explain a method used to determine if noncondensables are in a refrigeration system.
 
  What will be an ideal response?

[duke02]

Answer to Question 1

DR NO contacts energize the RVS to put the unit into cooling mode. Another DR NO contact energizes the HS1 coil to bring on the strip heat. The DR NC contacts break the circuit to the outdoor fan motor, turning it off.

Answer to Question 2

The method used is as follows:
Determine the type of refrigerant in the system.
Electrically disable the compressor and allow the condenser fan to operate. Attach a temperature probe to both the discharge line and liquid line. Place a third temperature probe to measure the temperature of the air entering the condenser.
Connect a pressure gauge on the system to measure the pressure of the refrigerant in the condenser.
When all three temperature probes

[fox]

Thank you!

[duke02]

Always glad to help...