RSES Expansion Devices 3

Question 1

A float valve in a flooded evaporator system responds to changes in:

Accepted Answer

Refrigerant liquid level

Answer

The float valve maintains a constant liquid refrigerant level in the flooded evaporator by opening and closing based on liquid level.

Question 2

What is the primary advantage of an electronic expansion valve (EEV) over a TXV?

Accepted Answer

More precise refrigerant flow control across varying conditions

Answer

EEVs use electronic controls and stepper motors for precise modulation, outperforming TXVs in variable-load or multi-evaporator applications.

Question 3

The TXV sensing bulb must be mounted in proper thermal contact with the suction line because:

Accepted Answer

It must accurately sense refrigerant temperature to control superheat

Answer

The sensing bulb contains a refrigerant charge that expands or contracts based on suction line temperature, which opens or closes the TXV.

Question 4

Which of the following would cause a TXV to hunt (cycle open and closed rapidly)?

Accepted Answer

Oversized TXV for the system load

Answer

An oversized TXV over-responds to load changes, causing hunting as it continually opens too far then closes too far.

Question 5

In a refrigeration system using a capillary tube, what happens during the off cycle?

Accepted Answer

Pressures equalize between high side and low side

Answer

A capillary tube has no check valve function, so pressures equalize during the off cycle, making startup easier for the compressor.

(RSES) Refrigeration Service Engineers Society Certification Practice Test