Lesson 3 Review

Question 0

SEER is the measure of a heat pumps____. It is expressed in___

Answer 0

Cooling efficiency; Btu/Watt

Question 1

What is Refrigeration?

Answer 1

The process of transferring heat energy from the area it is not wanted to an area it won’t make a difference.

Question 2

The typical compression ratio for a heat pump operating in cooling mode is approximately?

Answer 2

3:1

Question 3

What is the coefficient of performance (COP) of a heat pump?

Answer 3

How much heat the heat pump is producing compared to and electric furnace using the same amount of electricity.

Question 4

A heat pump thermostat is set so that there will be a deadband range of about ___ deg. F between the heating & cooling cycles, A closer setting might result in ___

Answer 4

2 to 4 degrees F ; frequent cycling

Question 5

A typical reversing valve cylinder with 3 tubes on one side and a single tube on the other side. The center tube of the three is always the compressor ___ connection. The single tube on the opposite side of the cylinder is always the compressor ___ connection.

Answer 5

suction, discharge

Question 6

At what liquid line temperature does a temperature-activated defrost control typically terminate the defrost cycle?

Answer 6

50 to 65 deg. F

Question 7

At what head pressure does a pressure-activated defrost control typically terminate the defrost cycle?

Answer 7

250 to 300 psig

Question 8

Why does a heat pump require three-function control?

Answer 8

because a H.P. provides 3 functions: heating, cooling and defrosting the outdoor coil of ice build up

Question 9

What is meant by excessive supplemental heat?

Answer 9

More heat than would be required to neutralize the cooling effect that occurs during the defrost cycle

Question 10

What is the “critical point” of refrigerant?

Answer 10

The maximum saturation condition at which evaporation and condensation may occur

Question 11

The physical properties of a refrigerant may be represented as a curve on a pressure-enthalpy diagram. Plots points that fall outside and to the right of curve indicate that refrigerant is a ___. Plot points that fall outside and to the left indicate that the refrigerant is an ___. Plot points that fall inside the curve itself indicate that the refrigerant is a ___.

Answer 11

Superheated vapor, subcooled liquid, mixture of saturated liquid and vapor

Question 12

One of the most important principles of refrigeration is that an increase in pressure on a liquid results in an ___ in the liquids boiling temperature.

Answer 12

Increase

Question 13

In the cooling mode, which coil (indoor or outdoor) of a heat pump system functions as a condenser? Which coil during the heating mode?

Answer 13

In the cooling mode, the outdoor coil functions as the condenser. In the heating mode, the indoor coil functions as the condenser.

Question 14

What is meant by referring to a vapor compression system as a “closed” system?

Answer 14

The term “closed” means the system continually repeats itself without depleting the refrigerant contained within it.

Question 15

Why are suction-line accumulators and crankcase heaters often required to protect heat pump compressors?

Answer 15

liquid refrigerant can build up in the crankcase during the off-cycle which causes poor lubrication on start up and increases bearing wear.

Question 16

Why is the indoor air volume required for heat pump operation greater than the volume required for cooling only applications?

Answer 16

To ensure adequate condensing of the refrigerant during the heating mode.

Question 17

Why does the indoor coil of a heat pump need more area than the indoor coil of a cooling only unit?

Answer 17

To prevent the condensing temperatures and corresponding head pressures from becoming to high during the heating cycle