HVAC II 29, 40 Quiz

Question 1

What is the first thing a technician should do before beginning troubleshooting?

Answer 1

Know the typical operating conditions of the system, and observe the entire system

Question 2

What is the coil to air temp relationship for a refrigeration system designed for minimum food dehydration?

Answer 2

8-12 degrees F

Question 3

What is the evap coil to air relationship when the compressor is not running?

Answer 3

The coil warms, increasing pressure on the low side of the system and eventually matches the box temp

Question 4

What is meant by the term “Approach” when dealing with evap chilling water?

Answer 4

Delta T between evap coil and cooling water leaving temp (Departure). Heat given to evap

Question 5

How does a TXV system respond to an overcharged refrigeration condition?

Answer 5

High head pressure and maybe high suction pressure, because superheat is down so valve will not fully open and will eventually close

Question 6

How does a capillary tube system respond to an overcharged refrigeration condition?

Answer 6

Higher head pressure. Will meter more refrigerant, because head pressure is higher, flooding the evap

Question 7

How does a TXV system respond to an undercharged refrigeration condition?

Answer 7

May hiss as a partial vapor/liquid mix goes through the valve. Valve will open fully, as superheat is constantly high

Question 8

How does a capillary tube system respond to an undercharged refrigeration condition?

Answer 8

Less refrigerant is metered through due to low head pressure

Question 9

What is the compressor’s job in an AC system?

Answer 9

To lower the evap boiling temp (through suction) to proper low level

Question 10

How is Head Pressure calculated?

Answer 10

Ambient temp + Condense temp above ambient (usu. 30) = Head Temp

Question 11

What is the gpm flowrate for waste water and cooling tower unit?

Answer 11

1.5gpm waste water, 3 gpm cooling tower

Question 12

What is the standard water temp increase across the condenser in cooling tower system?

Answer 12

10 degrees F

Question 13

What are six typical problems in an AC system?

Answer 13

1. Low refrig charge. 2. Overcharge. 3. Inefficient Evap. 4. Inefficient Condenser. 5. Restriction in refrig circuit. 6. Inefficient Compressor

Question 14

The standard design conditions for AC systems established by the ARI are outside temp____ degrees F, inside temp____ degrees F, with a humidity of____%.

Answer 14

95, 80, 50

Question 15

The typical temp relationship between a standard-efficiency air-cooled condenser and the ambient temp is.

Answer 15

30 degrees F

Question 16

The evap will normally operate at a ____ degree F boiling temp when operating at the 75 degree indoor temp with a 50% humidity condition.

Answer 16

40 degrees F

Question 17

A typical temp relationship between a high efficiency condenser and the ambient temp is:

Answer 17

20 degrees F

Question 18

How is the condenser high efficiency obtained?

Answer 18

Usually oversizing condenser, evap, and new alloys for heat exchangers

Question 19

What type of metering device is typical for high-efficiency systems?

Answer 19

TXV, sometimes fixed-bore

Question 20

What does the head pressure do if the suction pressure rises?

Answer 20

Increases

Question 21

What will cause the suction pressure to rise?

Answer 21

Higher indoor evap load, as from unit off for extended period

Question 22

The evap design temp may in some cases operate at a slightly higher or lower pressure and temp on high-efficiency equipment because the evap is larger.

Answer 22

Slightly higher. Absorbing more heat

Question 23

The seasonal energy efficiency ratio (SEER) includes the energy used in the ____ and ____ cycles.

Answer 23

Start up and shutdown

Question 24

The electrical operating conditions are measured with a ____ and ____

Answer 24

Voltmeter and Ammeter

Question 25

The three major power-consuming devices on an AC system that may have to be analyzed are:

Answer 25

Indoor fan motor, outdoor fan motor, and the compressor

Question 26

AC systems normally move about ____ cfm of air per ton.

Answer 26

400 cfm per ton

Question 27

The compressor amperage of a 3-ton system operating on 230VAC is approximately ___A.

Answer 27

17A

Question 28

Many ratings for components of an AC system are not completely accurate due to many different operating conditions that are called ___ ratings.

Answer 28

Nominal

Question 29

What occurs in the AC system is the outside temp increases?

Answer 29

Head pressure increases, and the capacity decreases