14

Question 1

Surrounding air temperature

Answer 1

Ambient temperature

Question 2

A control that has no connection to electrical power such as a TXV.

Answer 2

Mechanical controls

Question 3

Normally regulates other controls and does not carry much current (2A max).

Answer 3

Low voltage thermostat

Question 4

Detects presence of gas pressure in gas burning equipment before burners are allowed
to ignite.

Answer 4

Gas pressure switch

Question 5

Detects excess pressure in any system that contains fluid.

Answer 5

Pressure relief valve

Question 6

Bimetal formed into a shape like a cylindrical coil spring that provides longer travel when heated.

Answer 6

Helix coil

Question 7

High- and low-pressure controls built in one housing.

Answer 7

Dual pressure control

Question 8

Reduces gas transmission pressure to usable pressure at the burner.

Answer 8

Gas pressure regulator

Question 9

Safety device used on boilers to release excess pressure.

Answer 9

Boiler relief valve

Question 10

Keeps refrigerant from migrating to the oil during any long periods of off time.

Answer 10

Crankcase heat

Question 11

Contains a small amount of mercury that makes or breaks the electrical circuit contacts in a low voltage thermostat.

Answer 11

Mercury bulb

Question 12

Gas that will not support most chemical reactions, particularly oxidation.

Answer 12

Inert gas

Question 13

Uses a large diaphragm to sense very low air pressure in air ducts to sense blower air before heat is activated.

Answer 13

Air pressure control

Question 14

Thermistor or bimetal device that prevents motor from overheating.

Answer 14

Motor temperature cut-out

Question 15

Converts mechanical energy to operate an electrical function.

Answer 15

Electromechanical controls

Question 16

A central air conditioner is set to “Cool” but the system is not operating. You check the thermostat and see that the display is illuminated. You place the switch to the off position, wait a few minutes and then move the switch back to “Cool” and wait for the start delay to expire.
After 10 minutes, the unit still does not start. You pull the thermostat off the subbase to see if the wires are in the correct terminals. You observe that the red, green and yellow wires are in the correct terminals and the “C” terminal is not being used. The thermostat requires two AA batteries. The thermostat display is still illuminated.

You use your meter to check the batteries to see if they have the correct voltage. At what volt reading would you consider each battery to be no good?

Answer 16

Below 1.3 volts

Question 17

The batteries are above the minimum voltage reading so you don’t need to change them.
You can do one more test to confirm if the thermostat is the cause of the system not starting by doing what? Explain in detail.

Answer 17

Check for voltage in each of the wires and the transformer

Question 18

Immediately after you do the test above in question 17, you hear and feel the blower operating but when you go outside to check the compressor, only the condenser fan is operating and the compressor isn’t running. What is wrong?

Answer 18

Possible bad start components, bad compressor, internal overload tripped.

Question 19

The high event on a thermostat or pressure control is also known as the cut-in point. T/F

Answer 19

T

Question 20

Oil pump discharge pressure is 200 psig and the suction pressure is 120 psig. Net oil pressure is 320 psig. T/F

Answer 20

F

Question 21

Non-condensables in a system will cause higher head pressure because it takes up
valuable volume in the condenser. T/F

Answer 21

T

Question 22

A water regulating valve for a water-cooled condenser is a mechanical control. T/F

Answer 22

T

Question 23

The pressure setting on a relief valve can be adjusted. T/F

Answer 23

F

Question 24

Oxidized mercury in a bulb switch could cause the switch to always be in the
closed position. T/F

Answer 24

T

Question 25

A broken condenser fan motor will cause a low-pressure control to shut the compressor off. T/F

Answer 25

F

Question 26

Do not use water to cool a compressor housing made of cast iron. T/F

Answer 26

T

Question 27

Brass or copper mounting straps should be used to secure sensing bulbs to the suction line where freezing temperatures occur. T/F

Answer 27

T

Question 28

The thermometer indicates the temperature of the bulb at the end of the thermometer, not the temperature of the substance it is in contact with. T/F

Answer 28

T

Question 29

To adjust the heat anticipator in a non-digital/electronic thermostat, measure the current between the R and Y terminals with a clamp meter when the heat circuit is energized. T/F

Answer 29

F

Question 30

The cold anticipator shuts the compressor off a few degrees before the set point temperature to allow for residual cooling to prevent overshoot. T/F

Answer 30

F

Question 31

What is used in a non-digital/electronic thermostat to reduce system lag and how is it installed in the circuit of the thermostat?

Answer 31

A cold anticipator, in a parallel circuit.

Question 32

If the internal overload on a compressor has functioned, how do you verify it with your meter and what would your meter readings be?

Answer 32

Check C-R R-S C-S OL

Question 33

A thermostat has a cut-in setting of 40°F and a cut-out setting of 35°F. The differential is set at 5°. What is the cut-out temperature if the differential remains the same, but the cut-in temp is increased to 45°F?

Answer 33

10°F

Question 34

How long is the time delay in an oil pressure monitoring control to allow oil pressure to build up when a compressor first starts?

Answer 34

90 seconds

Question 35

What is the best procedure to handle a hot compressor and you suspect the internal overload has functioned?

Answer 35

Turn it off let it cool and see if it resets.