Thermostats

Question 1

A thermostat that remembers set points and adapts system operation and cycles accordingly is a _____ thermostat.

Answer 1

learning

Question 2

The type of HVAC system operation that regulates the increase or decrease of intensity and can result in significant energy usage reduction over time is ____ operation.

Answer 2

modulating

Question 3

The longer a bimetal coil is, the ____.

Answer 3

longer it will stretch

Question 4

A switch used with a bimetal coil that consists of a pair of contacts in a glass tube that changes position based on magnets is a ____ switch.

Answer 4

reed

Question 5

A switch used with a bimetal coil that consists of a glass tube containing wire contacts and a puddle of liquid that changes position based on its physical position is a ____ switch.

Answer 5

mercury

Question 6

The difference between a heating-only thermostat with two wires and heating-only thermostat with three wires is the addition of a ____.

Answer 6

holding circuit

Question 7

Temperature swing is the total difference between ____.

Answer 7

high and low temperatures in a room

Question 8

For a heating thermostat, system lag occurs when temperature ____.

Answer 8

drops below the cut-in value

Question 9

A heat anticipator’s purpose is to switch ____.

Answer 9

off the heating system just before reaching the cut-out temperature

Question 10

Anticipators are basically small —-.

Answer 10

resistors

Question 11

A cooling anticipator’s purpose is to switch ____.

Answer 11

on the cooling system just before reaching the cut-in temperature

Question 12

A cooling anticipator is always installed in ____.

Answer 12

parallel with the thermostat switch

Question 13

The number of wires to connect to a combination thermostat depends primarily on ____.

Answer 13

thermostat features and stages of operation

Question 14

the primary purpose of a multistage thermostat is that it can control an HVAC system’s ____.

Answer 14

capacity

Question 15

To control higher-current loads, a low-voltage thermostat will usually use ____.

Answer 15

relays and contactors

Question 16

The VA rating of a step-down transformer used with thermostats is used to determine _____.

Answer 16

secondary side current rating

Question 17

Low-voltage thermostats wiring for lengths up to 50’ should normally be at least ____.

Answer 17

18 AWG

Question 18

Low-voltage thermostats wiring for lengths over 50’ should normally be at least ____.

Answer 18

16 AWG

Question 19

Millivolt thermostats can only be used in certain ____ systems.

Answer 19

heating

Question 20

The sensing element used in millivolt thermostats in a(n) ____.

Answer 20

thermocouple

Question 21

To operate, a millivolt thermostat depends on a(n) ____.

Answer 21

standing pilot light

Question 22

The electrical load that a millivolt thermostat is used to actuate is a ____.

Answer 22

solenoid

Question 23

A thermostat that draws a small amount of power from the low-voltage side of the HVAC system control to operate its electronics is a ____ thermostat.

Answer 23

power-stealing

Question 24

Common connection terminal on a thermostat.

Answer 24

C

Question 25

Compressor contactor (stage 2) terminal on a thermostat.

Answer 25

Y2

Question 26

Condensing unit (compressor) contactor terminal on a thermostat.

Answer 26

Y

Question 27

Cooling power terminal on a thermostat.

Answer 27

Rc

Question 28

Damper terminal on a thermostat.

Answer 28

M1 or DMP

Question 29

Dehumidifier terminal on a thermostat.

Answer 29

DHD

Question 30

Fan relay (cooling only) terminal on a thermostat.

Answer 30

G

Question 31

Heating power terminal on a thermostat.

Answer 31

Rh

Question 32

Heat pump auxiliary heat terminal on a thermostat.

Answer 32

Aux/E

Question 33

Heat relay (stage 1) terminal on a thermostat.

Answer 33

W

Question 34

Heat relay (Stage 2) terminal on a thermostat.

Answer 34

W2

Question 35

Humidifier terminal on a thermostat.

Answer 35

HMD

Question 36

Indoor temperature sensor terminal on a thermostat.

Answer 36

In or IDT

Question 37

Reversing valve terminal on a thermostat.

Answer 37

O/B

Question 38

HVAC system settings are often set and managed using ____ on a circuit board or thermostat subbase.

Answer 38

DIP switches

Question 39

Free cooling is a method of cooling a building using a(n) ____.

Answer 39

air-side economizer

Question 40

For best results, free cooling should be used on a thermostat that has ____.

Answer 40

``` enthalpy control (outdoor air sensor) ```

Question 41

When free cooling is used on a forced-air system with mechanical air conditioning, a ____ thermostat must be used.

Answer 41

multistage

Question 42

When installing a wireless thermostat, a good location for a temperature sensor would be ____.

Answer 42

on an inner wall about 5' above the floor. | The average location of a normal thermostat.

Question 43

When an HVAC system is set to operate in heating mode, a meter reading should indicate a(n) ____ across terminals R and Y.

Answer 43

open circuit

Question 44

When and HVAC system is operating in cooling mode, a meter reading should indicate a(n) ____ across terminals R and W.

Answer 44

open circuit

Question 45

When troubleshooting an HVAC system, if no voltage is measured across any of the pairs of thermostat wiring terminals, the problem is most likely with the wire connected to terminal ____.

Answer 45

R

Question 46

When troubleshooting a heating system that does not work, if source voltage can be measured in the thermostat, the problem is most likely with the wire connected to terminal ____.

Answer 46

W

Question 47

When measuring voltage across an open switch on a thermostat, expect to read ____.

Answer 47

source voltage

Question 48

If a heating system turns on once jumpers are placed across the proper wiring terminals in the thermostat, the problem is most likely the ____.

Answer 48

wires between thermostat and heating

Question 49

A multistage thermostat will only close its switch to terminal ____ once temperature drops below set point by more than 3 degrees F.

Answer 49

W2

Question 50

A multistage thermostat will only close its switch to terminal ____ once temperature rises above set point by more than 3 degrees F.

Answer 50

Y2

Question 51

A step-down transformer used with a low-voltage thermostat should not have ____.

Answer 51

any electrical loads in series

Question 52

To compare a step-down transformer's secondary side VA rating with the VA of all the electrical loads in its circuit, a technician must add together each load's ____.

Answer 52

current rating

Question 53

In residential applications, live electrical measurements across terminals in a line-voltage thermostat should be ____.

Answer 53

120 Vac or 240 Vac