HVAC 6014 - Electric Controls for Heating Systems (Chp 11)

Question 1

The bimetal sensing element consists of a strip made up of two thin layers of metal with:

A) Widely different rates of thermal conductivity
B) Widely different rates of thermal expansion
C) Slightly different rates of thermal conductivity
D) Slightly different rates of thermal expansion
E) Similar rates of thermal expansion

Answer 1

B) Widely different rates of ‘‘thermal expansion’’

NOTE;THERMAL EXPANSION

Question 2

Using electricity for control purposes has the following advantages:

1. It is readily available
2. The wiring is usually simple and easy to install
3. Signals from sensing elements can only produce one output
4. Controller/actuators do not require an air supply

A) 1, 2, 4
B) 1, 2, 3, 4
C) 2, 3, 4
D) 1, 3, 4
E) 1, 2, 3

Answer 2

A) 1, 2, 4
NOTE:
AVAILABLE
SIMPLE AND EASY
DO NOT REQUIRE AIR SUPPLY

Question 3

A transformer is a device that is used to change:

A) DC voltage from one value to another
B) DC amperage from one value to another
C) Both AC and DC voltages
D) AC voltage from one value to another
E) AC amperage from one value to another

Answer 3

D) AC voltage from one value to another

Question 4

In a basic electrical control system, the device that senses a drop in air temperature is called the:
A) Humidistat
B) Thermostat
C) Regulator
D) Final controlled device
E) Pneumatic temperature sensor

Answer 4

B) Thermostat

Question 5

On-off thermostats are equipped with a/an:

A) Low voltage switch
B) High voltage switch
C) Open contact switch
D) High temperature switch
E) Low temperature switch

Answer 5

C) Open contact switch

Question 6

When a temperature below set point is sensed, the thermostat:

A) Controls a transformer
B) Operates a switch
C) Starts the fan
D) Opens to send an electric signal
E) Closes to send an electric signal

Answer 6

E) Closes to send an electric signal

NOTE:CLOSES TO SEND

Question 7

An example of a heating system controlled device would be a:
A) Thermostat
B) Damper motor
C) Hot water boiler
D) Radiator
E) Steam boiler

Answer 7

B) Damper motor

Question 8

Thermostats may be classified according to their:

A) Temperature range
B) All of the above
C) Application
D) Type of temperature sensing element
E) Type of control action provided

Answer 8

B) All of the above

Question 9

A valve that can be used for either mixing or diverting service is:

A) Fuel valve
B) Float valve
C) Check valve
D) Radiator valve
E) Three way valve

Answer 9

E) Three way valve