Unit A, Objective 5

What is the primary function of thermostats in HVAC systems?

• To control lighting

• To sense and transmit temperature changes

• To manage humidity levels

• To regulate air pressure

Which feature do electronic thermostats have that electromechanical ones typically do not?

• Mercury switches

• Programmability

• Bimetal coils

• Manual reset buttons

What type of thermostat is used to control modulating process control systems?

• Anticipated multi-stage heat-cool thermostat

• Modulating or proportional thermostat

• Combination fan limit control

• Thermodisk

Which component is NOT part of the modulating thermostat's structure?

• Remote bulb sensor

• Variable resistor

• On/off switch

• Voltage output terminals

How does a combination fan limit controller function in a gas heating appliance?

• Starts and stops the compressor

• Modulates the damper for temperature control

• Starts and stops the furnace fan based on heat exchanger temperature

• Controls the lighting within the HVAC system

What is the purpose of a high-temperature limit on a combination fan limit controller?

• To increase efficiency

• To prevent excessive heat exchanger temperatures

• To reduce energy consumption

• To control humidity levels

What is the consequence of setting the fan cut-out temperature too high on a combination fan limit controller?

• Increases heating efficiency

• May cause fan short cycling

• Decreases system operating costs

• Lengthens fan life

Which type of control is characterized by having a fixed differential and a manual reset button?

• Modulating thermostat

• Encapsulated high-pressure controller

• Oil failure control

• Anticipated multi-stage thermostat

How is true oil pressure measured in an Oil Failure Control (OFC)?

• As the difference between oil pump discharge and atmospheric pressure

• As the sum of crankcase pressure and oil pump discharge pressure

• As the difference between oil pump discharge and crankcase pressure

• As the oil pump discharge pressure alone

What is a critical component of the oil failure control operation?

• Time delay

• Pressure adjustment

• Temperature regulation

• Humidity control