HVAC Controls and Thermostats

Question 1

What type of thermostat uses a bimetallic strip as its primary sensing element?

Accepted Answer

Mechanical thermostat

Answer

Mechanical thermostats use a bimetallic strip that physically bends with temperature changes to make or break electrical contacts.

Question 2

What is the 'deadband' in thermostat operation?

Accepted Answer

The temperature range between heating and cooling setpoints where neither system operates

Answer

The deadband is the neutral zone between heating and cooling setpoints that prevents simultaneous heating and cooling operation.

Question 3

What does DDC stand for in building automation and HVAC controls?

Accepted Answer

Direct Digital Control

Answer

DDC (Direct Digital Control) uses microprocessors to directly monitor and control HVAC equipment using digital signals and algorithms.

Question 4

Which control type continuously modulates output between 0% and 100% in proportion to the deviation from setpoint?

Accepted Answer

Proportional control

Answer

Proportional control continuously varies output based on how far the controlled variable deviates from setpoint, unlike simple on/off control.

Question 5

What is the primary purpose of a heat anticipator in a mechanical thermostat?

Accepted Answer

To prevent temperature overshoot by shutting off the furnace slightly early

Answer

The heat anticipator pre-heats the thermostat's sensing element to signal the furnace to shut off before the setpoint is fully reached, preventing overshoot.

HVAC Practice Test

HVAC Practice Test

HVAC Controls and Thermostats