FC FC Electrical Components & Controls 2

Question 1

Which terminal on a conventional thermostat wiring system carries the 24V common (return) signal?

Accepted Answer

C terminal

Answer

The C (common) terminal completes the 24V circuit from the transformer secondary, providing a return path for connected devices.

Question 2

What is the purpose of the pressure switch on an induced-draft furnace?

Accepted Answer

To confirm the inducer motor is creating proper draft before allowing ignition

Answer

The pressure switch verifies that the draft inducer has established proper negative pressure before the control board allows the ignition sequence to proceed.

Question 3

A furnace control board flashes a fault code 3 times (pause) 1 time. How should a technician interpret this?

Accepted Answer

The code is 31 and corresponds to a specific fault in the manufacturer's chart

Answer

Furnace control boards use flash codes where the number of long flashes followed by short flashes encodes a specific fault code (e.g., 3-1 = code 31).

Question 4

What is the function of the blower door interlock switch on a furnace?

Accepted Answer

Cuts power to the furnace if the blower compartment door is removed

Answer

The interlock switch de-energizes the furnace when the blower door is open, preventing operation with exposed moving parts and electrical components.

Question 5

What type of motor is most commonly used in high-efficiency furnace blowers for variable-speed operation?

Accepted Answer

ECM (electronically commutated motor)

Answer

ECM motors use permanent magnets and electronic controls to vary speed efficiently, reducing energy consumption compared to PSC motors.

(FC) Furnace Installation and Maintenance Certification Practice Test

(FC) Furnace Installation and Maintenance Certification Practice Test

FC FC Electrical Components & Controls 2