Direct digital controls (DDC) operate by:
A) Providing a modulating air pressure in response to monitored conditions.
B) Processing electronic signals with a microprocessor.
C) Providing a varying DC voltage in response to monitored conditions.
D) Turning relay coils on or off to complete circuits.
[Ques. 2] Variable-frequency drives (VFD) reduce the speed of AC motors by:
A) Applying an adjustable magnetic brake to the motor.
B) Controlling the voltage available to the motor, like a light dimmer.
C) Limiting the current to the motor.
D) Controlling the frequency (Hz) of the power to the motor.
[Ques. 3] When operated with the same power source, which induction motor will have a higher RPM: a four-pole motor or a six-pole motor?
A) The four-pole when turning clockwise, the six-pole motor when turning counterclockwise.
B) The four-pole motor will turn faster.
C) The number of poles does not affect the speed of the motor.
D) The six-pole motor will turn faster.
[Ques. 4] The disconnect switch for the unit:
A) Can be the breaker in the power distribution panel feeding the furnace circuit.
B) Should be located within sight of the furnace.
C) Should be attached to the furnace cabinet.
D) Should be located in an easily accessible location, like a utility closet or garage.
[Ques. 5] Electronic control systems operate by:
A) Providing a varying DC voltage in response to monitored conditions.
B) Providing a modulating air pressure in response to monitored conditions.
C) Turning relay coils on or off to complete circuits.
D) Processing electronic signals with a microprocessor.
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