ACR-108 Midterm Exam (7-21-25) - Mr. Graham

The control voltage that is typically used in split-type residential central air-conditioning systems is 

• 24V

• 48V

• 115V

• 96V

A column of temperature-sensitive fluid rising and falling within a hollow stem in response to a sensed temperature or level of heat intensity best describes the function of a ________.

• thermometer

• thermistor

• snap-disc

• pneumatic control

Most hermetic compressors are cooled by ________.

• suction gas passing through the motor

• using a timed off-cycle to allow the motor to cool

• passing air over the motor

• water running over the compressor shell

System overshoot is the result of which of the following with regard to a heating system?

• The residual system heat increasing the space temperature

• The time it takes for a heating system to start producing heat

• The amount of current flowing through the thermostat

• The amount of heat generated in the thermostat

A pressure switch that has a cut-in pressure of 30 psig and a differential of 10 psig will operate with

• a cut-out pressure of 20 psig.

• an average pressure of 20 psig.

• a cut-out pressure of 10 psig.

• an average pressure of 10 psig.

A low-voltage thermostat normally regulates other controls and does not carry much current, typically around 10 amps or less.

• True

• False

_________ are typically normally closed devices that open their contacts only when the device senses system conditions that are outside the designed operating range.

• Safety devices

• Pneumatic controls

• Rod and tube controls

• Bimetal devices

A ________ is a thin, flexible, movable membrane that is used to convert pressure changes to movement or motion in a control.

• bimetal coil

• snap-disc

• control bulb

• diaphragm

System lag is the result of which of the following with regard to a heating system?

• The amount of current flowing through the thermostat

• The residual system heat increasing the space temperature

• The time it takes for a heating system to start producing heat

• The amount of heat generated in the thermostat

In a “rod and tube”-type control device,

• the rod pushes a mechanical linkage to open or close a valve or set of electrical contacts.

• the mechanical linkage pushes against the tube to open or close a valve or set of electrical contacts.

• the rod, when heated, pushes against the tube to open or close a valve or set of electrical contacts.

• the tube pushes a mechanical linkage to open or close a valve or set of electrical contacts.