HVAC Unit 15-16 Test

___ send information back to the controller in terms of milliamps (mA) or volts.

Active Sensors

___ send information back to the controller in terms of resistance (ohms)

Passive Sensors

T:F Today control output devices can receive signals as either analog or digital

True

Electronic controls are commonly called what

Direct Digital Controls

___ are devices that can measure some type of environmental parameter or a controlled variable and converting this parameter to a value that the controller can understand

Sensors

The temperature in a room is known as the ___ air temperature

Ambient

T:F Modern control systems only have on and off control capability

False

T:F DDC is a control process in which a microprocessor, acting as a digital controller, constantly updates a database of internal information

True

A device called a ___ is used to control the large volume of air in an air conditioner system

Pilot Positioner

___ driers use some of the same products that refrigerant driers use, silica gel or molecular sieve as an adsorbent.

Desiccant driers

___, usually housed internally inside the controller, convert the information from either analog to digital (A/D) or digital to analog (D/A) format.

Signal Converters

___ control systems were used before electronics.

Pneumatic

T:F The very first control system were used to start and stop the various components

True

T:F Controllers are devices that can measure some type of environmental parameter or a controlled variable and convert this parameter to a value that the controller can understand.

False

The __ system actually changes or conditions a signal in three steps

DDC

Controlling the water flow to the room’s needs is called __.

Modulating flow

The controlled environment could be controlled by an array of __ such as dampers, fans, variable-frequency drives.

Controlled output devices

A ___ is either in the pressure reducer or in the downstream side of the system to ensure that the control air pressure does not exceed about 30 PSIG.

Relief Valve

The ___ is the device that responds to a change in conditions

Sensor

In a home air-conditioning system, the ___ is the sensor.

Thermostat

T:F Space temperature is the only temperature that is important in modern systems

False

All control systems can be subdivided into ___, no matter how many controls there are

Control loops

In most system compressors, the compressors are controlled with a ___

Pressure switch

A __ reacts to stop, start, or modulate the flow of water, air, or refrigerant to the system or conditioned space.

Controlled device

Pneumatic controls must have a permanent air supply that is __

Clean and dry

T:F The very first control systems were used to start and stop the various components

True

Thermostat has some small switches in the back that are called ___ switches that allow the technician to set this thermostat up for the particular piece of equipment that it is controlling.

Dip

The pilot positioner has a main air supply that is governed by the ___

Internal diaphragm

In a(n) ___ loop, all changes happen within the loop.

Closed

___ is the part of the digital controller where this information is stored

Memory

Most system compressors provide ___ psig of air pressure to the storage tank

100 to 125

T:F Controllers are devices that can measure some type of environmental parameter or a controlled variable and convert parameter to a value that the controller can understand.

False

Transformers are rated using ___

Volt-amperes

T:F When conditions are correct, the rheostat will pass power through the device onto the system components to be controlled

False

The continuity through a heat relay is checked using a(n) ___

Ohmmeter

T:F When using a ten-wrap multiplier, the reading on the meter must be multiplied by ten.

False

A control can be which of the following:

• Electrical

• Mechanical

• Electrical and mechanical

• All of the above

All

T:F When checking thermostat circuits, and insulated jumper wire is a handy tool

True

Non-power-consuming, or power passing, devices are commonly referred to as ___

Switches

T:F The cooling anticipator in a thermostat is usually an adjustable type

False

T:F If line one of a circuit had a potential of 120V and line two was neutral, the potential voltage (difference) between line one and line two would be zero volts.

False

T:F While troubleshooting a 24V control circuit consisting of a thermostat, a pressure control, and a contactor coil, the technician reads 24V across the thermostat, 0 volts across the pressure control, and 0 volts across the contactor coil. The technician makes the following statements. The following statements are all considered to be true:

• The transformer is burned out.

• The thermostat is open.

• The contractor coil is energized.

False

An electrical diagram showing the approximate location of the components is called a(n) ___.

Pictorial Diagram

A 10-wrap amperage multiplier is used with a(n) ___.

Clamp-on ammeter

A(n) ___ is the easiest diagram to use to follow a circuit. This diagram normally can be studied briefly, and the circuit function should become obvious.

Ladder diagram

An example of a power consuming device would be a(n) ___ while an example of a non power consuming device would be a(n) ___.

Light bulb, single-pole single-throw pole

While checking a simple series 115V circuit containing a fuse, a switch, and a light bulb, the technician’s voltmeter reads 115V across the light bulb socket. The light bulb is not on. He correctly concludes that the ___ is defective.

Bulb

T:F A 120V/24V control transformer has a VA rating of 20. The maximum amperage the transformer will put out is 0.8 amps.

True

The ___ is nothing more than a set of switches

Thermostat

The line side of a switch is the ___

Side the power source is connected to

Electrical controls are divided into two categories: power-consuming and ___

Power-passing

If an air conditioning system is calling for cooling and the compressor is running but the indoor (evaporator) fan is not running, which terminal on the thermostat will the technician most likely check first?

G on the terminal strip

Without ___ voltage, there is no low voltage

High

One way to troubleshoot a(n) ___ on a heating and cooling system is to first turn the fan selector switch to the FAN ON position and see if the fan starts.

Thermostat

T:F The heat anticipator in a thermostat is usually an adjustable type.

True

An electrical power consuming component is also known as ___

A load

T:F When checking thermostat circuits, an insulated jumper wire is a handy tool.

True